Reproductive global regularities. There is yet another kind of global regularity, because there is another kind of non-basic, or derivative, substance that can work together with space as an ontological cause to generate global regularities, namely, reproductive cycles. Such ontological causes derive from material and structural causation, but reproductive cycles work together with space to generate what are, by far, the most spectacular global regularities, namely, evolutionary change.

The ontological cause of reproductive global regularities is a derivative substance. It is constituted by a material structure that uses free energy to do work. But reproductive cycles are basically different from material structures, because their essential nature as a (derivative) substance has a temporal structure. Each reproductive cycle is, as the name suggests, a whole cycle of changes (exhibiting various irreversible structural global regularities), and thus, it takes place over a period of time.

There is an existential aspect to reproductive cycles, as there is to any substance, because they endure through time. But in the case of reproductive cycles, endurance through time does not come directly from matter enduring through time, but rather indirectly, because it also depends on how one cycle gives rise to another cycle as time passes.

Since each cycle in such a sequence takes time to be completed, the cycle itself does not exist fully at any moment. What does exist fully at each moment is the (complex) material structure that is going through the cycle (or what will be called the "primary structure"), and since it is the ontological cause of the irreversible structural global regularities that are the cycle of changes, the whole cycle is implicit in what exists at each moment as it is present.

Reproductive cycles have, in other words, more basic ontological causes. In addition to space (spatial causation), each series of cycles depends on a thermodynamic flow to supply the free energy (material causation) and a complex material structure that uses free energy to generate the cycle of changes (structural causation). Moreover, since reproductive cycles derive from more basic forms of ontological causation only with the addition of a temporal structure to their essential nature, that is, as a cycle of changes, time as well as space might also be said to be an ontological cause. But in any case, since a cycle of changes is what a complex material structure ( that is, the primary structure) generates, reproductive cycles themselves endure through time like substances.

Though their endurance through time makes it possible for reproductive cycles to work together with space as an ontological cause, they would not be able to generate a new kind of global regularity (that is, one that is basically different from the irreversible structural global regularities, or “structural effects,” generated ontologically by the complex material structure), if the complex material structure did not generate two basically different kinds of structural global regularities during each cycle, one that reproduces the complex material structure and the other that does non-reproductive work. The inclusion of reproduction along with other structural effects is what makes them reproductive cycles, rather than mere cycles, and as we shall see, having both kinds of structural effects is what makes reproduction the basic cause of natural selection and, thus, of evolutionary change..

Primary structures. The material structures going through reproductive cycles are ordinarily called "organisms" or "reproducing organisms," but since we will be recognizing a series of levels of part-whole complexity in organisms, I will use a technical term, "primary structure," to refer to the material structure that is responsible for the reproductive cycles being discussed.

Primary structures (including ordinary organisms) are complex material structures, because they are made up of many different parts each serving as a structural cause of a different structural global regularity during the reproductive cycle. But primary structures are a distinctive kind of complex material structure, because they are also the ontological cause of structural global regularity in which the entire, complex material structure is reproduced. That is, in addition to various forms of non-reproductive work, primary structures normally construct one or more new primary structures of the same kind to go through the next reproductive cycle alongside one another. In other words, in addition to surviving, organisms also reproduce.

The basic ontological effect of reproductive cycles and space is gradual change in the direction of greater power.

Because they reproduce, organisms tend to multiply in space as their reproductive cycles follow one another in time, and thus, since the organisms are all contained in the same region of space, their population growth causes a scarcity of free energy (if nothing else). Not all the organisms can continue going through reproductive cycles. But it is not just chance which ones continue, because they do non-reproductive work as well as reproduce. There is a natural selection that favors those organisms whose non-reproductive work promotes their reproduction, and thus, there is a change in the whole region in which organisms become increasingly powerful in controlling conditions that affect their reproduction.

Reproduction is, in other words, the basic cause of natural selection. Evolutionary change does not depend on changes in the environment. Insofar as natural selection is caused by reproduction, rather than environmental change, evolution is, as we shall see, a gradual change in the direction of an optimal state, or “natural perfection.” Gradual evolution is, therefore, progressive.

Besides “gradual evolution,” however, there is another global regularity caused by reproductive cycles, namely, “revolutionary evolution,” by which one stage of gradual evolution gives rise to another in a determinate series of evolutionary stages. The ontological cause of this aspect of reproductive global regularities is higher levels of part-whole complexity in the structures of the organisms going through reproductive cycles, that is, by higher levels of part-whole complexity in their primary structures.

Organisms are just complex material structures, or "primary structures," and thus, it is possible for organisms that have become nearly optimal by going through reproductive cycles to become bundled together as so many different structural causes that go through reproductive cycles as a whole, complex material structure, that is, on a higher level of part-whole complexity.

The advent of such a higher level of part-whole complexity in the structures of organisms is a revolutionary change, because it begins a new stage of gradual evolution, or change in the direction of natural perfection. The organisms that are evolving at the new stage start off simple, uniform and weak, and they gradually become increasingly complex, diverse and powerful. But since they have structures with a higher level of part-whole complexity, they are inherently more powerful in controlling relevant conditions than those at the previous stage, and their gradual evolution will make them far more powerful than the organisms that evolved at previous stages.

Since they are caused by higher levels of part-whole complexity in reproducing organisms, stages of evolution can occur only in a certain sequence, and thus, the overall course of evolution is an inevitable series of evolutionary stages. Since those stages are also change in the direction of increasing power, the overall course of evolution is progressive in a far grander way than the gradual evolution that occurs at each stage, for it proceeds by one revolutionary change after another in the direction of ever greater power to control relevant conditions.

(It should be noted at the outset that there are several sequences of stages of evolution in the overall course of evolution. The basic stages are caused by higher levels of part-whole complexity in primary structures, but there are other sequences of evolutionary stages, because new stages of evolution can also be caused by higher levels of part-whole complexity in secondary structures, or structures that are set up or maintained by the same kind of primary structure, including, as we shall see, levels of part-whole complexity in brain structure and levels of part-whole complexity in linguistic structures, such as arguments.)

Comparison to Darwinism. These reproductive global regularities, both gradual and revolutionary, are the ontological effect of reproductive cycles and how they add up in space as time passes. I will call it "evolution by reproductive causation." But it is basically the "mechanism" that Darwin discovered, the mechanism of random variation and natural selection. However, by deriving reproductive causation from spatiomaterialism (and the kind of space and matter required by the basic laws of physics), evolution is explained ontologically, as a global regularity. That will show not only that there are many aspects of evolution that are not currently recognized, but also that those aspects are inevitable in all spatiomaterial worlds like our own, that is, (conditionally) ontologically necessary.

At the outset, therefore, it may help put what is at issue in perspective to compare reproductive causation with Darwin’s “mechanism,” especially the current understanding of his mechanism. Evolutionary biologists tend to think of natural selection as an empirically discovered tendency, for that is how they defend their explanation of evolutionary change from creationists. But as we shall see, much more can be known about evolutionary change when it is explained ontologically.

Reproductive causation departs from contemporary Darwinism in two ways. On is its explanation of gradual evolution, and the other is its recognition of revolutionary evolution.

The basic cause of evolutionary change was discovered by Darwin as he thought about what happens in populations of organisms as they reproduce themselves. He saw that if variations on traits occur randomly in such organisms, and if those traits are inherited by their offspring, evolutionary change could occur simply as a result of the greater reproductive success of those organisms that have traits that are useful. This is what happens in breeding plants and animals, but he called it “natural selection,” because it occurs in nature without human intervention. Over time, the natural selection of random, heritable variations gives species traits that adapt them to their environments.

Such adaptations depend only on efficient causes, and thus, Darwin showed how evolution could happen in a materialist world, where everything is caused by how bits of matter move and interact with one another over time. It removed any need to appeal to a "designer" in explaining the wonderful functions found in the natural world. But there is considerable dispute about the status of Darwin’s “mechanism” and, thus, about the explanations of evolutionary change based on it.

Views range from thinking of Darwin’s mechanism as a principle or peculiar law of nature to thinking of it as a mere tautology (the survival of the fittest, where “fitness” is defined as surviving). Somewhere between them comes the belief that it is just a pattern for giving a kind of historical explanation of the evolution of traits, which is filled out by mentioning all the contingent details by which natural selection worked in any particular case. More recently, the computer analogy has led some to call it an algorithm (see Dennett 1995). And others take Darwin's mechanism to be a basic tenet that naturalists simply accept, helping to define “naturalism” (see Rosenberg 1996, p. 4).

However Darwin’s mechanism is characterized, contemporary Darwinists universally deny that there is any reason to believe that evolution is progressive. Most are wedded to an interpretation of Darwin’s mechanism that denies there is anything necessary about the overall course of evolution or about the species that evolve. It would all happen differently, if evolution were started over and allowed to play itself out again. I will call this prevailing commitment to the contingency of evolution accidentalism. The grounds for accidentalism come down to two main factors.

First, environmental change is what is thought to cause natural selection. If selection pressures are imposed on species by changes in the environment whose causes are external to evolution itself, the course of evolution cannot be predicted by Darwin’s mechanism alone, and in the words of Stephen Jay Gould (1976) , “Evolution by natural selection is no more than a tracking of . . . changing environments by differential preservation of organisms better designed to live in them”. (Gould, “Darwin’s Untimely Burial”, Natural History, Vol. 85, No, 8, 1976; reprinted in Ruse, 1989, p. 98.)ⁱ

Elliot Sober (1984, p. 174) endorses this view of the effect of natural selection as “‘tracking’ the environment,” and he attributes it to Lewontin (1978) pp. 156-169. Even Richard Dawkins (1986, p. 179) agrees that evolution “constantly ‘tracks’ the changing environment.”

Second, when a change in a species’ environment occurs, there is no guarantee that the best adaptation will occur in response. Natural selection operates on random variations, and it has only whatever variations happen to be available at the time from which to select. There may be other variations which would be better, but since they are not tried out (or tried out only later, after another variation has already evolved), they cannot be selected.

As Michael Ruse (1986, p. 19), a leading philosopher of biology, puts it, “Given a need, the option taken to satisfy it is a function of what you have at hand, rather than what the perfect answer would be.”

According to E. Sober (1984, p. 174), evolution does the best it can with the random variations it has when the environment imposes a new selection pressure, but it is just a makeshift response to the exigency of the moment. See also Philip Kitcher, 1985, pp. 213-226. The most famous example of this contingency is, thanks to Gould (1980), the Panda’s thumb.

The upshot of accidentalism is that there is nothing necessary about the species that come to exist or the course of evolution. By seeing evolution as tracking environmental changes, accidentalists are taking the traits that accumulate in any species to be a record of the history of the environmental changes that happened to occur. After adapting to one environmental change, new traits are acquired that adapt the species to the next, and thus, the nature that a species now has depends on a series of selection pressures that could have been different.

Contemporary Darwinism makes it seem, in Kauffman’s (1993) words, that evolution merely “cobbles together jury-rigged contraptions” (p. 3). It sees “organisms as overwhelmingly contingent historical accidents, abetted by design” (p. 26). Or as Ruse (1986, p. 93) says, “you could as well have one organic state as another”.

As Mark Ridley (1985) explains, “Evolution is continually going on; the traits of lineages continually change. What will define a group at one time may not define it at another. The traits defining groups are temporarily contingent, not essential. Biological groups do not have Aristotelian ‘essences.’” (Reprinted as “Principles of Classification,” in Ruse, 1989, p. 178.)

E. Mayr, insisting that evolution is “opportunistic and unpredictable,” holds that “If evolutionists have learned anything from a detailed analysis of evolution, it is the lesson that the origin of taxa is largely a chance event.” He cites such factors as “the genetic composition of the founding population, the special internal structure of its genotype, and the physical as well as biotic environments that supplies the selection forces of the next species population.” (“Probability of Extraterrestrial, Intelligent Life,” reprinted in Ruse, 1989, p. 283.)

Richard Lewontin suggests that “[a]s far as we know all living organisms are connected by an unbroken chain of historical contingency,” in “The Shape of Optimality”, collected in Dupré (1987, p. 158).

Michael Ruse (1986, p. 20) says “there is nothing in selection itself which encourages progressionism” because “[w]hat counts is reproduction, here and now and in the immediate future. If the simpler, less intelligent form can do it better—and it often can—then so be it.”

The appearance that evolution is progressive has recently been given an accidentalist explanation by Gould (1996). He argues that there is an overall change in the direction of greater complexity, because starting with the simplest, that is the only direction that evolution can go.

What undercuts the traditional belief in “fixed species” is, therefore, the role of contingent factors in evolution, for they show that species will lack the necessity of natural kinds or essences.

Evolution by reproductive causation is not, however, accidentalist, but rather progressive. Nor does this progressivism abandon Darwin's mechanism.

It accepts the consensus among Darwinists about the three elements involved in the evolution of a population of reproducing organisms by Darwin’s mechanism. It agrees that there must be random variations in the traits of the organisms, that such traits must be heritable by their offspring, and that there must be a natural selection by greater reproductive success of members with certain traits.

But instead of assuming that that natural selection is due to externally caused changes in the environment, this ontological explanation of Darwin’s mechanism implies that natural selection is, in addition, due to the scarcity caused by reproduction itself. As organisms reproduce, their population increases, and the resources they need becomes scarce. Only some of them can succeed in reproducing. But it is not just chance which ones succeed, since different varieties have different powers to control conditions in the world. The survivors tend to be those that are more powerful in some relevant way.

Moreover, if the scarcity due to their own reproduction is a cause of natural selection, it must be the main cause, for there is one resource that is always eventually in short supply: free (or usable) energy. Thus, evolutionary change would occur, not just in response to changes in the environment, but continuously. As we shall see, such a steady cause has a continuous effect, and there is inevitably a gradual accumulation of traits in the direction of an optimal state, which I will call “natural perfection.”

This view of evolution will be called “reproductive causation,” because it takes reproductive cycles and how they add up in space over time to be the ontological cause of evolution. In other words, it takes the reproduction of organisms to be the ultimate cause of natural selection, for that is why their non-reproductive work is increasingly powerful.

Though this is different from the explanation of evolution given by contemporary Darwinists, it is worth noting that it may have been Darwin’s own view. In The Origin of Species, he introduced natural selection by appealing to Malthus’ theory of population growth—which holds that, while human population tends to increase by a geometrical progression, their resources increase by a mere arithmetical progression. Since it suggests that those who are best able to survive are the ones most likely to succeed in reproducing, Darwin called natural selection a “struggle for survival.” It was Spencer who called it the “survival of the fittest.”

Whatever it is called, the point is that reproduction itself is what puts members of a species at odds with one another. The cause of evolution is internal. Organisms need energy, and in any environment, reproduction will eventually cause a scarcity of usable energy, if nothing else, for it is a physical fact that the usable energy in any finite region of space is finite. Thus, even without externally caused changes, evolution would take place, whatever the environment. Thus, reproductive causation implies that accidentalism is false.

Reproduction is also the ultimate cause of stages of evolution, the other main departure from contemporary Darwinism. Stages of evolution are caused by the capacity of higher levels of part-whole complexity in the structures of the organisms to go though reproductive cycles as a whole, for once they occur as random variations, they impose natural selection of themselves and gradually become more powerful.

Contemporary Darwinists recognize what they call “punctuated equilibria” in the fossil record of evolution, but they have no general explanation of their cause. On the contrary, they are taken as evidence that Darwin’s mechanism is not the only cause of evolutionary change.

By tracing natural selection to its ontological causes, however, we can see why such revolutionary episodes in the course of evolution are inevitable. When higher levels of part-whole complexity that make organisms more powerful can occur as a random variation at all, they are inevitable, because they will eventually be tried out and, when they are, they will impose natural selection on themselves by their own reproduction, beginning a new stage of gradual evolution. Each stage is gradual change in the direction of increasing power for organisms of its kind, and thus, the series of stages is a step-like change in the direction of the increasing power of life itself.

By following out what is ontologically necessary about evolution in a spatiomaterial world like ours, therefore, we shall derive novel implications for almost every branch of natural and social science. And what is more, the progressivism of evolution provides an explanation of the nature of goodness.

These two reproductive global regularities are explained in greater detail in the following two sections.

The next section, gradual evolution, will explain the nature of the new (derivative) ontological cause (reproductive cycles) more completely than the foregoing sketch and use it to show the inevitability of a long term, gradual change in the direction of greater power. It will show that the outcome of such change is “natural perfection” for both organisms and the ecology of which they are part.

The following section, revolutionary evolution, deals with a consequence of recognizing reproductive cycles as an ontological cause, which is not even suspected by Darwinists. It will explain how space combines with reproductive cycles in a new way (by making possible higher levels of part-whole complexity in the structures of organisms) to cause more radical changes in evolution, each of which begins a new stage of gradual evolution. Thus, reproductive causation implies that evolutionary change involves an inevitable series of stages of evolution, and this section will describe in detail the essential natures of the organisms that evolve at each stage, which includes, by far, the bulk of the implications of ontological philosophy

Reproductive causation: Gradual evolution. The first of the two main kinds of reproductive global regularities is gradual evolution, and it will be explained here by considering, first, its Ontological cause, the existence of reproductive cycles in closed or isolated regions of space, and then, its Ontological effect, a global regularity in which evolutionary change leads gradually in the direction of an optimum, which will be called “natural perfection” because it makes the most of what is possible in a spatiomaterial world. In other words, reproductive causation implies that gradual evolution is progressive.

Though I have already suggested why gradual evolutionary change is ontologically necessary (in the introductory section of Reproductive global regularities), there is more to be said about its ontological cause. First, in order to show that reproductive cycles are an ontological cause, it is necessary to show how they derive from space, matter, and the ontological causes of simpler global regularities. Second, in order to explain what gradual evolution involves, it is necessary to explain what is meant by “natural perfection” and to show how this ontological cause generates gradual change in the direction of natural perfection in both the organisms and the ecology.

Ontological cause: reproductive cycles. What constitutes the ontological cause of gradual evolution is a way that all the simpler ontological causes of global regularities work together. Their combination yields a kind of (derivative) substance with an odd nature. It is the reproductive cycle. It is basically just an organism with heritable traits that normally reproduces itself during its lifetime. But explaining the derivative substances ontologically will show the necessity and character of the global regularities they cause.

Reproductive cycles are, in effect, “substances” that derive from material and structural causation. Enplaning that will show how reproductive cycles are reduced to spatiomaterialism, since we have already seen how those more elementary ontological causes are reduced to spatiomaterialism..

Material global regularities are involved, because what is going on in reproductive cycles is the use of free energy to do work, that is, to make things happen that would not otherwise happen. As we shall see, most of the relevant free energy is supplied in the way sketched earlier, that is, by the radiation from a star. That is a thermodynamic flow of matter toward evenly distributed heat, and when it is intercepted by a planet in orbit around the star, it can be used to fuel reproductive cycles. Cycles of reproduction are irreversible processes, though each reproductive cycle involves many structural global regularities.

Structural global regularities are involved because what uses the free energy to do work are structural causes. There are material structures that coincide with the thermodynamic flow of matter toward evenly distributed heat, and the ensuing motion and interaction results in certain specific effects, which are events that would not otherwise occur. This is an ontological explanation of how efficient causes produce their effects, as we have seen in the case of dispositions. In discussing structural global regularities, we saw that structural global regularities entail efficient-cause connections. What makes such structuring of the tendencies to kinetic energy and randomness into a new ontological cause is how structural causes are combined in the constitution of reproductive cycles.

Reproductive cycles. What makes the reproductive cycle a new ontological cause is the kind of material structure that generates this structural global regularity (which is ordinarily called an "organism"). It is a kind of material structure that generates a cycle of irreversible processes that includes both reproduction and non-reproductive work.

The organism. The organism is a complex material structure, for it includes a number of material structures bundled together as various structural causes. But in addition to the distinctive structural global regularity that each such a structural cause generates, there is a structural global regularity in which the material structure as a whole is reproduced, making the whole process generated a reproductive cycle.

Such material structures will be called "organisms," or "reproducing organisms, when they go through reproductive cycles on their own. But after a few stages of evolution, as we shall see, there may also be a few levels of part-whole complexity of such material structures within the reproducing organism, and so it will be useful to refer to material structures of this kind as "primary structures." That is, primary structures are complex material structures that are able to reproduce themselves, and the use of this technical term will make it easier to describe the structures of organisms at later stages of evolution.

Organisms (and primary structures) generate, therefore, two kinds of structural global regularities during a reproductive cycle. Each structural cause that is bundled together in the organism usually generates a different kind of structural global regularity. But the organism can also generate a structural global regularity as a whole in which it reproduces itself as a whole, including all the structural causes bundled together in it. In order to keep these two radically kinds of ontological effects of its structural causes straight, I will call the former “non-reproductive work” and the latter “reproductive work.”

I will call the structural global regularities generated by structural causes "structural effects" in order to have a simpler way of referring to them.

In organisms (and primary structures generally), many structural causes are bundled together, and since the structural global regularities that each generates involves a connection between an efficient cause and its effect, we can also say that different efficient-cause connections are bundled together in the organism. But that means that the structural cause is not just an ontological cause, but also an efficient cause, for its inclusion in the structure of the organism is sufficient to bring about the effect during the reproductive cycle. Such an effect is simply the difference that the structural cause makes to what tends to happen (in the organism, its behavior, or in the environment as a result of its behavior) because of the structural global regularity it generates. (Or as the technical formula for our ordinary notion of efficient cause goes, it is a non-redundant member of the set of conditions in the organism that is sufficient for the effect.) Such an effect is what I will mean by "structural effect."

Talk of “structural effects” ignores the difference between the material structure as the ontological cause of the structural global regularity and the inclusion of the material structure in the organism as an efficient cause (along with other conditions) of its occurrence during the reproductive cycle. But that is useful in describing organisms, because different parts of the organism are responsible for different structural global regularities and, thus, different structural effects.

The difference between the reproductive work and non-reproductive work of structural causes can, therefore, be put in these terms. Since the structural effect is the work done by the structural cause in generating a structural global regularity, the two radically different kinds work that are essential to organisms (and primary structures) can also be described as the organism's “reproductive structural effect” and its “non-reproductive structural effects.”

This will be useful, because in all organisms (and primary structures), including the most basic, it is not only the organism as a whole that has both a reproductive and non-reproductive structural effect. Each of the structural causes bundled together in the organism has both a reproductive and non-reproductive structural effect. In fact, the reproductive structural effects of the parts is what enables the organism to reproduce as a whole, for it is a process in which each part reproduces itself.

The non-reproductive structural effects of the material structures bundled together in an organism (or primary structure) are often called the "traits" of the organism. But notice that when traits are explained ontologically, their heritability by offspring is entailed. Since traits are non-reproductive structural effects of the material structures bundled together in organisms, they are necessarily inherited by offspring, because such parts of organisms (and primary structures) also have reproductive structural effects as part of the reproductive work by which the organism as a whole reproduces.

The cyclic structural global regularity. In order for reproductive cycles to exist, however, organisms must actually go through cycles in which they do both their reproductive and non-reproductive work. It is not enough for their material structures to endure though time without doing both kinds of work.

When structural causes are bundled together spatially as an organism, a number of different non-reproductive structural effects are bundled together. But these structural effects do not necessarily occur at the same time. The various structural causes often (though not always) have their non-reproductive structural effects at different times. But to hold that the organism goes through a cycle is to hold that its parts have structural effects that ultimately put the organism back in much the same position where it began, so that it can go through another cycle. That means that the bundle of structural effects has a temporal structure as a whole. Thus, not only are the structural causes bundled together in space as a complex physical organism, but their structural effects are combined in time as a cycle. It is a cycle of changes.

What makes the cycle a reproductive cycle, however, is that at some point during the cycle, the organism is reproduced. That is, one or more additional organisms of the same kind are constructed and put in a position to go through reproductive cycles side by side. The reproduction of the organism as a whole is essential to reproductive cycles being a new kind of derivative ontological cause.

In all the basic organisms, as we shall see, reproduction depends on each structural cause bundled together in them having a reproductive structural effect as well as a non-reproductive structural effect. (This is rather straightforward in the case of bacteria and protists, but it also holds in a more complicated way for multicellular organisms, as we shall see.)

Notice that crystals do not go through reproductive cycles of this kind. The reason crystals are sometimes said to go through reproductive cycles is that, as each molecule is added to the growing crystal, the structure required for the addition of another molecule is created, enabling the processes to be repeated. But this is not the kind of reproductive cycle that is an ontological cause of reproductive global regularities, because the crystal is not an organism (or primary structure) by our definition. It does not have a non-reproductive structural effect distinct from its reproductive effect, not to mention that with just one structural cause, it cannot be a bundle of structural causes at all.

Natural selection. Reproductive global regularities are caused ontologically by space and reproductive cycles (as a derivative ontological cause), because reproductive cycles add up in space over time to natural selection. That is, as they endure through time in the region, they reproduce, and since their own population increase makes free energy (or other resources) scarce, they impose natural selection on themselves.

Reproductive cycles endure through time like substances because they are cyclic. Each cycle begins a new cycle, and thus, the cycles have a continued existence.

Unlike basic substances, however, derivative substances can be destroyed. But since there is both a spatial and a temporal aspect to reproductive cycles, there are two ways that this kind of derivative substance can cease to exist. A cycle can go out of existence either because the material structure of the organism going through the reproductive cycle is destroyed, or because the organism is unable to generate its entire cycle of structural effects. But as long as they do not go out of existence, they are like substances, enduring through time.

As reproductive cycles, however, they also multiply in space. Endurance through time also involves, in the case of reproductive cycles, the reproduction of the organism going through them. That is, in addition to reproducing in time as one cycle follows another, they also reproduce in space as additional organisms of the same kind are constructed.

Reproductive cycles would not be a new kind of (derivative) ontological cause, if all they did was endure through time, for then they would be a mere cyclic irreversible structural global regularity, like a motor. The reproduction of the organism is what makes them a new derivative ontological cause.

Space is the other ontological cause of evolution, along with reproductive cycles.

Spatial causation is the only simpler kind of global regularity that has not been mentioned thus far in explaining the ontological cause of evolution. But spatial causation is one of the ontological causes of every global regularity, because the wholeness of space is what makes the motion and interaction of bits of matter in a region add up over time. And adding up in space to natural selection is just another such role for spatial causation.

In causing material and structural global regularities, however, the structure of space within the region was relevant in another way as well. Its geometrical structure was needed to explain why potential energy tends to become kinetic energy and why kinetic energy tends to become randomly distributed heat. And structural global regularities depend on the geometrical structure of space not only because it helps constitute material structures (that is, material objects with a geometrical structure), but also because it enables them to move around in space without changing their geometrical structures.

In the case of gradual evolution, by contrast, the geometrical structure of space within the region is not directly relevant. It is only the wholeness of space that works together with cycles of reproduction to constitute reproductive global regularities. Thus, the role of space as an ontological cause of evolution depends only on the fact that all the parts of space in the region fit together uniquely as a whole, much like how it worked together with matter to cause the conservation of matter.

Being contained by space makes reproductive cycles add up in a unique way as time passes. Since the continued existence of reproductive cycles entails the multiplication of reproductive cycles in space, expanding the population of organisms, it combines with the space that contains them to cause ontologically a scarcity that imposes natural selection on them.

Though the total matter in any isolated region of space does not change, there is a way that push comes to shove when some of the matter constitutes reproductive cycles. As the organisms going through them reproduce themselves, generation after generation, the reproductive cycles not only endure through time, but also multiply in space, and thus, the population of organisms grows. But the matter in the closed or isolated region must add up arithmetically in space as time passes, that is, as a total that does not change over time (according to the principle of the conservation of matter). Though some of the matter in the region must exist in the form of free energy in order for material structures to do work of any kind, there is only a finite thermodynamic flow of matter from potential energy through kinetic energy (and photons) to evenly distributed heat in any isolated region of space, such as a planetary system or the surface of a planet. Thus, as reproductive cycles multiply in space, scarcity of free energy, if nothing else, will eventually limit the number of reproductive cycles that can continue to exist in the region. Some reproductive cycles will have to come to an end.

In other words, organisms going through cycles of reproduction impose natural selection on themselves. That is how the wholeness of space works together with reproductive cycles to generate a new kind of global regularity. It is simply how reproductive cycles add up in space as time passes.

To be sure, it is natural selection, and not just random selection, because the organisms are not only reproducing, but also doing non-reproductive work which can control conditions that affect reproduction. Those differences among organism are, as we shall see, why natural selection leads to a gradual change in the direction of natural perfection. What makes such variations among organisms possible is that organisms have non-reproductive as well as reproductive structural effects. But what forces a selection to be made at all is their reproduction in space as well as time.

Random variations. This explains all but one of the three elements generally assumed to be part of Darwin’s mechanism. Since heritable variations and natural selection are entailed by the nature of reproductive cycles as an ontological cause, only random variations remain to be explained. There must also be random variation in the organisms in order for natural selection to cause evolutionary change. But random variations are due to another fact also implicit in the nature of reproductive cycles as a ontological cause.

What makes variations in the traits of organisms possible is the fact that organisms (and primary structures) are complex material structures, that is, that they are bundles of various kinds of structural causes. If different varieties of structural causes can be bundled together as a complex material structure at all, they can be bundled together in different ways. That is, different bundles can include different kinds of structural causes. New structural causes can be added, both new kinds and additional particular material structures. And the same structural causes can even be bundled together in different ways. The part-whole complexity inherent in structural causes being bundled together as organisms makes an enormous range of kinds of reproductive cycles possible.

The possibility of random variations is actualized in the simplest organisms, because the global regularity caused ontologically by their material structures is merely a tendency. The structural global regularity that they generate includes the construction of imperfect copies as well as perfect copies of their material structures, thereby introducing random variations.

Material structures have their ontological effects by how they channel the thermodynamic flow of matter toward evenly distributed heat. It depends on how the geometrical structures of the material objects involved coincide with the geometrical structures inherent in the thermodynamic flow of matter toward evenly distributed heat (the geometrical structure of potential energy being converted into the kinetic energy of objects and the geometrical structure of the nonrandom distribution of their causally relevant factors becoming random). Thus, when various material structures are involved (such as an organism and the many parts used to construct copies of it) or free energy is supplied to them in various ways (for example, by radioactive decay as well as chemical energy and the usual photons), what is ontologically necessary about the future may be only a tendency. In particular, the structural global regularities generated by simpler organisms include the construction of imperfect copies as well as perfect copies of their complex material structures. The imperfect copies will tend to resemble the structure of the organism being reproduced, but there will be random variations on it.

This is not to say that structural global regularities, as global regularities, are inherently probabilistic. With the addition of other material structures, it is possible to ensure that no errors occur in reproduction, as in some higher organisms. Reproduction is imperfect in simpler organisms because their material structures cannot control all the structural causes that may be relevant to what happens. The structural global regularity includes various different outcomes with different probabilities. In higher organisms, where reproduction is infallible, special mechanisms are required to introduce random variations.

Darwin’s mechanism as a consequence. Thus, the way that reproductive cycles add up over time in the wholeness of space includes all three of the elements generally considered essential to Darwin’s mechanism (natural selection, heritable traits, and random variations).

The bundles of structural causes that generate reproductive cycles as structural global regularities make up the populations of reproducing organisms in which Darwin’s mechanism is assumed to be at work.

Natural selection is caused by how reproductive cycles add up in space over time, that is, by the scarcity, due to population growth, that requires some reproductive cycles to come to an end.

Traits are inherited by offspring, because the traits are the non-reproductive structural effects of the structural causes bundled together as organisms and those same structures are what is copied in reproduction.

And there are random variations on the traits of organisms, because reproduction is a structural global regularity that involves only a tendency to make perfect copies (or there are mechanisms for introducing random variations).

All three elements of Darwin’s mechanism are entailed in the ontological cause of evolution as a reproductive global regularity.

It may seem paradoxical or even perverse to take reproductive cycles, rather than reproducing organisms, to be the ontological cause that helps constitute the reproductive global regularities. Organisms are three dimensional objects, which endure through time like other substances, whereas reproductive cycles are four dimensional objects, which endure through time only in the sense that the changes involved are cyclic and can go indefinitely. And since reproductive cycles are derivative substances, constituted by reproducing organisms (and a thermodynamic flow of matter toward evenly distributed heat), reproducing organisms do work together with space to cause ontologically the same reproductive global regularities.

There are two reasons for preferring to think of reproductive cycles as the ontological cause of evolution (along with space). The first is that reproductive global regularities are fundamentally different from simple structural global regularities, and the source of that difference is that reproduction occurs cycle after cycle (for it is the scarcity due to their population increase that imposes natural selection on them). And since an ontological cause is something that endures through time like a substance (or a basic relationship among substances), what causes evolution ontologically is the continued existence of reproductive cycles, not just the continued existence of reproducing organisms. What endure is a series of four dimensional objects with the property of multiplying in space.

The other reason has to do with the nature of the ontological effect. What changes in the entire region, as we shall see, is the kinds of reproductive cycles. Though these cycles are implicit in the organisms that are their ontological causes, the nature of changes that occur in evolution has to do with how they fit into the structure of the whole cycle, and we keep that in mind, by recognizing that the causally relevant unit is the whole cycle, rather than just the three dimensional organism.

Since reproductive causation entails all the essential elements of Darwin’s mechanism, it can explain everything currently explained in evolutionary biology. But this ontological derivation of them is not merely proof that there is an ontological necessity about what has already been discovered by empirical science. It is the beginning of a proof of new propositions about the course of evolution, first of all, that evolution is a gradual change in the direction of natural perfection.

Ontological effect: gradual change toward natural perfection. Reproductive causation implies that evolution is progressive. The reason for calling it progressive is that the global regularity constituted by reproductive cycles and space involves change in the direction of natural perfection. That is, as we shall see, how reproductive cycles add up in space over time. But this is also to introduce the foundation for explaining the nature of goodness, which is one of the mortgages that must be paid back in order to use spatiomaterialism as an ontological foundation, and thus, it is appropriate to start by explaining what I mean by “natural perfection” and making clear how it affords an explanation of the nature of goodness.

Natural perfection. A dictionary would tell us that “perfect” refers, in general, to the most complete, whole, or mature state of a thing, that is, a state without defects, a state in which no change would make it superior in any relevant way. Things can be perfect in different ways, but in every case, what makes the perfect stand out is that it is an optimal state that can hold in a certain kind of part-whole relation. And what I mean by “natural perfection” is a certain kind of optimal part-whole that is most appropriate to the basic nature of what exists in a world like ours, where everything is constituted by matter and space enduring through time.

What is perfect is always a whole that is made up of parts in some way. Though there are many different ways that parts can make up whole, the whole must be more than just the sum of its parts. There must be relations among the parts. And to be optimal, its parts must be of the right kinds and numbers and they must be related in the right ways. Thus, in general, a part-whole relation can be said to be optimal when it makes the most out of the least in some salient, determinate way. Though it depends on the kind of part-whole relation involved, perfection is an optimum that comes from combing the fewest and simplest parts of some kind so that the whole makes the most of them in a salient way.

Something can be said to be perfect of its kind, therefore, to the extent that it makes the most of things of its kind in the appropriate way. Beautiful works of art might be said to be perfect of their kind, because, given a suitable, classical definition of beauty, they involve such an optimal part-whole relation. But what I mean by “natural perfection” involves a far more basic part-whole relation, because perfection of its kind is a part-whole relation that makes the most of what exists in a natural world, that is, of the substances that endure through time.

In a spatiomaterial world like ours, perfection would have to make the most of space and matter enduring through time. Though its basic nature is just a form of matter in motion, it is not fair to paint the portrait of the world as a bleak picture of cosmic indifference. To living things, at least, there seems to be a difference between good an bad. And the significance of the law of entropy increase is not, despite its universality, that the fate of the world is a heat death in which everything has the same temperature. Rather, its significance is that there is such a thing as free energy, for that affords a salient way in which the most can be made of the parts in a spatiomaterial world like ours. Though entropy never decreases, the large scale structure of the universe is such that potential energy is constantly becoming evenly distributed heat, and since that means that there is a constant supply of free energy, there is a salient way that the most can be made out of what exists. As we have seen, material structures can use free energy to do work, and if such structural causes were to use as much of the free energy available in the region to do the work of controlling as much as possible what happens in the world, such a world would obviously have an optimal part-whole relation of the kind by which “perfection” is defined.

An optimal part-whole relation is one that makes the most out of the least, and in the case of something that is naturally perfect, the whole does the most in the sense of exercising maximum power, given the available free energy, and it does so with the least in the sense that it uses the fewest and simplest structural causes needed to exercise that power. That is an optimum that is often called “maximum efficiency,” though as we shall see, that does not characterize what is involved in natural perfection adequately.

Maximum efficiency is the kind of optimal part-whole relation that is the goal in designing machines. In the case of automobiles, for example, the goal is maximum power, reliability and efficiency in serving its function (say, safe transportation) at the least cost in parts, effort of construction and energy consumption. And since machines eventually wear out, the goal is a machine in which all the parts wear out at the same time.

Natural perfection involves maximum efficiency, but it is a more basic and, thus, more general kind of optimal part-whole relation, because it also involves doing as much as possible in the way of using free energy to control what happens in the world. The ultimate natural perfection is a optimum in which any relevant change in the parts or their relationships would make the whole less powerful.

Natural perfection is the direction of evolution by reproductive causation, but as we shall see, natural perfection involves several part-whole relations that are optimal in this sense. Two of them characterize the direction of gradual evolutionary change, the natural perfection of organisms and the ecology, as we shall see shortly. But gradual evolution is only one of the global regularities generated by reproductive causation, for there are also revolutionary episodes in evolution. Together, as we shall see, these two global regularities entail change in the direction of a natural perfection with an overall structure on planets (or in planetary systems) like ours.

Goodness. It should be noted at the outset that natural perfection plays a very important role in this ontological argument, because it affords an explanation of the nature of goodness, enabling us to pay back one of the four mortgages we took out in order to use spatiomaterialism as the foundation for proving these necessary truths in the first place (that is, along with an explanation of consciousness, how Einsteinian relativity could be true, and the existence of something worthy of worship).

Goodness can be defined in terms of natural perfection, because perfection is a kind of part-whole relation. Natural perfection is the property of the whole in such optimal part-whole relations, and so goodness can be defined as the property of the parts. That is, goodness can be explained ontologically as the property of contributing to the natural perfection of the whole of which it is part. And since all forms of natural perfection fit together in a necessary way as part of the overall structure of natural perfection, there are no ultimate conflicts about what is good, and goodness is simply the property of contributing to natural perfection.

Every part of the optimal part-whole relation that defines natural perfection is good, but since the perfect whole does the most with the least in the way of parts, each part makes a unique contribution. No part is redundant (though many parts of the same kind may be needed for the whole to be perfect).

By this definition of “good,” therefore, what is good ought to exist, because it is “called for” by natural perfection. That is, if anything that is good did not exist, the whole would not be naturally perfect. There would be a change that would make it more perfect. That is the sense in which natural perfection can be said to "call for" its existence.

Goodness is just a property of parts in relation to natural perfection, but as we shall see, it explains why all the things that are ordinarily considered to be good are good, including goals that are good for beings like us. It even explains an the aspect of goodness that makes such a theory seem impossible, namely, why rational beings ought to choose the good. And it reveals goals to be good that are not generally recognized as such today.

If evolution is progressive in the sense of involving change in the direction of natural perfection, it is also progressive in the sense of making things good (or bad). Progressive evolution is, in other words, the source of goodness in a spatiomaterial world, and since such evolutionary change is inevitable in a spatiomaterial world like ours, the ultimate source of goodness is the nature of the world itself.

The reason for believing that evolution by reproductive causation is progressive is that it is change in the direction of natural perfection, and in the end, there will be at least five different ways in which evolution by reproductive causation makes the world naturally perfect. They all fit together as part of a necessary overall structure, and since there are no basic conflicts to cast doubt on the whole being naturally perfect, it will be clear that the change involved in reproductive global regularities is indeed progressive. The first global regularity caused ontologically by space and reproductive cycles is gradual evolution, and it is change in the direction of the natural perfection of organisms and the natural perfection of the ecology. And gradual evolutionary change is itself a kind of natural perfection. Thus, three forms of natural perfection will be discussed below. Two further forms of natural perfection will be introduced later in this argument (both having to do with stages of evolution).

The natural perfection of organisms is maximum holistic power. The parts of this optimal part-whole relation are the structural causes that are bundled together as an organism going through reproductive cycles. Its power is holistic, because it depends on all the non-reproductive work done by its structural causes and all those parts must be of the right kinds and combined in the right ways. Its power is maximized in the sense that those non-reproductive structural effects control as many of the conditions affecting its reproduction as possible for organisms of its kind. But since free energy is consumed in generating structural effects, power is also maximized when the fewest and simplest structural causes are used because free energy is used most efficiently. Since that is to do the most with the least, maximum holistic power is a form of natural perfection, which will be called the “natural perfection of organisms.”

By the ecology, I mean how organisms exist alongside one another in regions of space. There must be an ecology, because organisms reproduce in space and go through reproductive cycles alongside one another. And there is a natural perfection about the ecology that complements the natural perfection of the organisms, because there is an optimal part-whole relation at the ecological level as well. It is also a kind of maximum holistic power. The parts, in this case, are the organisms going through reproductive cycles, and the whole is a power that depends on all the organisms in the region. Again, the whole is not merely the sum of the parts, because it depends on the kinds of organisms in the region, the numbers of each, and how they interact. In this case, however, holistic power is measured by how much of the free energy available in the region is being used by all of them to fuel their reproductive cycles. Given the kind of perfection that is appropriate in a spatiomaterial world like ours, that is the most salient way of doing the most that can be done. And as we shall see, it is also a case of doing the most with the least, because the organisms that use the free energy are each maximally efficient. I will call it the “natural perfection of the ecology.”

There is even a natural perfection about the process of gradual evolution itself, for there is a way in which evolution also makes the most out of the least when it is due to reproductive causation. In this case, the parts are all the moments in the course of evolution, and the whole is the overall course of evolution itself. Evolution by reproductive causation makes the most out of each moment, because the moments all add up as time passes to change in the direction of the natural perfection of organisms and their ecology. That is, since evolution is progressive, it is itself a form of natural perfection, which will be called the “natural perfection of evolutionary change.”

In order to show that evolution by reproductive causation is progressive, I will show that reproductive cycles add up in space as time passes to a gradual change in the direction of natural perfection. The first step is to see why organisms change gradually in the direction of maximum holistic power, and then why the ecology evolves gradually in the direction of their maximum consumption of the free energy available in the region.

Gradual evolution of the organism. The new derivative ontological cause that has been derived from spatiomaterialism is the reproductive cycle, and reproductive cycles add up in space as time passes by imposing natural selection on themselves. Reproduction is a cause of natural selection, because resources are finite and population growth eventually makes free energy (if not other resources) in any isolated region scarce. Though such scarcity is a change in the environment of each organism, it is not caused by anything external. It is internal, since reproduction is an aspect of reproductive cycles. And since population growth eventually leads to scarcity in a world like ours, some organisms will eventually be unable to survive and reproduce. But as long as there are new, heritable traits within the range of the traits being “tried out” by random variations that would make organisms better able to control the conditions affecting their reproduction, natural selection would tend to favor individuals with new traits that increase their power. Their greater reproductive success would eventually change the population until every member had the new trait (that is, acquired the new power).

If that is how reproductive cycles add up in space as time passes, we can see how evolutionary change would lead to the natural perfection of the organisms going through them. Reproduction would be the main cause of evolution, if these conditions held of organisms that start off simple, uniform and weak and it were possible for new traits to be tried out and bundled together with others in the organism, because evolutionary change of this sort would go on for a long time, adding one new trait after another, making the organisms complex, diverse and powerful. Indeed, it needn’t stop until the organisms are as powerful as possible for organisms of their kind, that is, until there are no more new power-enhancing traits within the range being tried out by random variations on existing organisms. That would be their maximum holistic power, because at that point, no change in the causal connections bundled together in their reproductive cycles that is possible for organisms of their kind would make them any more powerful.

This is to restrict the range of possible traits to those that can be "tried out" by random variations during their gradual evolution, and that depends on the nature of the organism and how random variations are generated (that is, the nature of the structural global regularity). It may be possible to imagine useful traits that fall outside that range, but that would not show that the organisms had a less than maximum holistic power in the relevant sense.

Example of amphibian evolution. To illustrate how reproductive causation could generate such a regularity, consider how it would explain fish evolving into amphibians. Reproduction among fish of various kinds would eventually cause a scarcity in the usable energy and other resources available in the water. Those fishes in which random variations happened to try out traits that enabled them to move their bodies across land, would find plants and other animals that provided a new source of usable energy. Those fish would tend to succeed in reproducing, while otherwise they might have failed.

Something like this apparently occurred among lungfishes about 345 million years ago. These fresh water fish had already evolved lungs, perhaps to absorb oxygen from the air when the water was stagnant and deficient in oxygen, and they had “lobe fins,” or large fleshy bases for their paired pectoral and pelvic fins, making it possible for them to move across land. At first, they were relatively uniform, simple and barely able to complete cycles of reproduction requiring locomotion across land. But reproductive causation would make them increasingly complex, diverse, and powerful. As random variations on their inherited multicellular structure tried out new traits, one new trait after another would be added. Each new trait would make them more powerful at controlling conditions that affected their reproduction, and as their complexity and power increased, new ways of controlling conditions could be tried out by random variations. Thus, fins would gradually evolve into legs, enabling them to crawl more efficiently across land, and since land plants and insects provided many different sources of usable energy, the different ways of acquiring energy would lead to the evolution of different species of amphibians. Amphibians would go on adding one new trait after another, increasing their power, until none of the new traits that could be tried out by random variations on their multicellular structures could make them better able to control conditions that affect their reproduction. Evolutionary change would stop only when they were as powerful as possible for organisms of their kind in whatever environment they occupied.

Such a proliferation of species is called a “radiation,” and it would occur again and again. When a more basic random variation on amphibians finally tried out internal fertilization (instead of fertilization in the water), making it possible for eggs that remained on land to house a form of embryological development that did not involve a larval stage, reptiles would be able to acquire usable energy from new sources on land. Two legged locomotion would be the start that gave dinosaurs their day in the sun. Those with wing-like limbs would begin a radiation of birds.

Long periods of gradual evolution are possible, however, only if the structure of the organism makes it possible for random variations to try out a wide range of new traits. In the animals mentioned above, what makes it possible to accumulate traits in that way is their multicellular structure. Each cell together with its behavior is at least one of the structural causes that is bundled together as parts of a multicellular animal going through a reproductive cycle, and what makes it possible to bundle such parts together is its way of coordinating their behavior as parts of an organism.

Random variations ultimately involve differences in genes, the most elementary structural cause with both essential kinds of structural effects in living objects. But as we shall see, genetic variations make it possible not only for cells to try out specializing in new functions, but also for multicellular organisms to try out new ways of arranging such cells. The latter aspect of random variations is possible because each multicellular animal is constructed by asexual division from a single, fertilized egg cell in a process called “embryological development.”

The kinds of random variations that can be tried out at any point determines the range of new causal connections that are possible at that point. And since they occur randomly, all but a few whose complexity borders on making them impossible would eventually be tried out in a finite period of time. Thus, random variations on existing multicellular structures are, in effect, continually “trying out” new, possible powers, as if they were feeling around for new conditions that it might be useful to control. Whenever a new trait happened to control a new relevant condition (or an old condition in better way), it would tend to be selected. Moreover, as multicellular organisms became more complex, new varieties would be added whenever some were able to tap a new source of energy or an old one in new ways, and each variety would become more powerful in its ecological niche.

The principle of gradual evolution. The example of the evolution of amphibians suggests a basic principle about gradual evolution. If evolution is by reproductive causation, then every power that it is possible for such organisms to evolve will evolve as it becomes possible. This may seem too progressive to be true, but consider the following.

(1) If organisms start out simple and uniform, all possible traits are likely to be tried out, because the range of random variations is not very large. And later on, when organisms are more complex and the range of possible random variations is greater, there will be many more varieties of organisms to try them all out.

This is to assume that a complex variety that acquires a new basic power which makes it better able to tap the usable energy claimed by another will tend to supplant the other. That may require violent storms or other disruptions.

(2) It is not necessary for a random variation to happen on the best way of controlling the relevant condition. Even a weak and unreliable way of controlling some new relevant condition would be selected, and as random variations on it were tried out, that structural cause would be shaped to control it as effectively as possible and to fit it together with other structural causes and their causal connections as harmoniously as possible.

(3) Nor is it plausible to suppose that there are possible powers that just happen not to be tried out, at least, not any basic ones, because organisms are not being forced to make do with whatever random variations are available at the time in order to adapt to externally caused changes in the environment. When the cause of natural selection is reproduction, they have all the time they need for random variations to “feel around” for new powers among alternative ways of controlling relevant conditions and make those traits maximally efficient.

Maximum holistic power. Natural perfection in organisms is maximum holistic power, or the maximum power of the organism to control all the relevant conditions using the fewest and simplest non-reproductive structural effects. That is the optimal part-whole relation in organisms. Let me explain these terms.

Power. What is maximized is power. Power is the capacity of structural causes using free energy to make things happen that would not otherwise happen. The power that is maximized in organisms is the power of its structural causes to do non-reproductive work.

Holistic. The relevant power is holistic, because it is the result of many structural causes working together in some way over the period of the reproductive cycle. Organisms are bundles of structural causes that are reproduced as a whole during the cycle, and each structural cause is responsible for a non-reproductive structural effect, or what is usually called a “trait.” Each such structural cause is a part of the organism that generates a structural global regularity in which free energy is used to make something happen in the world that would not otherwise normally happen, and with many different structural causes bundled together in the organism, their structural effects may occur at any time during the reproductive cycle (including some that occur during the whole cycle, such as the circulation of blood in multicellular animals). Thus, the relevant power of the organism is holistic, because it includes all the non-reproductive work its structural causes do during its whole reproductive cycle.

Relevant. The structural effects that are relevant to the maximum holistic power of the organism are those that control conditions that affect its reproduction. Though it is possible for structural causes to control many kinds of conditions in the world, not all such powers are relevant to the optimal part-whole relation in organisms. Powers are not relevant if they make no difference to whether or not the organism reproduces. In order to contribute to the maximum holistic power of the organism, structural causes must control some relevant condition. (However, this limitation on the powers that are relevant changes, as we shall see, with the evolution of rational animals.)

Maximum. Holistic power is maximum when the organism’s non-reproductive structural effects control as many of the conditions affecting its reproduction that it is possible for it to control.

The powers that are possible are those that are within the range of those tried out by random variations on evolving organisms as they are evolving, including both variations in kinds of structural causes and variations in how they are arranged in the organism (perhaps at several levels of part-whole complexity).

The whole is not just the sum of its parts, because the structural causes depend on one another in various ways to control relevant conditions. The whole is both spatial and temporal, because the structural causes are different parts of the complex material structure that goes through the reproductive cycle (that is, the organism), and they have their structural effects at various times during the cycle. For the power of the whole to be maximum, therefore, the structural causes must be of the right kinds and numbers and they must combined in the right ways. That means that all the relevant conditions must be controlled with the fewest and simplest structural effects, for there is a cost in generating any irreversible structural effect.

When holistic power is maximum, the organism does the most with the least. It is not just the greatest combined power to control relevant conditions, but such a maximum using the fewest and simplest structural causes. Such an optimal part-whole relation is like maximum efficiency, the goal in designing machines. But I will call it “maximum holistic power,” rather than maximum efficiency, because I do not want to suggest that there is some overall function that organisms are serving. The optimum for organisms involves controlling all relevant conditions that can be controlled by organisms of its kind, that is, maximum holistic power to control relevant conditions.

In sum, the natural perfection toward which the gradual evolution of organisms proceeds is their maximum holistic power to control relevant conditions.

Every relevant power evolves as it becomes possible. The powers are the effects of structural causes that are bundled together as the organism going through the reproductive cycle, which are usually identified as traits serving some function. Each kind of structural cause is shaped to make its effect as powerful as possible in controlling some relevant condition. Structural causes are added to the organisms, both new kinds or more of old kinds, as long as they control some new condition affecting reproduction or some old condition more effectively. And the structural causes are shaped so the their effects fit in with the other traits as harmoniously as possible.

Thus, assuming that organisms start out simple, uniform and barely able to complete cycles of reproduction at all, they become more complex, diverse, and powerful. Eventually, all the structural causes that could help control conditions that affect the reproduction of organisms tapping some source of energy will be bundled together harmoniously in a reproductive cycle. Such gradual evolutionary change must stop only when there are no changes within the range of possible random variations that can make them more powerful in controlling relevant conditions. Though this end may be approached asymptotically, evolution will be in the direction of bundles of structural causes whose power, taken together over the whole cycle, is maximum.

Functional explanation. Since the gradual evolution of organisms is in the direction of natural perfection, there is an ontological definition of “functional,” one that entails the validity of functional explanations. This implication of spatiomaterialism solves various philosophical problems about the nature of functions, which are discussed in Epistemological philosophy of causation. But functions must be mentioned here, because I will talk about them and use them to explain what evolves. And though traits of organisms are only one sort of thing that is functional, if evolution is due to reproductive causation, I will discuss how they are functional here, since they are the focus of attention in contemporary biology.

In other words, there are "ends" built into nature, much as the teleological view of nature has long supposed. But change does not occur for the sake of such ends because of final causation, as Aristotle believed. Instead, such changes are inevitable products of evolution. They are consequences of the reproductive cycle as an ontological cause of global regularities.

Functions as descriptions of traits. The functions of traits are the relevant conditions that they control. What is bundled together as an organism going through reproductive cycles are structural causes, and as organisms change gradually in the direction of natural perfection (for organisms of their kind), structural causes come to control conditions that affect their reproduction. Those relevant conditions are the functions served by the traits of the organism.

The function of a non-reproductive structural effect is to control some condition that affects the reproduction of the organism of which it is part, and being functional in that way is what it contributes to the natural perfection of the organism.

Thus, any of the objects, events or conditions that are involved in the structural cause bringing about its non-reproductive structural effect can be said to be functional and to have the function of controlling the relevant condition involved, including all the features of organisms that are identified as its traits. Thus, not only the heart, but also the beating of the heart, is functional, because it is part of the structural effect by which energy is distributed to all parts of the animal body.

To be functional is to be good. Since being functional entails controlling a relevant conditions, it contributes to the natural perfection of the organism, and that is the definition of “good.” Functionality is a form of goodness.

Functions as explanations of traits. Functions are not, however, merely a way of classifying traits by the relevant condition they control, for they are also causes of traits and can be used to explain them. The relevant conditions that must be controlled in order for the organism to be naturally perfect are in the cards, so to speak, because, as we have seen, every possible power inevitably becomes actual as it becomes possible. What it is possible to control depends on the range of structural causes that are tried out as random variations on the evolving organisms, and since those structural causes among them that promote the reproduction of the organism will eventually be naturally selected, the organism will inevitably acquire all possible structural causes that control some relevant condition. Thus, the organism acquires them because they are functional, and the function can be said to be the cause of the evolution of the trait that serves them. The function explains, therefore, the existence of the trait in the organism.

This causal connection seems puzzling, because the traits are also the efficient causes of the conditions they control, which are said to be their functions. The heart causes the circulation of the blood that is said to be its function. But there is a reverse causal connection in which the functions cause their traits. The function of circulating the blood is what causes the heart to evolve. What makes this true is that the former is a case of structural causes generating a structural global regularity, whereas the latter is a case of reproductive causation generating a reproductive global regularity, namely, the global regularity in which all possible powers necessarily become actual.

Since functionality is a form of goodness, it follows that the goodness of the trait can also be said to be what causes it to evolve. Among the possible traits, those that are good are naturally selected because they contribute to the maximum holistic power and, thus, the natural perfection of the organism.

“Survival and reproduction.” Finally, if evolution is by reproductive causation, it is misleading to say that traits "contribute to the organism’s survival and reproduction.” Though it may not be false to say that traits are selected for contributing to the organism’s survival and reproduction, that phrase makes it sound as though traits, and even survival, are merely means to the end of reproduction. But almost the opposite is true, if evolution is a global regularity caused ontologically by the reproductive cycle.

The end for which the traits are means is not reproduction, but controlling relevant conditions. The organism has the traits because they contribute to maximum holistic power in controlling conditions that affect its reproduction. The fact that natural selection is made by success in reproduction means that what is selected is the whole bundle of causal connections, rather than some particular trait. And as we have seen, since natural selection is also caused by reproduction, the bundle is selected for its power to control all the conditions that affect its reproduction over a whole reproductive cycle. Any particular trait is included only because it controls some relevant condition that would not otherwise be controlled.

Non-reproductive structural effects have functions, as we have seen, because they control relevant conditions. The relevant condition they control is their function. Though reproduction is also a structural effect, it has no function. Reproduction is merely the cause of evolutionary change in the direction of natural perfection, including the maximum holistic power of organisms. Thus, reproduction determines which conditions it is relevant to control. But that does not make reproduction the ultimate function of non-reproductive work. Evolution is not change in the direction of reproduction, but in the direction of the maximum holistic power of organisms, or their natural perfection.

In other words, what is good for the organism is not reproduction, but controlling conditions that affect reproduction (though the latter may include some that are more closely related to reproduction, such as a mating or caring from offspring in the case of animals). When the organism controls the relevant conditions, reproduction generally takes care of itself, since it has been part of the reproductive cycle from the beginning.

Gradual evolution of the ecology. Implicit in the gradual evolution of organisms is the gradual evolution of their combination in regions of space, or the ecology. If organisms start off simple, uniform and barely able to complete reproductive cycles, then reproductive causation will make them not only more complex and powerful, but also more diverse. The usable energy in any region of space is not only finite, but takes many different physical forms, such as various kinds of photons, energy-rich molecules, and other organisms. Thus, as these organisms specialize in tapping different sources of energy (or the same sources of energy in different ways), they radiate into all possible ecological niches, and evolutionary change in them—and in whatever other organisms may remain and adapt to them—will be in the direction of their maximum consumption of free energy, which is the natural perfection of the ecology.

At the ecological level, there is a part-whole relation which can be optimal in the way that is appropriate in a spatiomaterial world like ours. The parts are the organisms, or bundles of structural causes going through reproductive cycles, and the whole is not only how the organisms are combined spatially in the region, but also how their reproductive cycles are combined in time over a period that is long enough to include all and any regular changes in the environment, such as seasons. The species of organisms that evolve during any radiation tend to mirror the sources of usable energy in the region. As each species becomes more efficient and approaches the maximum holistic power for organisms of its kind, reproductive causation is also making their combination in the region optimal, but in a different way from the organisms.

The effect of the whole combination of organisms that is being maximized is the consumption of free (or usable) energy to fuel cycles of reproduction. Any unused free energy is an ecological niche to be occupied, if traits being tried out by random variations on any existing organism enable it to tap the energy as fuel for its reproductive cycles, for that overcomes the scarcity due to population growth. Thus, all possible ways of tapping usable energy come to be included in the ecology. And organisms are combined in the most efficient quantities, since the finite amount of usable energy is what stops population growth and causes natural selection in each species. The maximum may be approached only asymptotically, but as reproductive causation maximizes the power of the organisms over their whole reproductive cycle, evolutionary change at the ecological level is in the direction of appropriating more and more the usable energy in the region to fuel reproductive cycles, making the ecology as a whole maximally powerful in the way that is appropriate to a spatiomaterial world like ours.

Evolution by reproductive causation is change in the direction of natural perfection for both the individual organisms and their ecology. Indeed, it is only because the organisms have maximum holistic power that the ecology does the most with the least.

Natural perfection at the level of the ecology is using as much of the available free energy as possible to fuel the reproductive cycles of maximally efficient organisms of many varieties. But it does so by combining the simplest and fewest organisms—simplest because maximum holistic power at the level of individual organisms is using as little usable energy as possible to exert the greatest power to control all the conditions that affect its reproduction, and fewest because there are no more organisms than the supply of usable energy will support. Thus, these two forms of natural perfection are opposite sides of the same optimum: using the most energy to maximum effect. In other words, gradual evolution is change in the direction of a “compound” natural perfection, because the optimum for the ecology is a whole made up of parts that are, themselves, optimal as organisms.

This kind of perfection is rightly called "natural," because it makes the most of the basic nature of what exists in a spatiomaterial world like ours. The only possible way of making the most of space and matter in time is using free energy to control what happens in the world. At the end of gradual evolution, not only does the ecology consume as much of the free energy available to control conditions in the world as possible, but also all the conditions in the world that can be controlled by them are controlled (because the organisms are as powerful as possible for organisms of their kind and they use as little free energy as required for that maximum).

The natural perfection of the ecology has the same implications for organisms that its member the natural perfection of the organism has for its traits. Just as the organism's traits are functional because they control some relevant condition, so organisms in the ecology are functional because they consume some of the available free energy. And since to be functional is to be good, organisms are also good because they consume the free energy in some form or way. That is what the organism is good for, as far as the natural perfection of ecology is concerned.

The analogy among kinds of natural perfection suggest a further step. There is, as I suggested earlier, another kind of natural perfection about gradual evolution, namely, the way in which reproductive causation brings about the natural perfection of the organism and the ecology. Each phase of the process of gradual change in that direction makes a necessary contribution to their existence at the end, and since that is also an optimal part-whole relation, each phase can also be said to have such a function and to be good for contributing to the perfection of the whole in that way.

Finally, if natural selection is caused by reproduction, change in the direction of this compound natural perfection is inevitable, for it does not depend on externally caused changes in the environment. To be sure, evolutionary change itself may be seen as a change in the environment. As organisms become more powerful, traits that random variations have been trying out all along but were neutral or even harmful may suddenly become useful in promoting reproduction because of how they work together with other traits that have been acquired in the meantime. Or traits that first evolved to control one condition may come to control others. And evolutionary change in one species may change the effects of the traits of other species, requiring them to adapt or become extinct. But if such changes in the effects of traits are environmental changes, they are not caused externally. They come from the increasing power of the evolving organisms in whatever environment they all inhabit and, thus, are internal to evolution by reproductive causation, like scarcity due to population growth.

Reproductive causation: Revolutionary evolution. There is another reproductive global regularity, because there is a further way in which reproductive cycles can work together with the space containing them to generate another global regularity. It can occur only when reproductive cycles have already been gradually changing for some time in the direction of natural perfection, but it takes evolution beyond that the limit of optimum. The ontological cause comes from a more radical variation in the organisms that have already evolved, namely, higher levels of part-whole complexity in the structures of the organisms going through reproductive cycles. Since such a random variation begins a new stage of gradual evolution, which can in turn make possible yet another such revolutionary change, it generates is a series of stages of gradual evolution, and thus, this global regularity is “revolutionary evolution.”

It is evident that something more is needed to explain evolution on earth. Though the radiation of increasingly powerful organisms into all possible ecological niches can explain some of the variety among organisms, the basic reproductive global regularity implies that evolution is just one long, incremental change. Though gradualism is what Darwin expected, Darwinists now believe that the organisms found on earth are far too various, if not also too complex, to be explained by a gradual change in the direction of ever greater fitness.

Indeed, there is good evidence against gradual evolution. The fossil record reveals that, time and again, after a long period of little change, new species show up quickly, usually many species at about the same time, only to be followed by another long period of very little change. Called “punctuated equilibrium,” this phenomenon cannot always be explained as a radiation in which organisms of some kind acquire the power to tap a new source of usable energy in the environment. Something besides the addition of one new trait after another is helping determine the overall course of evolution.

Reproductive causation offers, however, a simple and plausible explanation of these phenomena. The further way that space can be combined with reproductive cycles to constitute a global regularity entails stages of gradual evolution. Such stages can explain not only why evolutionary equilibria are punctuated by the appearance of many new species all at once, but also why organisms are so much more varied than would be expected of gradual evolution. Furthermore, the sequence of stages makes evolution change in the direction of a natural perfection that is far grander sense than merely maximizing the holistic power of both organisms and ecology. Let us consider, first, the ontological cause of revolutionary evolution, and then the ontological effect itself.

Ontological cause: levels of part-whole complexity. Though the basic ontological cause is reproductive cycles, they can help generate another reproductive global regularity, because reproductive cycles can combine with space to cause ontologically a new stage of gradual evolution.

What goes through cycles of reproduction are the many structural causes bundled together as the complex material structures that I have been calling “organisms.” That part-whole complexity about each organism is what makes it possible for a gradual evolution to go on for a long period, because that is the source of the wide range of random variations that can be tried out and that can accumulate as the many new traits that make organisms increasingly complex, diverse, and powerful. But that same aspect of the nature of organisms suggests another possibility. Once organisms have approached natural perfection for organisms of their kind, it may be possible for those organisms to serve as various structural causes that are bundled together in a new organism, so that they all go through reproductive cycles as a whole. That is what I will call a “higher level of part-whole complexity” in organisms.

Organisms are complex mechanisms that can fairly be said to behave in various ways, because they are bundles of structural causes whose effects work together to control all possible conditions that affect their reproduction. Such parts are responsible for the non-reproductive structural effects that are called “traits,” but their functions, or the relevant conditions they control, may lie either in the organism (determining its physical properties and how they change) or in the world in which the organism exists (such as acquiring energy from the world and sending offspring into it).

The simplest way that a higher level of part-whole complexity is possible is for such organisms to be bundled together as a complex material structure that goes through reproductive cycles as a whole. Each simpler organism that is included would then be a structural cause with effects that are (or become) functional traits of the higher level organism.

(In this case, it is a higher level of part-whole complexity of primary structures. A "primary structure" is a material structure that can generate an entire reproductive cycle, including both reproductive and non-reproductive work, and since the lower level organism is a primary structure, a higher level of part-whole complexity based on such organisms is a higher level of part-whole complexity in primary structures. I use this simple case to introduce the cause of evolutionary stages, though as we shall see, there are other ways in which higher levels of part-whole complexity can cause additional stages of evolution.)

But in order to go through reproductive cycles as a higher level organism, the structural causes combined in its material structure must work together in the cycle to control conditions that affect its reproduction, and what is more, all the parts must be reproduced in order for the higher level organism to be reproduce. Thus, it is also necessary to coordinate their behavior.

A behavior guidance system is, therefore, required for organisms to be combined as parts of a higher-level organism (that is, an organism with a higher level of part-whole complexity in primary structures). Some such system must be part of the random variation that gives rise to the higher level organism.

I will call it a “biological behavior guidance system.” (This is to distinguish it from another kind of behavior guidance system that will also turn up as part of this global regularity, namely, the animal behavior guidance system, whose function is to guide the behavior of whole organisms in acting on other objects in space.) The function of the biological behavior guidance system is to coordinate the behavior of the lower level organisms (or primary structures) of which it is composed so that it can go through reproductive cycles as a whole. And its physical nature depends on the nature of the organisms (or primary structures) whose behavior is being coordinated.

By coordinating the lower level organisms (or primary structures), the biological behavior guidance system will have structural effects that can control conditions that affect reproduction. But in order to go through reproductive cycles, it must also be able to reproduce the higher level organism as a whole. But this is possible, because its parts are organisms that evolved during the previous stage and (as primary structures), they are already able to reproduce themselves. The reproduction of the higher level organism is simply a matter of coordinating its parts to reproduce as part of the same process. But the capacity to control the reproduction of its parts can also be used by the higher level organism to do non-reproductive work.)

In general, it is already possible to see how a higher level of part-whole complexity would cause a new stage of evolution. Assuming that it is possible for reproductive cycles with such higher level organisms to be tried out as a random variation on organisms that have already evolved, they would have the power of a whole army of the structures of lower level organisms to control conditions that affect its reproduction as a whole. This quantum leap in power would enable them to begin a new stage of evolution.

Since they would come to exist at first from a radical random variation, the higher level organisms would start off simple, uniform and weak. But assuming that they go through reproductive cycles, reproductive causation would shape them to control conditions affecting reproduction that were simply beyond the reach of lower level organisms acting separately. That is, as random variations in the kinds, numbers, and arrangement of the lower level organisms (including how their behavior is coordinated) were tried out, the scarcity due to their own population growth would impose a natural selection on them, and the higher level organism would become more complex, diverse and powerful. There would be enough new powers to be acquired for an entire stage of gradual evolution, because the potentially functional traits of a higher level organism are caused by the kinds, numbers and arrangements of its lower level parts. Thus, organisms would change gradually in the direction of natural perfection for organisms of their kind.

As they approach natural perfection for organisms of their kind, however, another such radical random variation may be possible. Its yet higher level of part-whole complexity would begin another stage of gradual evolution. Thus, as one stage followed another, evolution would be an overall change in the direction of what might be called the “natural perfection of life,” in which increased power comes from higher levels of part-whole complexity.

The spatial derivation of the ontological cause. Higher levels of part-whole complexity in the structures of the organisms going through reproductive cycles are, therefore, the ontological cause of the revolutionary episodes in evolution that being new stages of evolution. Though, as we shall see, such stages of evolution follow one another in such a way that evolution is change in the direction of a grander form of natural perfection, higher levels of part-whole complexity are just a complication of the ontological cause that is already at work in causing gradual change in the direction of natural perfection, the basic reproductive global regularity. Evolutionary change is still just how the wholeness of space makes reproductive cycles add up as time passes. But in causing revolutionary change, space works together with reproductive cycles in a further way, because the structure of space within the region is what makes it possible for the structures of organisms from one evolutionary stage to be bundled together as the various structural causes making up a higher level organism.

The relevant part-whole relation is a kind of spatial relation, and it is because the structures of the the lower level organisms coincide with space that it is possible for them to be combined as the several parts of a higher level organism. This role of space as an ontological cause resembles the role it played in causing structural global regularities, for the structure of space is what made it possible for simpler material objects to be combined as composite objects with geometrical structures and for such material structures to move around in space. And the new (derivative) ontological cause also comes from a new kind of unity, the way in which the structures of lower level organisms are combined as parts of a single higher level structure (just as material structures came from a new kind of unity of material substances that gave them an unchanging geometrical structure as a whole).

Though the part-whole relation in space is also what makes higher level organisms possible, organisms are not just material objects. They must reproduce as well as do various kinds of non-reproductive work in order to go through reproductive cycles. Thus, combining simpler organisms as parts of a higher level organism cannot usually be accomplished by simply attaching them to one another. They need a biological behavior guidance system to coordinate the behavior of their parts.

What makes reproductive cycles a different kind of ontological cause from the complex material structures that go through them is their temporal structure. That is, the new kind of unity behind the ontological cause of reproductive global regularities is the temporal unity of the cycle of reproduction. The way that time is part of the nature of the ontological cause is what makes reproductive global regularities so dramatically different from structural global regularities.

It is, however, space that makes revolutionary evolution so different from gradual evolution. Space together with the structures of lower level organisms constitute the higher level organism, and since space has a structure that allows higher level organisms to go through reproductive cycles, the wholeness of space plays its familiar role, making reproductive cycles add up over time so that the scarcity caused by their multiplication imposes natural selection them and organisms evolve gradually toward natural perfection for organisms of their kind (and help make the ecology naturally perfect in the process).

Since wholes in part-whole relations can be parts of more inclusive wholes, there can be a series of part-whole relations in the structures of material objects. Keeping track of them is what will enable us to trace the stages of gradual evolution that occur in its overall course. Since the notion of “a series of levels of part-whole complexity” is so central to this argument, it is worth the risk of belaboring the point to be clear about what is meant by it.

To illustrate what I mean, consider a box containing many similar cartons each filled with objects of some kind. Both the box and the cartons are wholes made up of parts, but the parts in the box are themselves wholes, namely, cartons, each containing many parts of some kind. It is even clearer how levels of part-whole complexity can form a series, each nested inside the next, when there are more than two levels of part-whole relations. Each of the cartons contained in the box may contain objects that are themselves containers of many similar objects (such as packs of cigarettes). Or going in the direction of the larger, the boxes of cartons of packs of cigarettes may be loaded together in a semi-truck’s shipping container which, in turn, is contained within a ship’s hull. There is, in principle, no limit to the number of levels of part-whole relations in a series. (In the decimal representations of numbers, for example, each decimal place represents a whole that is made up of ten “parts” in the decimal place to its right, and there is no limit to the number of decimal places in numbers.)

However, the “wholes” that are relevant to reproducing organisms are not just spatial structures made up of spatial parts, but rather spatiotemporal wholes made up of parts generating structural effects, that is, cycles of structural effects. Thus, a better, though still rough, model for a series of levels of part-whole complexity would be the levels of government into which individuals are organized in the United States: local, state and federal. Taking individuals to be the parts in which the simplest structural effects, local government can be seen as wholes that are then parts of state governments, which are wholes that are, in turn, parts of the federal government. There are three levels at which structural effects are bundled together as wholes that are, in turn, bundled together as (complex) structural effects on a higher level of government.

Kinds of levels of part-whole complexity. When a series of levels of part-whole complexity is found in a single organism, there is a determinate order to the material structures involved. And since reproductive causation works from simpler to more complex organisms, the stages of evolution by which the levels of organization accumulate have a determinate temporal order. But the actual series of levels of part-whole complexity that determines the overall course of evolution are of two or three different kinds, and each kind of part-whole complexity involves a different series of levels.

The basic and most obvious series is the series of “levels of biological organization.” They are the kind of part-whole complexity that has been mentioned thus far in describing the ontological cause of revolutionary evolution, in which lower level organisms are bundled together as parts of a higher level organism to go through reproductive cycles as a whole. (Since the material structures of independent organisms are primary structures, which can generate all the structural effects required to complete an entire reproductive cycle, including both reproductive and non-reproductive work, these are levels of part-whole complexity in primary structures.)

Multicellular organisms are the best example of them. Indeed, they are named after the level of part-whole complexity that is obvious in them (being composed of many cells). But it is only one in a series of levels of biological organization.

It should not be surprising that there is at least one more level of part-whole complexity in primary structures in the direction of the small from multicellular organisms, because each of the cells is itself a whole composed of parts that are also primary structures. The behavior of each cell is known to be determined somehow by many genes, and genes do both reproductive and non-reproductive work There is however, as we shall see, an additional level of part-whole complexity between cells and genes (and genes themselves have the part-whole structure required to be complex material structures of the kind required for reproductive causation).

Moreover, there is a level of biological organization above multicellular organisms, for example in insect colonies and, in a unique way as we shall see, in human society, yielding five distinct levels of part-whole complexity in primary structures altogether.

Within the structure of multicellular animals, however, there is another series of levels of part-whole complexity. It occurs in the nervous system. “Levels of neurological organization,” as I will call them, are capable of causing stages of evolution, because the nervous system is the system for guiding the behavior of multicellular animals, that is, its “animal behavior guidance system.”

The nervous system is composed mainly of neurons, and since neurons are cells, they can also be organized at a series of level of neurological organization. Not only individual neurons, but whole systems of neurons can be multiplied in number and fit together as parts of a super-system of neurons at the next level. But they are not levels of part-whole complexity in primary structures, because systems of neurons are not able to reproduce on their own. They are levels of part-whole complexity in a structure set up by the animal's primary structure.

Since each higher level of neurological organization can open up an entire range of powers that were previously out of reach, the evolution of a higher level can begin a whole new stage of evolution. Then, as it approaches natural perfection for organisms with its level of neurological organization, yet another level can be tried out, and thus, the series of neurological levels can cause a series of stages in the evolution of multicellular animals.

Let me emphasize that, since the nervous system is an organ set up by the biological behavior guidance system of multicellular animals, the stages caused by levels of neurological organization are quite different from stages caused by levels of biological organization. Neurological levels do not require a new biological behavior guidance system to coordinate the behavior of the lower level organisms, because the parts are neurons or systems of neurons and their behavior is already coordinated by the multicellular biological behavior guidance system. That is what enables them to guide the behavior of the animal.

Though there are as many as seven levels of neurological organization, the last three also depend on a higher level of part-whole complexity in the biological series as well. The level of biological organization above multicellular animals will be called the “social” level, and as we shall see, when the nervous system is used as a biological behavior guidance system to coordinate the behavior of the multicellular animals, what evolves are a kind of organism that will be called a “spiritual animal.”

Three of the levels of neurological organization occur only in spiritual animals, and thus, there is an important difference between two parts of that series of levels, the levels of neurological organization in multicellular animal behavior guidance systems and the levels of neurological organization in spiritual animal behavior guidance systems.

In order to keep these levels of organization straight and to provide a map of the overall course of evolution, all the relevant levels of part-whole complexity are catalogued here. And before tracing the individual stages, I will look ahead to what spatiomaterialism implies about the evolutionary stages involve in each series of levels of organization.

Levels of biological organization. The levels of biological organization involve a series of levels of part-whole complexity of the basic kind sketched above, that is, levels of part-whole complexity in primary structures. In each case, the organisms that evolve at one stage of evolution are the structural causes that are bundled together as a higher level organism that begins the next stage, and what evolves at the higher level is a mechanism that coordinates their behavior, including their reproduction.

Proto-organismic level: RNA molecules. The “organisms” on the lowest level of biological organization are RNA molecules. The structural causes bundled together in them are (or at least include) the triplets of four different kinds of nucleotides that have become the so-called genetic code. Such parts are organized (bonded by a sugar and phosphate backbone) as an RNA molecule, and that chain of links is all that “coordinates” the behavior of these simplest organisms to generate both the reproductive and non-reproductive work that is required to go through reproductive cycles.

The RNA molecule can reproduce as a whole by a two stage process in which each nucleotide attracts a complementary nucleotide so that the complements become bound as parts of a second RNA molecule, and then the same process occurring in the second RNA molecules results in an RNA molecule like the original.

The distinctive structural global regularity that each such unit of the genetic code generates (that is, its non-reproductive work) is to help prescribe which kind of amino acid would be added to the protein molecule being synthesized (by a peptide bond linking them all in a chain of amino acids).

Though RNA molecules satisfy our definition of the kind of material structure that goes through reproductive cycles, that is, a primary structure, it is something of a stretch to think of them as organisms. But as we shall see, there is indeed a way, in a spatiomaterial world like ours, in which RNA molecules would inevitably go through regular cycles in which they generate both kinds of structural global regularities (reproduction and the non-reproductive work of directing the synthesis of proteins). They start out simple, uniform and weak, but gradual evolution by reproductive causation would make them complex, diverse and powerful. The most important power that would evolve during the first stage would be a reliable and efficient way of synthesizing protein molecules (the molecular machines by which traits in all living organisms are generated).

Prokaryotic level: DNA molecules. The minimal organisms at the second level of biological organization are DNA molecules. The structural causes bundled together in them as a higher level “organism” are the organisms (or primary structures) from the lower level, and once again, being linked together as parts of the same macromolecule is all that coordinates their behavior at first. Instead of being made up of RNA molecules, DNA molecules are made up of variants on them, called genes (with a substitution for one of the four kinds of nucleotides used in RNA and a slightly different sugar and phosphate backbone). Each DNA molecule is actually two strands of complementary nucleotides that are most stable when attached to one another, forming the now famous “double helix” structure. But they have both kinds of structural effects that are essential to primary structures, reproduction and non-reproductive work of various kinds.

DNA molecules can reproduce as a whole in much the same way as RNA molecules (though the two complementary strands must unzip and reproduction requires the assistance of a certain protein molecule).

The structural causes bundled together in them are called “genes,” and each gene does its non-reproductive work in much the same way as the RNA molecule as a whole. But since the RNA structures are contained as segments of a DNA molecule, each segment must first be transcribed as a messenger-RNA molecule (mRNA) and only then can it use the highly reliable process inherited from the first stage of evolution (requiring the use of ribosomes and transfer-RNA) to synthesize a certain kind of protein.

Though at first the behavior of these RNA level organisms is coordinated merely by being parts of a single DNA molecule, new mechanisms of coordination are added with the evolution of proteins that are able to repress, promote and de-repress the transcription of specific mRNA from specific segments. As products of a radical random variation, DNA molecules would have to start out simple, uniform and weak. But since there is, as we shall see, a way in which DNA molecules would inevitably go through entire reproductive cycles, their population growth would eventually make resources scarce and natural selection would be imposed. As they became complex, diverse and powerful, DNA molecules would eventually surround themselves by cell walls, controlling the behavior of their lower level organisms more completely, and eventually, as we shall see, there would come a point at which it would be obvious that life had begun. Extant remnants of this stage are prokaryotic cells, such as bacteria, cyanobacteria and archeabacteria.

Eukaryotic level: the nucleus. The minimal organisms at the third level of biological organization are cells with a nucleus, for the structural causes that are bundled together in them are organisms from the next lower level or their equivalent (that is, DNA level primary structures). Indeed, lower level organisms are bundled together in two ways, first, as multiple chromosomes in the nucleus, and second, in most kinds of nucleated cells, as organelles in their cytoplasm, either both mitochondria and chloroplasts (in plant-like cells) or just mitochondria (in animal-like cells). Though the organelles are basically just stripped down prokaryotic cells whose behavior is controlled by the eukaryotic cell, the nucleus is a new mechanism for coordinating the behavior of the DNA molecules in chromosomes (that is, a new biological behavior guidance system), and it generates both kinds of behavior that are essential for a reproductive cycle.

Mitochondria and chloroplasts reproduce themselves in the cytoplasm, but the chromosomes are reproduced in an elaborate process including the entire nucleus, though in both cases it basically is just a form of DNA reproduction from the previous level. We will consider how such a complex mechanism as the nucleus could evolve from prokaryotes.

The nucleus is a mechanism for coordinating the expression of genes on a number of different chromosomes at once, and thus, the cell does non-reproductive work by marshaling an army of non-reproductive structural effects of many lower level organisms (each transcribing various mRNA molecules which then guide the synthesis of proteins). And under the direction of the cell, the self-reproducing organelles generate non-reproductive secondary effects in the same way as prokaryotes.

Since eukaryotes come to exist as a radical random variation on prokaryotes late in their stage of gradual evolution, eukaryotes start out simple, uniform and weak. But as they impose natural selection on themselves by their own reproduction, they become complex, diverse and powerful. Perhaps the most significant contribution to subsequent evolution is the evolution of a process of sexually mixing chromosomes during reproduction. The speed of evolutionary change is accelerated by routinely shuffling lower level primary structures, if only because that makes it possible to combine in a single organism new powers for controlling relevant conditions that were acquired by different organisms in previous generations. But the evolution of sexual reproduction also makes the death of individual organisms inevitable.

Multicellular level: the mechanism of embryological development. The organisms at the next level of biological organization are so obviously made up of organisms from the previous level that it has given them their name. No one doubts that multicellular organisms evolved from single-celled eukaryotes, called “protists,” though multicellular organization is basically different in plants and animals and it evolved many times in plants.

Reproduction in this case usually comes, however, not from all the parts reproducing as parts of the whole (though such asexual reproduction is possible in multicellular plants and many simpler multicellular animals), but by sexual reproduction of egg cells followed by their asexual reproduction. The behavior of the daughter cells can be coordinated by their exchanging messenger molecules (hormones), though in animals, it also involves a mechanism of embryological development that determines daughter cells so that they also move around relative to one another in order to set up the structure of the animal body.

Multicellular organisms do the non-reproductive work of controlling relevant conditions by coordinating the non-reproductive structural effects of its member cells. Such coordination also depends on the exchange of messenger molecules, though in multicellular animals, there is a special organ of cells, the nervous system, for coordinating the cells involved in generating behavior directed at other objects in space.

Originating as radical random variations, multicellular organisms start off simple, uniform and weak, and we have seen how gradual evolution would make them complex, diverse and powerful. The most spectacular product at this level of biological organization is animals with all of the levels of neurological organization mentioned below, for that makes a new kind of animal possible at the social level of biological organization.

Social organisms: language. The most obvious way in which there is a higher level of part-whole complexity than multicellular organisms in the biological series are insect colonies. But there are other examples of colonial animals, such as hydrozoa and blind mole rats, not to mention plants, such as aspen trees, in which whole groves reproduce like multicellular plants. Insect colonies are, as we shall see, an anomalous kind of animal, because they use the same mechanism to coordinate the behavior of multicellular animals as parts of a social level organism that multicellular animals use to coordinate their cells.

That is, insect colonies reproduce as a whole, with a queen having offspring that population the whole colony, and the behavior of different members of the colony is controlled by the exchange messenger molecules called “pheromones.”

But colonial animals are not the only kinds of organisms on the “social” level of biological organization. Another and more distinctive example is human society, and its way of coordinating multicellular animals is language, which depends on the prior evolution of all the levels of neurological organization. The spiritual animal is, as we shall see, a unique level of organization. Among other things, the same, language-based behavior guidance system is both a social level biological behavior guidance system and the new kind of animal behavior guidance system that is made possible by the social level of biological organization.

Levels of neurological organization. The other way that multicellular animals lead to a further series of evolutionary stages is less radical, because it does not involve levels of part-whole complexity in primary structures, that is, in complex material structures that reproduce themselves like organisms. Instead, the structural causes that are bundled together as material structures at a series of levels of part-whole complexity occur within the structure of a single organ of multicellular animals, the nervous system, whose function is to guide animal behavior. The elementary structural causes in this case are neurons, and they behave by “firing” (that is, sending an action potential along its long axon to other neurons affecting whether they fire). The higher levels of part-whole complexity are mechanisms made of many neurons, mechanisms made of many such mechanism, etc.

The levels of neurological organization are basically different from levels of biological organization, because it is not necessary for the new level of organization to coordinate the behavior of its own parts, and certainly not to coordinate their reproduction. That would be required, if it were a biological behavior guidance system. But in this case, the higher level structures is an animal behavior guidance system. What coordinates the behavior of neurons in setting up the nervous system is the mechanism of embryological development, and though neurons do reproduce in that process, the higher level neuronal structures do not. Since the structure of the nervous system is provided for it, the animal behavior guidance system can use that structure as an ontological cause, that is, as a machine, to guide the behavior of the whole animal in acting on other objects in space.

Behavior guidance depends on another kind of behavior distinctive of neurons, namely, “firing” (that is, sending an action potential along its long axon to other neurons affecting whether they fire). Neurons are organized into higher levels of part-whole complexity when the firings of certain neurons in entire groups affects the firings of other groups of neurons, or systems of such groups affect other such systems, etc.

It is not necessary for the relevant material structures at each level of neurological organization to go through reproductive cycles on their own in order to become naturally perfect in the sense of doing the most with the least like perfectly efficient machines, because their gradual evolution in the direction of maximum holistic power is the effect of reproductive causation on the multicellular animals of which they are part.

Whatever their level of neurological organization, such material structures serve specific functions in guiding animal behavior and, at each level of neurological organization, the material structures are shaped to be as powerful as possible in controlling some relevant condition with the fewest and simplest neurons. If, therefore, a series of levels of part-whole complexity were possible in the nervous system, it would generate another series of evolutionary stages during the stage at which multicellular organisms evolve.

The series of levels of neurological organization are divided into two distinct series, because after a certain point in the evolution of the brain, higher levels of neurological organization depend on a higher level of biological organization as well, that is, the evolution of a new kind of animal at the social level. I will, therefore, list the two series of levels of neurological organization separately.

Animal levels of neurological organization. The first series of evolutionary stages caused by levels of neurological organization occurs in multicellular animals whose evolution depends only on natural selection at the level of individual animals.

Somatosensory animals. Somatosensory animals are the simplest multicellular animals, including hydra and sea stars, which interact with other object in space only by contact. In the, single neurons (and their firings) serve the three basic subfunctions in guiding animal behavior: (1) registering sensory input, (2) selecting how to behave, and (3) generating motor output. Such nervous systems are not centralized.

Telesensory animals. Telesensory animals are the simplest animals that can sense objects at a distance from their bodies, and in them, systems of neurons (at least ganglia or two dimensional arrays of neurons in the neural tubes of vertebrates ) serve the three basic subfunctions in guiding animal behavior. The eye’s retina, for example, requires many neurons working together to generate an image of objects at a distance, and locomotion in relation to a distant object requires a system of many neurons to send motor commands simultaneously to all parts of the body. Such centralized nervous systems are found in all the vertebrates mentioned above, from fish to birds, as well as most kinds of invertebrate animals, such as worms, mollusks, insects. “Telesensory animals,” as I will call them, see the whole world around them as the object on which their behavior might act.

Subjective animals. Subjective animals are animals with spatial imagination, namely, mammals. In them complete circuits of systems of neurons serve each of the basic subfunctions in guiding animal behavior (registering sensory input, selecting how to behave, and generating behavior). The distinctive mammalian neocortex marks the shift of behavior guidance responsibilities from the midbrain and hindbrain to nervous mechanisms in the vertebrate forebrain, and as we shall see, by using one circuit of systems of neurons to register sensory input (as the “local image”) and another such circuit to generate bodily behavior, including locomotion (as the “body image”), mammals have evolved a faculty of spatial imagination that enables them to think coherently about how locomotion (and motion) affect the relations of objects in space.

Motor commands can be generated in the “body image” with their effects on the actual body suspended. Such “covert locomotion” calls up memory images of what was previously perceived in the same situations in the “local image,” and so the mammal is able to imagine how certain kinds of locomotion would change the spatial relations of objects in space before acting overtly.

Spatial imagination makes both their own body and other objects in space appear to them as a natural world, and thus, such animals will be called “subjective animals.” Since they have a conception of space, they see the object as located in space and they can understand the effects of motion on spatial relations.

Manipulative animals. The best, if not only, example of manipulative animals are higher primates. A yet higher level of part-whole complexity in neural mechanisms gives them a faculty of structural imagination for thinking about the geometrical structures of objects in space and how they change as a result of manipulation. In addition to the interaction of the “body image” and “local image” circuits that gives mammals generally spatial imagination, each hand must have a comparable system in which a “hand image” interacts with an “object image” to represent the effects of manipulation on the object. Structural imagination is contained within spatial imagination so that the object being handled is seen as located in the subjective animal’s conception of space. With four hands and a body, there are five sets of interacting circuits in the primate brains, giving what I will call “manipulative animals” a yet higher level of neurological organization than subjective animals. They see the object in space as having a geometrical structure.

Spiritual levels of neurological organization. The series of levels of neurological organization in multicellular animals continues in animals that become parts “spiritual animals.” Multicellular animals are the lower level organisms that get bundled together as parts of a higher level organism that goes through reproductive cycles as a whole, on the social level of biological organization. But spiritual animals are radically different from insect colonies, the other social level animals mentioned above, because instead of using the mechanism of embryological development (the biological behavior guidance system from the multicellular level) to coordinate the behavior of the constituent multicellular level organisms, the spiritual animal uses a basically new mechanism, namely, language. The use of language serves both as a biological behavior guidance system (coordinating the behavior of lower level organisms as parts of a higher level organism that goes through reproductive cycles as a whole) and as an animal behavior guidance system (guiding its behavior like an animal at the social level of biological organization). That makes this social level animal unique, and since it has no body except the independently moving bodies of its biological parts, it is aptly called a “spiritual animal.”

The use of language requires, however, a level of neurological organization higher than that of primates. Because of that function, the levels of neurological organization are evident in levels of part-whole complexity in the structures of the linguistic representations they use to coordinate behavior.

Primitive spiritual animals. Linguistic representations at the level of “natural sentences,” with a simple subject-predicate grammar, make it possible to coordinate behavior in nomadic groups of primates, called “hominids.”

A higher level of neurological organization is required for the capacity to generate and understand natural sentences, because not only must covert manipulative behavior be able to combine multiple object images as representations of states of objects in space, but the animal must also be able to generate (and understand) verbal behavior that indicates the kinds of covert behavior involved in constructing the natural representation. That is, linguistic behavior has both a verbal and a nonverbal side.

Such a brain mechanism can serve as a spiritual behavior guidance system, because when a leader assigns different tasks to different members in a public process, not only does each member know what he is supposed to do in a plan of group action, but all the members know what everyone is supposed to do. The same plan of group action is then contained in each of the brains of the members. That is how their behavior can be coordinated in attaining a single goal.

The spiritual animal has both kinds of structural effects required to go through reproductive cycles as a whole on the social level.

The spiritual animal behaves like a manipulative animal at the social level, that is, with each member acting like a distinct hand in concert with the others as part of a common plan for acting on objects in space.

But such spiritual animals can also reproduce as a whole, because the members can all reproduce sexually at the individual level and, when its population becomes too large, the nomadic band can divide into groups that go different ways.

Thus, spiritual animals multiply in space, make resources scarce, and thereby impose natural selection on themselves, so that they evolve by reproductive causation toward natural perfection of organisms of their kind.

Rational spiritual animals. Linguistic representations at the level of “psychological sentences” make subjective animals reflective, and that gives spiritual animals and their members the power of reason.

Psychological sentences take words referring to subjective animals (or spiritual animals) as their grammatical subjects and predicate of them verbs of propositional attitude, such as “perceive,” “believe,” “desire,” and “intend,” followed by a sentence indicating the proposition to which the attitude is taken. Psychological sentences are able to represent the causes of behavior (and beliefs) in subjective animals, and the use psychological sentence makes linguistic animals reflective, because it enables them to use the functioning of their own brains to imagine the behavior guidance processes going on in other brains. They are eventually able to use psychological sentences to represent the causes of their own behavior (and beliefs) as causes in the very process of causing that behavior (or belief), and since that affords a new, reflective level of control over brain processes and the behavior it generates, the causes come to be called “reasons.” Thus, the use of psychological sentences eventually leads to reason.

At this level of linguistic (that is, neurological) organization, not only is language used by a leader to assign tasks, but the linguistic representations exchanged among members of the spiritual animal have the structure of arguments, that is, conclusions about what to do (or believe) together with a reason for them. Thus, in addition to making both the individual and the spiritual animal more powerful, the use of psychological sentences is the foundation for a new form of evolution by reproductive causation to take place, namely, cultural evolution.

In this case, the “organisms” are arguments (with the component sentences serving as the structural causes bundled together in them). The non-reproductive structural effect of argument is to guide behavior (or beliefs). Arguments reproduce when one member convinces another to accept it. Arguments impose natural selection on themselves because the brains into which they can reproduce are finite. And which arguments succeed in reproducing is not just chance, because individuals can judge which among competing arguments is most coherent, given everything they know. Hence, arguments are subject to rational selection and tend to evolve.

Thus, at the rational spiritual level of neurological organization, there is an evolution of the arguments accumulated as the cultures of spiritual animals, and as we shall see, it is change in the direction of natural perfection for arguments (or reason). Arguments have maximum holistic power for “organisms” of their kind when they discover the true and the good.

Philosophical spiritual animals. Linguistic representations at the level of philosophical arguments lead to a step-like increase in the power of reason to discover the true and the good. Philosophical arguments are a higher level of part-whole complexity in linguistic representations, because philosophy uses a foundation to defend more fundamental truths about the world. In one way or another, philosophical arguments try to explain why the other arguments that have accumulated in the culture of rational spiritual animals are valid, ands that gives philosophy a higher level of forensic organization.

There are, as we have seen, two, basically different ways of making such a higher level argument, epistemological philosophy and ontological philosophy. Epistemological philosophy uses a theory about the nature of reason that comes from reflecting on how rational beings like us know to prove that certain ordinary conclusions about the true and the good are correct (or false). Ontological philosophy uses an empirically justified ontological explanation of the world as its foundation for explaining the validity of the ordinary arguments of the rational spiritual level. (Though that leads to an explanation of the nature of reason, its explanation of the nature of reason is not the foundation of ontological philosophy, but just one of its implications.)

The simplest and most natural way to construct such a higher level argument is the ontological approach, but it cannot succeed until natural science has evolved. Thus, the first approach to philosophy to prosper for long is the epistemological approach, and though it inevitably fails on its own (mainly because of how realism leads to ontological dualism and dualism leads skepticism), it gives rise to natural science, eventually making it possible for ontological philosophy to succeed.

There are, therefore, two phases in the evolution of philosophical spiritual animals. They do not reach the maximum holistic power for “organisms” of their kind until ontological philosophy succeeds in making the fullest use of this level of neurological organization.

Though philosophical arguments do not require any change in the brain structures set up by the mechanism of embryological development, they do involve the acquisition of a higher level of neurological organization in the individual brain. But it comes from process of learning language and the arguments that have been accumulated as culture.

However, there is yet another kind of series of stages in the evolution of spiritual animal, because there are levels of part-whole complexity in the social structures (as opposed to cultural structures) of spiritual animals. Among them there is, in addition to cultural evolution, another form of reproductive causation at work on “organisms” constituted by evolved structures (including the evolution of class structure and eventually capitalism, which is a third form of reproductive causation that takes place on the social level). The combination of these various stages of evolution entail a philosophy of history in the 19th Century style. But I will leave those evolutionary stages and their complications for the next section, when we trace the course of evolution through all of its stages in detail, from its beginning through the history that still lies in the future.

Ontological effect: Stages of evolution. Levels of part-whole complexity in evolving organisms, described in the previous section are the ontological cause of another reproductive global regularity, namely, stages of evolution. It is a regularity that shows up over longer periods of time than the first, because it is a series of stages, each of which is the gradual change of organisms of some kind in the direction of their natural perfection (and the natural perfection of the ecology they help make up).

At each stage, some kind of organism starts off simple, uniform and weak and gradually becomes increasingly complex, diverse, and powerful. But evolution does not stop when they attain the natural perfection for organisms of their kind, if it is possible for those organisms (or important structures within them) to become, in turn, multiple structural causes bundled together in an organism with a higher level of organization that goes through reproductive cycles as a whole. If such a radical random variation is possible, it will eventually be tried out, and such higher-level organisms will also impose natural selection on themselves by their own reproduction. That will start another long stage of gradual evolution, because the part-whole complexity in their structures would make it possible to try out and accumulate a very wide range of traits.

Since one stage leads to another, the overall course of evolution is a ratchet-like series of stages of gradual change, each punctuated by a more radical, revolutionary change that begins a new stage of gradual change by trying out organisms with a higher level of part-whole complexity. The way that higher levels depend on the prior evolution of lower levels means that such evolutionary stages can occur only in a certain order, from simpler to more complex, working its way up the levels of organization. That gives evolution an overall direction that could well lead up to beings like us and, perhaps, beyond.

Reproductive causation can explain, therefore, punctuated equilibria and the enormous variety of organisms. Though reproductive causation implies that the gradual evolution at each stage leads to an evolutionary equilibrium, it also explains why such equilibria are punctuated. The punctuations occur when the natural perfection of organisms on one level of part-whole complexity makes it possible for random variations to try out organisms with a higher level of part-whole complexity (either higher levels of primary structures or higher levels of important structures set up by them, such as in the nervous system). And since their higher level of organization enables them to try out a wide range of new traits as random variations that can be accumulated and fit together harmoniously for controlling the conditions that affect their reproduction, a new stage of gradual evolution would begin, leading to another evolutionary equilibrium.

Moreover, if new stages of evolution can be explained by the higher levels of part-whole complexity in evolving organisms mentioned above, reproductive causation can also explain the variety and complexity of existing organisms. In addition to the many varieties of organisms that come to exist at each stage as they divide up the various sources of free energy and become more diverse, it implies that there are differences among organisms that come from their level of part-whole complexity, with each level initiating a radiation of kinds filling all the available ecological niches.

Since this explanation of evolution follows from our ontological foundation, however, its implications about evolution are ontologically necessary truths. They hold in any spatiomaterial world like ours (that is, where matter has a nature that explains ontologically the basic laws of physics and the universe has a large scale structure with planetary systems). Reproductive global regularities are among those necessary truths, including revolutionary episodes in evolution and the evolutionary stages they involve. The ontological cause of revolutionary evolution has been described: each new stage is the evolution of organisms with a higher level of part-whole complexity. But in order to prove that this more complex aspect of the basic reproductive global regularity is a necessary truth, the ontological cause must be shown to entail the effect. That is, it must be shown that each new stage is inevitable, given the previous stage. That is what is done in each of the ten following sections. But the arguments will all be of the same kind. In each case, the inevitability of the next stage of evolution is proved by showing that the relevant higher level of part-whole complexity is both possible and functional.

Possibility of higher level of part-whole complexity. In order to show that a stage of evolution is inevitable, it must be shown that it is possible for organisms with a higher level of part-whole complexity to go through reproductive cycles as a random variation on the organisms that have already evolved. What is possible depends on what already exists, which, except for the first stage of evolution, includes whatever is provided by the natural perfection of organisms and ecology at the previous stage. Thus, the first task at each stage is to show how the outcome of the previous stage of gradual evolution makes possible the radical variation that bundles the lower level organisms together as a higher level organism. It must do so in a way that explains how the higher level structure can coordinate the behavior of the lower level organisms to generate both essential kinds of structural effects, reproduction and non-reproductive work, in one cycle after another. It is not always obvious how that is possible, especially at the first two three stages of evolution and in the case of the evolution of spiritual animals.

Function of higher level of part-whole complexity. Another stage of evolution would not follow, however, even if organisms with the higher level of part-whole complexity can be "tried out" in this sense, unless the higher level enables the organisms to control new conditions that affect reproduction. In order to evolve by reproductive causation, they must be able to control conditions that are beyond the reach of organisms at the lower level of part-whole complexity, or else they will not be able to compete with existing organisms. Indeed, there must be an entire range of powers that they alone can evolve in order for them to go through a stage of gradual evolution and become naturally perfect of their kind. The source of the increased power may be obvious in the earliest and latest stages, but it is less obvious in the case of the levels of neurological organization which fall in the middle.

In order to show that all the stages are inevitable, however, it will not be enough to show that each stage is inevitable, given the natural perfection of organisms during the previous stage. It will also be necessary to identify certain major accomplishments of gradual change at each stage of evolution, because certain powers included in their natural perfection are what make it possible to try out the radical random variation that makes possible the next stage. That is how each stage contributes to overall course of evolution.

In the following sections, we shall derive the ten stages of evolution that lead up to rational beings like us. We shall see, in other words, how one stage of gradual evolution makes the next stage inevitable, staring with the beginning of evolution and tracing a series of stages that leads up to beings like us. The relevant levels of part-whole complexity in the structures of organisms have already been identified, and since each new stage is the evolution of the next higher level, we already know that they occur in a certain necessary sequence, if they occur at all. Thus, it remains to be shown that they do inevitably occur, and that will accomplished by showing that each is both possible and functional, given what is accomplished at the previous stage.

Though it is possible, in principle, for such a derivation to be formally compelling, what follows is only the outline of such an argument. Though the possibility and function of the level of organization that evolves at each stage will be shown, we shall not show what the natural perfection of organisms of each kind is by tracing the long course of gradual evolution. Instead, we shall use what has evolved on earth to tell what is naturally perfect (since it is ontologically necessary that gradual change in the direction of natural perfection occurs). And in some cases, the possibility of trying out the higher level of part-whole complexity will be only be shown to be probable. That is to leave the project of formulating this argument as a logical deduction until later, but it will identify the conclusions of those yet-to-be-constructed ontological arguments.

Though we shall follow out a series of stages that begin with biological evolution itself and lead up to beings like us, that is not to deny that there are other stages involved in the evolution of life on earth. Not much attention will be paid, for example, to the evolution of plants. And there may by other series of stages that branch off in other directions. But the one we shall trace is the most important one, because it leads to the organisms with the greatest power.

Natural perfection of life. The proof that evolution goes through a series of inevitable stages is proof that evolution by reproductive causation is change in the direction of natural perfection in a far grander sense that the natural perfection of organisms and ecology, which are the direction of gradual evolution at each stage. It is an additional form of natural perfection, which implies that each new stage has a function and is good in virtue of contributing the natural perfection of the whole of which it is part. I will call the increase in such levels the “natural perfection of life,” because each higher level of part-whole complexity in the natural perfection of organisms enables life generally to control a wider range of relevant conditions

Furthermore, if we recognize that evolution by reproductive causation is itself a kind of natural perfection because of how it makes the most of substances by using their endurance through time to bring about the natural perfection of organisms, the ecology and life itself, then each stage of gradual evolution (like each phase within each stage) also has a function and is good in virtue of making an essential contribution to the natural perfection of the whole of which it is part.

The natural perfection of life is a form of natural perfection of by our definition of doing the most with the least. In this case it does the most because it brings more and more conditions in the world under the control of living organisms (as structural causes), and it does it with the least, because the organisms with which it does so have the natural perfection of organisms and they are parts of an ecology that has the natural perfection of ecologies. This is not to say that life becomes absolutely perfect in this sense, but only that it is change in the direction it would have to go in order for life to be absolutely perfect in the sense of doing the most with the least. We will see in the chapters on What ought to exist what kind of perfection it leads to in the end.

It should be emphasized, however, that although higher level organisms would evolve only if they were more powerful in some way, that does not mean that organisms from lower levels must stop going through reproductive cycles on their own alongside the new organisms. The natural perfection of the ecology at later stages includes organisms from all previous stages, completing reproductive cycles side by side.

As we have seen, the varieties of organisms that come to exist during each stage tend to mirror the physical sources of free energy available in the region, and some sources are so limited that lower level organisms are more efficient in tapping them than higher level structures. They cannot easily be displaced by higher level organisms.

Moreover, though the advent of higher level organisms may displace lower level organisms from niches with larger sources of usable energy, they also provide new sources of usable energy for lower level structures to invade, for example, in their wastes, decaying bodies, or as diseases (such as viruses, bacterial infections, and eukaryotic parasites in multicellular organisms).

Thus, as higher level organisms of some kind are evolving toward natural perfection for organisms of their kind, there is also gradual evolution of organisms with all levels of part-whole complexity in the direction of the natural perfection of the ecology at that stage. Each species imposes natural selection on itself, and since organisms with different levels of part-whole complexity go though reproductive cycles side by side, they all become increasingly diverse and powerful, dividing up the free energy available among themselves to fuel their reproductive cycles. (As we shall see, the natural perfection of both the organisms and the ecology are usually involved in making the next stage possible.)

Biological stages of evolution. The basic series of levels of part-whole complexity in evolving organisms is the series of levels of biological organization, and we will use it to follow the course of evolution up to multicellular organisms. We will then take up, in order, the series of stages caused by the levels of neurological organization, including both the stages of animal evolution and the stages of spiritual evolution.

1. Molecular stage: RNA as a proto-organism. One of the biggest puzzles about evolution is how it began. Darwin did not try to explain it, speaking as if God has created the simplest organisms from which all the other species descended, and there is still no agreement on this issue. Indeed, it is sometimes called one of the great puzzles that natural science has yet to solve. But ontological philosophy affords a simple explanation of its beginning.

The beginning of evolution. What would solve this puzzle is a way of showing how the beginning of evolution is inevitable. Given that reproductive global regularities are ontologically necessary, that could be done by showing that, before biological evolution began, there is a region in which the ontological cause of gradual evolution exists, that is, in which there are complex material structures going through reproductive cycles.

Since the ontological cause of gradual evolution involves a kind of material structure that uses free energy to do work, the region in which they exist must be one in which there is a thermo­dynamic flow of matter (that is, a flow from potential energy through kinetic energy and photons to evenly distributed heat, according to the tendencies to kinetic energy and randomness). Such a region of increasing entropy is provided, as suggested at the end of Material global regularities, by the structure of planetary systems.

Stars involve fusion reactions, a form of the tendency of potential energy to become kinetic energy (and radiation), and thus, they supply free energy. And the surfaces of planets that intercept its radiation are a region within the thermodynamic flow where material structures could be using free energy to do work. Photons interact with molecules on the surfaces of planets, and that can produce molecules with energy-rich structures that supply, in turn, the free energy (as chemical potential energy) to drive many other kinds of interactions among molecules. Much of the energy eventually becomes kinetic energy, and the tendency to randomness distributes it evenly among objects on the micro level as heat (or bound energy) which cannot be used to do work. The planet tends, however, to have a certain temperature range, because it radiates low energy photons back out into the cold emptiness of space.

Since the right kind of region exists in planetary systems, all that is required for evolution to begin are organisms going through reproductive cycles. That may not seem possible before biological evolution begins. The surface of such a planet is composed only of naturally occurring molecules (that is, the kinds of material structures that come to exist naturally as a result of the tendency of potential energy to become kinetic). But even the simplest forms of life, such as bacteria and other prokaryotes, have a structure that is far too complex and functional to have occurred originally as a accident in the motion and interaction of molecules on the surface of a planet.

Organisms are nevertheless possible on the surface of such a planet, because what we mean by “organisms” is a complex material structure of the kind that can go through reproductive cycles and that can be surprisingly simple.

Organisms are complex material structures because they are bundles of structural causes with various structural effects. And to say that they can go through reproductive cycles is to say that these material structures can reproduce themselves as well as generate those structural effects as non-reproductive work. If they actually go through reproductive cycles, it is, as we have seen, ontologically necessary that such “reproducing organisms” will evolve toward maximum holistic power for organisms of their kind.

The ontological cause of gradual evolution we are seeking, therefore, could be as simple as a single molecule going through reproductive cycles. It would have to a rather complex molecule, but if it is possible, such a molecular level organism might be called a “proto-organism.”

The inevitability of evolution beginning. Given that there are regions where free energy is continuously supplied to molecules, what makes it ontologically necessary that such proto-organisms exist in a spatiomaterial world like ours is that the specific nature of matter makes matter is capable of forming itself into molecules of sufficient complexity (through the tendency of potential energy to become kinetic). We know that it is possible for molecules with complex enough geometrical structures to be proto-organisms, for we can conceive how a certain kind of molecule would be such an ontological cause.

Of course, knowing the molecular processes involved in life on earth makes it easier to think of this possibility. But it is clear that molecules are the simplest kinds of material structures that could possibly be the original bundles of structural causes going through reproductive cycles, because the natures of nucleons and electrons make only a few structures possible in atoms.

Given the nature of the ontological cause of gradual evolution, all that is necessary is that a molecule have multiple parts, each of which is the structural cause of both essential kinds of work, one by which it reproduces itself and one by which it helps construct another molecule — assuming that it actually goes through reproductive cycles in which it normally does both. It is possible for a macromolecule to have both kinds of structural effects, because it is a long chain of simpler molecules of a few kinds and there is a simple way that segments of such a molecule could do such basically different kinds of work.

Assume that matter is capable of enough complexity that the simpler molecules that are linked as parts of a macromolecule can form weak bonds (such as the hydrogen bond) with other simple molecules. And assume that when they attract the other simple molecules, the other simple molecules become linked to one another as a second macromolecule (with strong chemical bonds). There could then be parts of such a macromolecule that are capable of doing both essential kinds of work.

The macromolecule could reproduce itself when each simple molecule in the chain did such work on molecules of its own kind. And it could do non-reproductive work when short segments of such simple molecules in the chain did such work on molecules of a basically different kind, for that would be to construct another kind of macromolecule, whose structural effects would be the work it does. (See accompanying diagram of proto-organism as a bundle of structural causes each with two kinds of essential structural effects.)

Proto-organisms of this kind can be said to have a higher level of part-whole complexity than ordinary molecules, because they must have parts that are capable of doing both kinds of work. Those parts are the structural causes that are bundled together as a complex material structure that goes through reproductive cycles as a whole, and as depicted in the diagram, each structural cause is composed of three of the simple molecules that make up the proto-organism.

That puts proto-organisms on a rather high level of what has been called the “ladder of nature.” Even if we count all subatomic particles as being on the first rung, that puts atoms on the second rung, and since ordinary molecules are a third rung, proto-organisms would be a fourth rung. But it would be higher, if we took into account the levels of part-whole complexity among the parts of atoms, for setting aside the electrons, the nucleus of an atom may be composed of many nucleon, and each nucleon is composed of three quarks. These lowest rungs on the ladder of nature are relevant here, for as we shall see, each of the levels of biological organization above the original proto-organisms is another level of part-whole complexity and, thus, another rung on the ladder.

If any macromolecules that can serve as proto-organisms occur naturally on the surfaces of suitable planets,, there are probably at least several kinds of them, because it is a world in which matter has a nature that enables atoms to constitute molecules that are sufficiently complex and stable. Now, we know that it is ontologically necessary that, if proto-organisms were to go through reproductive cycles regularly for a long period of time, they would change gradually in the direction of maximum holistic power for proto-organisms of their kind. But that final condition could also be satisfied on planets that are not only in orbit around a star, but also rotating on their own axes.

The circadian cycle on the surface on the planet involves a regular change in the supply of free energy, and that is a way that at least some kinds of proto-organisms would be driven through reproductive cycles. Any kinds of proto-organisms that tended to do one kind of work during the day (when free energy was more abundant) and the other kind of work during the night (when less free energy was available) would go through reproductive cycles indefinitely. Hence, they would inevitably evolve.

Which kind of proto-organism would be responsible for the subsequent evolution on the planet (and thus, perhaps, how far evolution can go) would depend on which kind of macromolecule is most susceptible to this influence of the cycle of night and day and which kind had non-reproductive work that was most capable of controlling relevant conditions. We know which kind it is from what has actually evolved on earth. But what we know from the ontology alone is that there is a way in which it could be inevitable throughout the universe that macromolecules evolve in the direction of maximum holistic power for proto-organisms of their kind. It depends only on the large scale structure of the universe and the nature of matter, and since we know that those conditions are satisfied in our spatiomaterial world, we know there is a way that the beginning of evolution could be inevitable.

Thus, I shall take it to be an ontologically necessary truth that in a spatiomaterial world like ours it is inevitable that evolution by reproductive causation begin. It is not a logical consequence of spatiomaterialism itself, because it also depends on the specific nature of matter and structure of the universe. (We have assumed, for example, that matter is capable of such complexity that other naturally occurring macromolecules could serve as possible proto-organisms). But a conditionally necessary truth is sufficient for my present purpose, since I am merely outlining the ontological argument that could eventually show that the beginning of evolution is inevitable on earth. However, we must now consider how likely it is that the actual world satisfies those further conditions.

RNA as the original proto-organism on earth. Knowing how the beginning of evolution could be ontologically necessary, we know what to look for to discover whether it was inevitable that evolution begin on earth. We know that evolution did occur on earth, and thus, if it did begin with molecules of some kind serving as proto-organisms going through reproductive cycles, we can identify the specific kind of macromolecule in the molecular structure of the organisms on earth. Not surprisingly, it turns out to be RNA molecules. If we now see how RNA would play the role required by the foregoing ontological argument, we will learn something new about the nature of RNA.

Despair about explaining how RNA can evolve has, however, led some to look in entirely different directions to explain the origin of evolution. For example, some think it must lie in larger configurations of molecules, such as coacervate droplets, or micro spheres made of protein molecules, that naturally form in water. Others look favorably on even more extreme solutions, such as panspermia, the belief that the structure required for life is spread throughout the universe in the form of seeds, which grow on young planets.

RNA molecules are made up of some four different kinds of simpler molecules, nucleotides, linked together in long chains (by a sugar and phosphate backbone). What makes such macromolecules a likely candidate is that they reproduce their own structures when supplied with nucleotides, albeit inefficiently. (Each nucleotide exerts weak forces by which it attracts a complementary nucleotide so that the latter becomes attached to the new chain, and thus, after two rounds of reproduction, there is another RNA molecule of the same kind as the original.) But RNA molecules could be bundles of structural causes that also do non-reproductive work, because short segments of adjacent nucleotides could work together under different circumstances to attract simple molecules of another kind so that the latter also became attached to one another in long chains. (That is, different triplets of nucleotides could determine different kinds of amino acids in protein synthesis.) If RNA molecules are the bundles of structural causes that were doing both kinds of work, the synthesis of another macromolecule like themselves and the synthesis of a different kind of macromolecule, they could be the proto-organisms that were going through cycles of reproduction at the beginning.

If this is what RNA molecules were doing, they would not only be proto-organisms, but since they are composed of structural causes that are responsible for both kinds of products (reproducing themselves and determining a kind of amino acid), they would also be able to try out random variations on traits that are heritable by their offspring. Thus, if RNA molecules were to go through cycles in which they normally did both kinds of work, they would inevitably evolve.

Reproduction would cause their population to grow, and population growth would eventually make resources scarce. (The chemical processes by which molecules have effects like these depend on their having a supply of energy-rich molecules, and whatever the ultimate source of energy-rich molecules on the surface of a planet, the supply will be finite in any region during any finite period of time.) Thus, RNA molecules would eventually have to compete for resources to do the work involved in completing a reproductive cycle. Only the fittest would succeed in the end.

The range of variations would be large, for if the structural causes bundled together in these proto-organisms is each composed of three nucleotides from four different kinds, there are potentially as many as sixty-four different kinds of simpler molecules (amino acids) that could be linked together in the secondary macromolecule (the protein molecule). Thus, if the varieties of secondary macromolecules they could produce were potentially useful in controlling conditions that affect their reproduction, they would inevitably evolve greater power.

The primitive non-reproductive structural effect of RNA. This is how the beginning of evolution could have been inevitable. I say “could have been,” because biologists do not know that RNA were able at the beginning to generate the second kind of macromolecule and they must have done non-reproductive work of some kind in order to evolve. What is known is that RNA molecules produce such secondary macromolecules in all extant life forms. RNA guides the synthesis of protein molecules, or chains composed of twenty or so different kinds of amino acids (attached to one another by peptide bonds). And in life forms on earth, proteins are the molecular machines responsible for doing virtually all the work of controlling relevant conditions. But RNA molecules generate this kind of secondary product only in the presence of a very complex structure, called a ribosome, which is composed of many different kinds of complex proteins and other RNA molecules, and no such complex molecular machine could possibly have existed naturally at the beginning of evolution (that is, as a simple product of the tendency of potential energy to become kinetic energy).

The current need for ribosomes does not necessarily mean, however, that RNA was not the proto-organism with which evolution began, because RNA could have had a simpler and much less efficient way of catalyzing the synthesis of proteins under conditions that prevailed on the early planet.

When the RNA backbone was attached to a clay substratum, for example, certain triplets of its nucleotides may have been able to attract a few kinds of amino acids, thereby helping to attach them together in chains. Even a very inefficient way of synthesizing proteins involving only a few kinds of amino acids could have promoted the reproduction of the RNA molecules that synthesized them, for even very simple proteins could make a big difference in completing reproductive cycles. For example, simple proteins could help supply parts needed for reproduction (by preparing nucleotides). And some of the first powers to evolve would have been selected for making the synthesis of proteins more efficient, which would expand the range of possible non-reproductive structural effects. For example, one kind of simple protein might have helped attach RNA backbones to clay at an angle that promotes protein synthesis. Another might attach to RNA in a way that makes the synthesis start at a certain nucleotide, so that the triplet code was read the right way. At later points, new kinds of amino acids (or, perhaps, even the fourth kind of nucleic acid) may have been added to their repertoire, increasing the range of possible powers. Alternatively, other kinds of nucleotides or amino acids may have been going through a similar process, and they may have been left behind by the greater efficiency of the protein synthesis generated by those RNA molecules that are now parts of living organisms. In any case, with natural selection caused by their reproduction (that is, the scarcity due to their population growth), continual improvements like these on a primitive form of protein synthesis could explain where the ribosomes now found in all forms of life come from.

That is how evolution could have begun. That is, nothing known to biology shows that RNA did not have such a primitive way of generating secondary products. And if they did, not only the beginning, but also the course of evolution would be inevitable. As we shall see, such gradual change in the direction of natural perfection together with one episode of revolutionary evolution would explain the origin of life, and from there, it is clearer how it is inevitable that one stage follow another.

The original reproductive cycles of RNA. Assuming that RNA did have a primitive non-reproductive structural effect, it may still seem that evolution could not have begun this way in earth, because in order to evolve, RNA molecules would have to go through cycles continually in which they produced both kinds of molecules, and that hardly seems likely, given the complexity of the process of synthesizing either kind of molecule. The synthesis of either kind of molecule requires a series of steps in which one simpler molecule after another is attracted to the RNA molecule and attached to a growing chain. Thus, the fact that one and the same RNA must generate both kinds of molecules suggests that these two processes are likely to interfere with one another. That makes it seem that RNA could not go through reproductive cycles regularly enough over a long period of time for reproductive causation to have its inevitable effect.

The foregoing ontological explanation of the inevitability of the beginning of evolution, however, includes an explanation of why RNA molecules would have gone through reproductive cycles indefinitely. They were driven through reproductive cycles by the nature of the larger context in which evolution begins.

Earth is a planet, and as is widely assumed, life can evolve only on planets orbiting at the right distance from their stars for water to be liquid. Water provides a medium in which the kinds of chemical interactions on which both kinds of products depend are more likely to occur (if only because water stabilizes molecular structures by limiting the range of energies at which they interact). And radiation from the sun is a source of energy that fuels the chemical interactions that result in the energy-rich molecules used as resources by RNA molecules to generate their two products.

Thus, RNA could have been driven through reproductive cycles by the circadian cycle that occurs on planets that rotate on their own axis as they orbit their star. If RNA were disposed to produce one molecule during the energy conditions that prevailed during the day, and if they were disposed to produce the other kind of molecule during the energy conditions that prevailed at night, they would have gone through one cycle after another in which they generated both essential kinds of molecules (perhaps each of them several times during each cycle).

There is good reason to believe that RNA is susceptible to such an influence, assuming it can generate both kinds of products at all. Its reproduction requires only the free energy contained in the simpler molecules that it uses to construct another molecule like itself. (Nucleotides come with phosphate tails, and breaking them off supplies the energy needed to bond them together.) But the parts attached to one another in protein synthesis do not supply their own energy. They need other energy-rich molecules, which were probably most abundant during the day (such as ATP, or adenosine triphosphate). Thus, RNA could have been driven through cycles of reproduction by the cycle of night and day.

An ontological argument for RNA’s primitive non-reproductive structural effect. The need to assume that RNA had a primitive way of synthesizing protein molecules is the weak link in this demonstration of the inevitability of the beginning of evolution on earth. It is possible that RNA has no such structural effect. Some accident may be responsible for evolution beginning on earth. Or there may be some other way in which it is inevitable. But the capacity of spatiomaterialism to explain other aspects of the world, including, as we shall see, the inevitability of the subsequent stages of evolution, will make it seem likely that many more aspects of the world are ontologically necessary than it now appears to us. And if we suspect that evolution must have had an inevitable beginning, we can take this explanation of how it would be inevitable in a spatiomaterial world to be a reason for believing that RNA does have a primitive way of doing non-reproductive work.

Given the enormous variety of molecules made possible by the nature of atoms and the bonds among them that are stable on suitable planets, there were probably several kinds of macromolecules that could have served as proto-organisms by virtue of being bundles of structural causes that could do both kinds of work, that is, produce molecules of both essential kinds (reproducing themselves and constructing a secondary molecule),. However, they could evolve greater power only if they were to go through reproductive cycles regularly, and whichever kind of proto-organism was driven through reproductive cycles by the cycle of night and day (or was more susceptible to that influence) would have led to all subsequent evolution. (And if there were several kinds, the one with the most powerful structural effects for controlling relevant conditions would have led to subsequent evolution.)

It is possible, therefore, to identify the original proto-organism, if this is how evolution began and has been caused on earth. That proto-organism would still be doing both kinds of work, reproductive and non-reproductive, in existing organisms, because they would be merely higher level of part-whole complexity in the coordination of such behavior. The simplest structures doing both kinds of work in living organisms are RNA molecules.

Thus, if we believe that the beginning of evolution must have been ontologically necessary, like so many other aspects of the world, we discover something that empirical biology does not recognize. RNA had a primitive way of synthesizing proteins at the very beginning, for unless it was able to do non-reproductive work of that kind, it could not have been the proto-organism with which evolution on earth began. Thus, we predict that RNA molecules will eventually be discovered to be a structural cause capable, in suitable, natural circumstances, of generating a structural global regularity in which amino acids are assembled as a protein molecule.

All that has been demonstrated, however, is that it is possible that this is how evolution began on earth and, thus, that it was inevitable. When I argue, therefore, that the course of evolution is inevitable, as I shall at each of the subsequent stages, it should be understood as an ontologically necessary truth that depends on RNA having a primitive way of synthesizing proteins as well as on the specific nature of matter and large scale structure of the actual world.

This ontological explanation of the inevitability of evolution by reproductive causation does not imply that evolution begins in every planetary system.

Unless the planetary system forms out of the debris of super nova explosions, they will not have the heavier atoms needed for many of the more complex molecules that are needed for there to be proto-organisms of this kind. (But since stars that explode as super novas are rather large, they form early after the Big Bang and have rather short life spans. Thus, there is likely to be a supply of heavy atoms where middle range stars like the sun form.)

It is also necessary that a large range of different kinds of molecules actually exist and interact in the various ways possible for them. That is not likely on the surfaces of some planets. Some are too hot (and supply too much energy) for such molecules to exist, and others are too cold (and do not supply enough energy).

Furthermore, it has long been recognized that the kind of planet on which conditions are most favorable for a wide variety of molecular interactions are those on which the temperature allows water to be liquid and there is enough water to provide a medium in which larger molecules can interact. (Water moderates the kinetic energy with which other molecules can interact and, thus, makes it more likely that they will not be destroyed by the ambient motion and interaction. Not only is water one of the simplest stable molecules, making it rather abundant, but the range of temperatures at which it is liquid is exceptionally wide.) Thus, we can be sure that at least one planet in many, if not most, planetary systems around stars like the sun include one that is favorable for such a wide variety of molecular interactions.

Nor is it easy to rule out the possibility of evolution occurring under substantially different conditions, such as orbits in systems with binary stars or planets with only water and no land. If evolution is possible in such situations, it might follow a somewhat different course.

The Gradual Evolution of RNA. We assume, therefore, that RNA molecules were the original proto-organisms. But the original RNA molecules must have been simple, with only a few varieties, and barely able to go through reproductive cycles at all. Reproductive causation would, however, make them more complex, more diverse and better able to control the conditions affecting their reproduction. The major accomplishment of this first stage of gradual evolution is a much more efficient and reliable way synthesizing protein molecule, which helps make the second stage possible. But at this first stage, when the proto-organisms are so simple, there is a way that reproductive causation works on them at two levels of part-whole complexity.

Natural selection at the individual level. At the level of individual RNA molecules, reproductive causation leads us to expect that every new power to control relevant conditions would evolve as it becomes possible, that is, as random variations on extant RNA synthesize proteins happen to control some new condition that affects reproduction or controls some old condition better.

Those RNA molecules whose proteins controlled some relevant condition, such as supplying nucleotides for reproduction, would be more likely to reproduce, because they would be more likely to be located where RNA were benefiting from them. There would be random variations on them, because RNA reproduction is far from perfect. Kinds of nucleotides would be substituted, new nucleotides would be added, and whole RNA could be spliced together. Such random variations on existing RNA would sometimes alter the kind of amino acid used at some point in the protein or add new amino acids, and if these slightly different proteins or slightly more complex proteins were any better able to control the relevant condition, the RNA molecule producing them would be located where it was somewhat more likely to benefit from them and, thus, would be more likely to succeed in reproduction.

Since the triplets of nucleotides are the structural causes bundled together as a proto-organism, the relevant condition that is controlled by the work each does is determining which amino acid is appended in the growing peptide chain at some point. Different triplets of nucleotides in the RNA would control different relevant conditions by determining amino acids at other points in the protein being synthesized. Thus, reproductive causation would make these proto-organisms gradually more powerful over their whole reproductive cycles by altering the bundle of structural causes — shaping each structural cause to be as effective as possible in determining some amino acid, adding new structural causes when the amino acid they add makes the chain more power, and fitting those structural causes together harmoniously as parts of a single RNA — so that the RNA molecule eventually has maximum power over the whole cycle. But maximum holistic power for an RNA molecule is just whatever power comes from the kind of protein it produces existing in the neighborhood.

Even if evolution began with a single variety of RNA whose protein did some useful work, evolutionary change would not stop at making its protein as powerful as possible, because some random variations on existing RNA would synthesize proteins that controlled other relevant conditions. If the first kind of protein supplied nucleotides for RNA synthesis, there are surely random variations on its RNA template whose slightly different protein molecules would supply other kinds of nucleotides, or supply the same kinds of nucleotides in from other sources. Again, random variations on existing RNA that happened to control some new condition affecting RNA reproduction would be more likely to succeed in reproducing, because their location in the region would make the more likely to benefit. Thus, from the original RNA molecule(s) would evolve a variety of RNA molecules serving as templates for proteins with different functions, and each would become maximally powerful in serving its function.

Natural selection at the group level. The increasing diversity of RNA molecules would make their combination in local regions an ecology, and the most spectacular accomplishments of the first stage of evolution, such as a more efficient and reliable process of synthesizing proteins, would come from the increasing power of the ecology as a whole.

Natural selection would not be very selective at first. Though RNA whose proteins controlled some relevant conditions would be more likely to reproduce because they would be in the right location to benefit from the protein, other nearby RNA would also tend to benefit. But once there were enough different kinds of RNA whose proteins making different contributions to the reproduction of them all, change in the direction of maximum holistic power at the ecological level would be accelerated by a weak form of reproductive causation at the level of local ecologies.

Different local ecologies would be like different higher level organisms trying out different combinations of RNA. Each local region would contain various kinds of RNA, synthesizing various kinds of proteins, and they would all be driven through cycles of reproduction by the cycle of night and day side by side in the water. The varieties of RNA would be like the many structural causes “bundled together” like a higher level organism, for the proteins synthesized by all of them would tend to jointly control conditions in their local region that affected the reproduction of them all. And such ecologies of RNA molecules would also be able to reproduce as a whole, like higher level organisms, because when storms or other major disturbances scattered molecules to new local regions, and RNA that wound up in favorable circumstances where they could have both structural effects would start new colonies. Colonies with the right combinations of varieties of RNA would generate proteins of different kinds whose joint control of conditions affecting the reproductive of them all would make their populations of RNA grow faster. Thus, when the next storm came along, the more powerful combinations of RNA molecules would tend to populate the favorable locations when more normal conditions resumed. Random variations in bundling RNA together would be introduced by the reproduction of such “higher level organisms,” because the varieties of RNA that would wind up together in any given local region would be a mixture of varieties of RNA from several local regions. Since there are only so many favorable locations for such colonies of RNA to be set up, their reproduction would eventually make free energy scarce, and a natural selection would be made by the greater reproductive success of some whole colonies.

The relative lack of selectivity about natural selection at the level of individual RNA molecules would, therefore, make possible a powerful form of group selection, which would make the combination of different varieties of RNA in each region as powerful as possible as a whole in controlling all the conditions that affect RNA reproduction generally. Since random variations at the level of these higher level “ecological organisms” are made possible by how they are made up of RNA molecules as parts, there are three ways in which random variations may make them more powerful as a whole.

The first kind of change that occurs at the higher level of part-whole complexity (the local regions where RNA exists side-by-side in space) is the gradual change in each variety of RNA that shapes its protein to perform its function as effectively as possible. This is the gradual change described at the outset of this description of the gradual evolution of RNA, which itself involves three kinds of change because each RNA molecules is a bundle of structural causes, with each triplet of nucleotide determining the amino acid for some location in its protein molecule. Random variations on the RNA molecule that synthesizes it would try out variations on the protein, and the more effective varieties would tend to be the ones that succeed in reproducing, because they would be located in the local region where the condition was controlled and so there would be more of them to be scattered to new regions when a storm or other disturbance occurred.

Second, new varieties of RNA would be added to the colony when random variations on existing RNA happen to synthesize a protein that controls some new condition that affects their reproduction (or some old condition in a new way). Not only would it tend to be selected within the colony by its greater likelihood of being located where the protein’s benefit was provided, but it would eventually be added to the mix in other local regions. To take an extreme example, suppose that it alleviated some bottleneck in the process affecting them all. That would make all the RNA in the local region would be more successful in reproducing, and there would be more RNA from that colony to scatter to new local regions when the next storm came.

Third, the useful proteins that were being synthesized would also be shaped to work together as harmoniously and efficiently as possible with other proteins in local regions, because the reproduction of all the RNA molecules in the neighborhood is the joint result of the proteins synthesized by all the RNA. Thus, as different combinations of RNA molecules were tried out in different regions, those combinations that worked together most harmoniously and even assisted one another would tend to succeed, while less harmonious combinations would fail, because there would be more of them to scatter to new regions when storms or other disturbances occurred.

Reproductive causation was still weak, but since it was operating on the level of whole ecologies of RNA as well as on each variety of RNA within a local region, there would be an increase in the power of whole colonies of RNA to control conditions that affect the reproduction of them all. Although RNA molecules start off simple, weak and uniform, their stage of gradual evolution would eventually make them complex, powerful and diverse. Indeed, this would happen to whole colonies of RNA, because insofar as there is a range of different favorable locations for them, different combinations of RNA would evolve to tap the free energy available in all of them. The surface of a planet surely makes it possible for RNA molecules to go through reproductive cycles on a sufficiently large scale to try out all the random variations on existing RNA that are possible, and thus, each new relevant condition that could be controlled would be brought under control as it became possible.

More efficient and reliable protein synthesis. It is not necessary to trace the whole course of the gradual evolution of RNA, but it is worth mentioning what is probably its most significant contribution to subsequent evolution, namely, an efficient and reliable way of synthesizing protein molecules.

The original process by which RNA molecules synthesized the proteins that brought the first relevant conditions under control (such as supplying energy-rich parts for RNA replication) was probably weak and inefficient. The power to control relevant conditions of all kinds would have been greatly increased, therefore, by random variations whose proteins made the synthesis of proteins more reliable or powerful. There are many ways it could have been improved, including changes that expanded the kinds of amino acids that could be used. The first improvements may have been proteins that helped line up amino acids with the RNA and a substratum so that the protein chain was more likely to form. Such changes could have had far reaching effects, because it could give a function to previously useless proteins that were relatively abundant because they were so simple that they were continually being tried out, eventually selecting the RNA molecules that synthesized them. But the nature of the primitive means of protein synthesis is obscure, and the reason could be that major changes occurred its early evolution.

One indication that the original way of having a structural effect in addition to reproduction involved the synthesis of amino acids is that the successive bases, which are the information-carrying face of nucleotides, can be held together in chains by amino acids as well as by the phosphates used in RNA (and DNA). Such chains of amino acids are called "peptides," the chain that carries these bases are called PNA (rtaher than RNA or DNA). It means that amino acids interact with the molecules by which nucleotides determine which kind of amino acid to attach next in a way that could have occurred without the elaborate molecular machinery now used.

An example of a major evolutionary change would be the addition or deletion of the kinds of nucleic acids used. Protein synthesis may originally have involved only two or three nucleic acids and others were added as special proteins evolved that enabled them to use new kinds of amino acids in the proteins being synthesized. Or it may originally have used kinds of nucleic acids that interact more readily with amino acids and they subsequently dropped out when proteins evolved that enabled fewer nucleic acids to determine the amino acid to be added. It may even be possible that the original code used only two nucleic acids to identify which of the amino acids then being used were to be added, and later, assisted by new proteins, it was replaced by the three-nucleotide code found in existing living objects. But whatever the major changes were that occurred early in its evolution, they not only made it possible for RNA molecules to do their work more reliably and efficiently, but probably also increased the variety of amino acids used in constructing proteins from the few kinds that were probably involved at first to the twenty or so kinds of amino acids found in living objects.

Only 20 or so kinds of amino acids are used in synthesizing proteins, but they were selected from the enormous variety of amino acids that was availabe at the time. What singled these amino acids out was presumably that they provided enough variety for sequences of them to serve as all the kinds of molecular machines needed to handle other molecules. There is probably a geometrical aspect to the amino acids used that enables them to be combined in all the basic ways required to construct complex structural causes, and when it is explained, the currently intractable problem of predicing the conformations of proteins from their amino-acid sequence will have largely been solved.

Though the addition of new proteins to assist the process of protein synthesis would make such major changes possible, they would, at the same time, make the link between the nucleotides and amino acids more indirect. That would explain how the primitive way of synthesizing proteins evolved into its current, complex form. Even in the simplest forms of life on earth, protein synthesis depends on the interaction of RNA molecules with a complex machine composed of as many as fifty-five different protein molecules and three RNA molecules. "Ribosomes", as they are called, assemble themselves automatically in water because of their geometrical structures and how weak forces located on them bind them together. And they can consume only amino acids that have been attached as parts of tRNA molecules. But little is known about how ribosomes works, and when it is worked lut, there may well be empirical proof that original way in which RNA structural effects for doing non-reproductive work was a direct interaction between RNA and amino acids that linked them together in short chains.

2. Prokaryotic stage: DNA molecules. What evolves at the second stage are DNA molecules, which are a higher level of biological organization than RNA molecules, and the major accomplishment of this stage is the living cell, currently represented by bacteria and other prokaryotic cells.

In general, a new stage of evolution is caused ontologically by a higher level of part-whole complexity in the organisms that have already evolved. But as we have seen, in order to be a higher level organism, the lower level organisms must be bundled together as structural causes in a way that coordinates their behavior both in doing the work of reproducing itself and in doing the non-reproductive work that controls conditions affecting its reproduction.

An evolutionary stage in which organisms with a higher level of part-whole complexity evolves gradually in the direction of natural perfection for organisms of its kind is inevitable, if it is both possible and functional (that is, the higher level of organization can be tried out as a random variation and it is able to control an entire range of conditions affecting reproduction that were out of reach during the previous stage).

The inevitability of DNA proto-organisms. In this case, the lower level organisms are simpler proto-organisms, the RNA molecules that evolved at the first stage of evolution, though as we have seen, different varieties of RNA were to some extent combined in favorable regions where they all shared the benefits of the useful proteins being synthesized by any of them. And the upper level organism that begins the second stage of evolution is itself merely a higher level proto-organism, at least initially, for it starts off as just a way of attaching RNA-like molecules to one another as parts of a bigger macromolecule: the DNA molecule. DNA proto-organisms can, therefore, be the ontological cause of another stage of evolution, and a second evolutionary stage is inevitable, because such a higher level of biological organization is both possible and increases the power to control relevant conditions.

The possibility of DNA. There is no special problem about showing how it was possible for the evolved organisms to try out the radical variation that would begin the second stage, because gradual evolution during the first stage had already coordinated the behavior of RNA molecules in doing both kinds of work and useful combinations of varieties of RNA were already combined in favorable locales.

The DNA molecule, like RNA molecules, is a strand of nucleic acids linked by a sugar-and-phosphate backbone, but the kind of sugar used in DNA enables complementary strands of its nucleic acids to bind together and wind up as a double helix, which is a more stable molecule than strands of RNA. There is no reason to doubt that the range of random variations on the process of RNA reproduction was wide enough to try out DNA molecules made up of copies of evolved RNA molecules.

The random variations included the substitution of a new kind of nucleotide substituted for one of the (four) kinds used in RNA and a new kind of sugar backbone for holding members of the new set of nucleotides together as a DNA molecule. The single strand of DNA could then become a double helix by synthesizing its own complement, that is, by each nucleotide attracting its complement and binding them together as a second stand of DNA.

In order to go through reproductive cycles, organisms must be able to generate both essential kinds of structural effects, reproduction and various forms of non-reproductive work. That was possible in this case, because the various structural causes bundled together in of DNA molecules were copies of lower level proto-organisms that were able to do both kinds of essential work at the previous stage.

The DNA molecule could do non-reproductive work, because it contains multiple parts, usually called "genes", each of which has a geometrical structure that can serve as a template from which the RNA molecule (called messenger-RNA, or mRNA) can be transcribed. And DNA molecules could synthesize proteins in the established way, because the ribosomes and tRNA needed for protein synthesis had already evolved and were readily available in colonies of RNA in every local region. To be sure, transcription is a structural effect that requires the help of special protein catalysts. But natural selection was so inefficient at the first stage that they would be among the proteins being synthesized in at least some colonies of RNA. And a template for such proteins would be among the first genes included in DNA molecules, since their expressions would control a condition that affects their reproduction.

DNA reproduction also requires a special protein to promote it, but such a protein could be supplied in a similar way at first. And with the addition of one kind of nucleotide to those available in such colonies, DNA molecules would have all the parts they need to reproduce themselves in much the same way as RNA..

At the beginning, DNA molecules would be able to reproduce and control conditions affecting their reproduction, because there were favorable conditions. Colonies of RNA would provide most of the energy, parts, ribosomes and other housekeeping molecules, and DNA molecules themselves could direct the synthesis of the new protein molecules needed to control the condition affecting their own reproduction.

That is, by containing a gene whose protein facilitated transcription of mRNA and another gene whose protein facilitated its own replication, DNA molecules would themselves enrich the mix of molecules in the region sufficiently to go through reproductive cycles alongside RNA in the same regions, reproducing themselves and doing non-reproductive work during the same period of the circadian cycle as RNA.

The second level of biological organization illustrates a feature typical of biological levels: not only is the organism going through reproductive cycles on a higher level of part-whole complexity in space than the organisms from the previous stage, but each reproductive cycle of the higher level organism usually involves many reproductive cycles of lower level organisms. That is, in the biological levels, the reproductive cycles at the next stage have a higher level of part-whole complexity in time as well as a higher level of part-whole complexity in space.

DNA molecules generate non-reproductive structural effects by transcribing segments as mRNA molecules and using the mRNA molecules to synthesize a protein molecule, and this process may occur many times from the same gene.

The greater power of DNA. Nor is it difficult to see why this higher level of part-whole complexity in evolving organisms would be able to control conditions affecting reproduction beyond what was possible at the previous stage. The favorable environment provided by the gradual evolution of RNA toward natural perfection for proto-organisms of their kind is what made it possible for DNA molecules to go through cycles in which their parts (genes) did the non-reproductive work of synthesizing protein and they reproduced themselves as a whole. And DNA would evolve by reproductive causation, because they were also driven through reproductive cycles by the cycle of night and day, along with RNA.

The main source of the greater power of DNA to control additional relevant conditions is their higher level of part-whole complexity. They have traits with a higher level of part-whole complexity. They could generate many non-reproductive structural effects by directing the synthesis of various proteins, and thus, they could bring conditions under control that required special combinations of proteins. Some of the powers they evolved are described below.

Moreover, their higher level traits would evolve faster than colonies of RNA, because useful combinations of proteins would be selected more reliably by the success of a DNA molecule in reproducing as a whole than they were at the first stage. (Combinations of proteins were selected at the first stage by the success of the several independent RNA templates for those proteins being more likely to populate favorable regions when storms came because of their greater population.)

For example, when storms redistributed both RNA and DNA molecules, not enough of the RNA molecules may arrive at the same locale for any of them to be of much use. But DNA molecules with a useful combination of genes could direct the synthesis of a number of unusual proteins at a single location, and both DNA and RNA would be able to complete reproductive cycles.

Furthermore, the range of random variations from which a natural selection was made was likewise greater, because in addition to new genes, DNA molecules could try out new combinations of established genes (especially if, among the kinds of proteins that had evolved by then for interacting with DNA, there were some that could cut DNA molecules and link them together in different ways).

It is inevitable, therefore, that proto-organisms with a higher level of biological organization would begin a second stage of evolution. We know from our ontological explanation that, if reproductive cycles generated by higher level organisms are both possible and more powerful, they are inevitable and another stage of evolution will inevitably begin. And since, as we have seen, DNA molecules satisfy those conditions, they would begin a second stage of gradual evolution.

There may be other ways of combining RNA molecules as parts of a higher level proto-organism which could also go through reproductive cycles. But our ontological explanation of evolution as a global regularity implies that the most powerful among them becomes the foundation of subsequent evolution, and thus, we know from the structures of extant organism that DNA molecules were the most powerful.

Gradual evolution of DNA. Without tracing its course in detail, we can sketch some of the more significant accomplishments of the gradual change of DNA molecules in the direction of maximum holistic power for proto-organisms of its kind, and that will put us in a position to explain the origin of life.

Regulatory mechanism. As we have seen, its higher level of biological organization enabled DNA to do non-reproductive work requiring the cooperation of multiple protein molecules. But that was only the first step in the increase of power that was possible for this higher level organism, because power could increase with better coordination of the behavior of the RNA-level proto-organisms.

There is some coordination in the synthesis of proteins in the fact that their templates, or genes, are all parts of the same DNA molecule. That would make DNA molecules more powerful than RNA molecules, even if it was a random process that selected which genes on the DNA to use in synthesizing proteins. But DNA molecules could evolve far more powerful ways of coordinating the behavior of the lower level organisms, for there are mechanisms that can make the synthesis of special sets of proteins depend on the conditions that prevailed in the local colonies of RNA they encountered.

The geometrical structure of DNA would make such a random variation possible. When complementary strands of DNA wind up and form a double helix, the genes they contain cannot do either essential kind of work. Thus, if the DNA molecule was normally kept closed during the phase of the cycle when its structural causes were doing non-reproductive work (except, perhaps, for a certain region of genes whose proteins facilitated mRNA transcription, DNA replication, or universal housekeeping functions), it could serve as a mechanism for coordinating the non-reproductive behavior of the lower level organisms of which it is composed. It required only the evolution of genes whose proteins would respond to molecules in the region indicating that a certain condition prevailed by opening up certain segments of DNA, allowing the genes located there to be transcribed into RNA for protein synthesis, and closing them up again when the conditions changed.

The evolution of proteins that promote, repress, or de-repress segments of DNA would also enable DNA to generate discriminative responses to situations, controlling only the conditions that needed to be controlled. DNA molecules with such a regulatory mechanism could succeed in reproducing, while DNA molecules without it failed, because they would control relevant conditions more efficiently, that is, doing more with less.

The evolution of such a regulatory mechanism would enable DNA to respond to each situation in which it found itself by coordinating the behavior of its parts to control the conditions that happened to be relevant there. But that did not exhaust the new powers that were possible with a regulatory mechanism, because it also became possible to give the behavior of lower level organisms a temporal structure.

Once DNA had evolved the power to synthesize different combinations of proteins in response to different situations, the selection of rather minor random variations would make it possible for a single DNA to act on the world in a way that involved a series such coordinated responses. Messenger molecules signaling that some condition had been brought under control by one behavior could be the trigger for initiating another kind of behavior to control the next. The ability to make one change in the environment and then another when the first was completed would bring new relevant conditions under control.

Non-reproductive structural effects with a temporal structure could evolve for controlling new relevant conditions even though other relevant conditions in the region were being controlled more or less jointly (with RNA and its "housekeeping" proteins playing a supportive role to a variety of DNA in the region). It would make a difference locally which would tend to affect the reproduction of the DNA that generated the behavior, because it would be located nearby. But it would also enable its colony to be selected over others at the level of the group when storms or other disturbance redistributed all the molecules.

The cell. The power of this DNA-based regulatory system to coordinate the behavior of its parts as a sequence of responses to changing conditions was not fully exploited, however, until the evolution of a cell wall which enclosed all the molecular interactions generated by a single DNA molecule and isolated them from the surrounding colony. The cell, perhaps, marks the point at which proto-organisms evolve into something must be called an organism. The cell wall made it possible for complex sequences of behavior to add up reliably over time to a definite local result.

Cell-wall barriers may have evolved from the protein-based mechanism whose function was to keep regulatory proteins attached to DNA molecules after reproducing, for the reproduction of the whole DNA-based regulatory mechanism involved not only copying the DNA molecule itself, but also supplying new regulatory proteins for the copy made. This is consistent with prokaryotes, in which the loop of DNA remains attached to the cell wall.

Whatever their original function, however, once barriers became a wall separating the regulatory mechanism and its structural effects on molecules from the rest of the world, DNA molecules would be able to do non-reproductive work by generating behavior that involved complex sequences of RNA-level responses. The change made by each step in such a sequence could build on the effect of the previous step, and thus, the behavior of the cell as a whole could control conditions that were out of reach for naked DNA molecules.

There was, of course, a price to be paid for adding a cell wall to the DNA-based regulatory system. The cells were part of the structure that had to be reproduced along with the DNA molecules in order to reproduce the whole higher level organism. Thus, DNA would have to generate non-reproductive behavior that would construct a new cell wall during one phase, and it would have to divide the cell as part of its reproductive behavior during the other phase. But these are precisely the kinds of conditions that could be controlled by DNA with the ability to generate various combinations of proteins in sequences over time with cumulative local effects.

To be sure, once it was enclosed in a cell, DNA could not rely on RNA in the region to supply the “housekeeping” proteins, but had to include the genes that supply them. By the same token, however, this assured the natural selection of such DNA, for they could overcome the recurrent scarcity of parts and energy in RNA colonies by tapping sources of free energy in territories that were uninhabitable by RNA.

The evolution of cell walls once again increased the efficiency of reproductive causation. When the organisms going through cycles of reproduction were simply proto-organisms depending on the molecules available in a local colony to use free energy to do work, like RNA molecules, they were selected for synthesizing functional proteins by being located where their reproduction was more likely to be affected by them and by being reproduced in such numbers that they were more likely to wind up in favorable, local regions after a storm. Though reproductive causation does not need any more than a weak connection between useful non-reproductive work and reproduction, its efficiency is increased when natural selection is more discriminating.

DNA took the first step toward coordinating the behavior of RNA molecules by tying the fates of various genes together as parts of a single molecule, but, without a cell, the control of relevant conditions was still a joint project in each region, with different kinds of DNA benefiting from one anothers secondary effects and RNA playing a supporting role to all the DNA molecules located there by supplying the "housekeeping" proteins.

But once there was a cell to contain all the proteins synthesized by a single DNA, all the conditions required to go through a reproductive cycle could be controlled by a single organism. This concentrated the global reproductive cycle into many local reproductive cycles, and the cell as a whole became gradually more powerful in controlling all the conditions that affected its reproduction. (See diagram of reproductive cycle of nonliving organism.)

A DNA-based regulatory mechanism contained by a cell is the kind of complex material structure whose reproductive cycles constitute, along with space, the basic reproductive global regularity. It can go through reproductive cycles as a whole, because it can do both kinds of essential work. It coordinates the behavior of its genes to do non-reproductive work by transcribing mRNA whose protein products control relevant conditions, such as acquiring energy and parts from the environment and constructing more cell wall. It also coordinates the behavior of its genes to do reproductive work by transcribing mRNA whose proteins prepare for DNA replication, cell division, and carry out the sequence of changes involved in reproducing. But there is one further step that would make such cells even more powerful in controlling relevant conditions.

The Biological Behavior Guidance System. Even with the evolution of a cell wall, organisms based on DNA are still driven through reproductive cycles by the cyclic change in the supply of free energy due to the rotation of the planet. But this simple organism would be more powerful, if it could go through reproductive cycles on its own, independently of the circadian cycle.

Such cells would be more powerful because they would be able to go through reproductive cycles faster than organisms still entrained by the cycle of night and day, thereby consuming the free energy and parts before others could. They could also tap energy sources in locations that were previously uninhabitable because they were not affected in the right way by the circadian cycle.

In order to complete reproductive cycles on its own, however, it needed a system for selecting which of the two essential kinds of behavior to generate at any moment and for generating it, because DNA cannot transcribe mRNA and replicate itself at the same time.

Such a system required only a relatively minor change. Since the DNA-based regulatory mechanism could already express different genes depending on the kinds of messenger molecules present at any moment, the presence of a messenger molecule indicating that the cell had gathered enough energy and grown large enough could trigger the switch to reproduction. And it could switch back to growth again when another kind of molecule, which was present only when reproduction was complete, opened up the growth-genes. But since the chemical interactions involved in doing both kinds of work evolved under the energy conditions imposed by the cycle of night and day, it may also have required other new protein mechanisms to adapt them to the new conditions. (For example, to synthesize proteins at night, it may have had to replace the free energy formerly provided by high energy photons).

Let us call this mechanism for coordinating behavior the "biological behavior guidance system." Though some of its functions have been served by DNA from the beginning, all the steps we have traced in its gradual change in the direction of greater power must be traversed before DNA has accumulated the additional material structures required to be the ontological cause of all the structural global regularities needed to go through a cycle of reproduction on its own (when the region contains free energy that it can tap and other resources, such as the parts it needs for doing both kinds of work).

A higher level of part-whole complexity in organisms going through reproductive cycles is what causes a new stage of gradual evolution, and that requires the higher level organism to have some way of coordinating the behavior of the lower level organisms. That was done implicitly by DNA from the beginning by combining many genes, the equivalent of RNA proto-organisms, as parts of a single complex molecule, and we have traced how reproductive causation gradually increased the complexity of the higher level proto-organism, adding regulatory proteins and a cell wall, so that the higher level organisms could, as a structural cause, generate more complex behavior as a whole. Finally, the behavior it generates as a whole comes to include selecting between growth and reproduction and generating each of them when selected. At that point in the second stage of evolution, it serves all the functions of a biological behavior guidance system.

Though behavior guidance is a form of non-reproductive work that controls reproduction, that does not erase the difference between reproductive and non-reproductive work. An organism is still a bundle of structural causes, and in addition to coordinating all their behavior, it must be able to reproduce its structure as a whole. Reproduction is still unique: it is the construction of a material object with a geometrical structure like itself. And reproductive work requires parts throughout the whole prokaryotic organism to move and interact with one another in a fundamentally different way from non-reproductive work. Besides copying its DNA molecule and synthesizing regulatory proteins for its offspring, it must divide its cell by dismantling it in some places and constructing new cell wall in a different way from simply growing. That requires the DNA molecule and its regulatory mechanism to move and interact in basically different ways from doing non-reproductive work. What is different when the biological behavior guidance system evolves is that selecting when to reproduce becomes one of the kinds of behavior generated as part of its non-reproductive work, that is, a structural global regularity involving the transcription of mRNA and synthesis of proteins. That means it must set up the conditions that will not only result in its reproduction, but also put the biological behavior guidance system back in a condition in which it can select and generate other kinds of behavior when it is done reproducing. Thus, when the non-reproductive work of the cell comes to include selecting between phases of growth and reproduction, that does not make reproduction a form of non-reproductive work, but merely controls when reproduction occurs.

With the evolution of a biological behavior guidance system in the DNA-containing cell, what exists are organism of the same kind as bacteria, which are called “prokaryotes” or “prokaryotic cells.”

The prokaryotic biological behavior guidance system is the locus of changes in subsequent evolution. Those evolutionary changes are all basically kinds of non-reproductive work, or behavior, which the prokaryotic cell uses to control additional conditions that affect its reproduction, and since the biological behavior guidance system is an aspect of the geometrical structure of the whole organism that can determine whether it grows or reproduces, relatively minor modifications in that structure can select among and generate additional kinds of behavior. It is based on the regulatory mechanism, whose function was to generate various kinds of complex structural effects, but when it becomes part of a biological behavior guidance system, as aspect of the structure of the whole prokaryotic cell has the function of selecting and generating all its behavior. Thus, the evolution of new kinds of behavior involve changes in the behavior guidance system.

The origin and nature of life. Having show how the cell-enclosed DNA-based regulatory system evolves into a full-fledged biological behavior guidance system, we have derived from spatiomaterialism a material structure of the kind that is ordinarily said to alive. No one doubts that prokaryotic cells, such a bacteria, are living organisms. That would mean that in a spatiomaterial world like ours, the evolution of life is inevitable. It is one of the powers that organisms acquire during the second stage of evolution.

Life does not begin, therefore, deep in the ocean where heat is vented from the center of the Earth. It cannot, because there is no cycle in the supply of free energy, like the circadian cycle near the surface. It only appears to be where life began, because that is the ecological niche to which prokaryotes adapted that has changed least since the origin of life, and so it contains some of the earliest models of prokaryotic cells (called "archebacteria").

It is worth noting, however, what this explanation of its origin implies about the nature of life, for it suggests that life has an essential nature. To say that life has an essence is to say that there is a real difference — not just in our minds, but in the nature of things — between living and non-living organisms. Our ordinary understanding of life can tell us where to look for the difference, but in order to be sure what the nature of life is, those intuitions must be confirmed by an ontological cause. Life is a product of reproductive causation, but there should be some moment between the lifeless molecules with which evolution begins and the complex living organisms to which it leads, when a change occurs that is so basic that we recognize it as what our intuitions were seeing only confusedly.

Our ordinary conception of the nature of life seems to be captured by the notion of autonomous activity, given that it occurs naturally, rather than as just an artifact designed by beings like us. By "activity", I mean, not just a disposition, or physical property of the kind mentioned in the last chapter, but rather a more complex kind of goal-directed behavior in which different kinds of dispositions are generated in concert and feedback from these consequences is used to bring about some kind of overall change. And by “autonomy,” I mean that different kinds of activities are determined, not merely as responses to conditions that arise, as if they were guided by feedback in attaining some further goal, but rather internally, by something that selects among them. These are the traits to which we would point in order to remove any doubts that more highly evolved organisms are alive, and if we survey the significant steps in gradual evolution toward greater power, the step at which life begins may stand out.

We called RNA molecules “proto-organisms,” because they are already complex material structures that can do both essential kinds of work. (Each nucleotide attracts its complement in reproducing itself, and each triplet attracts a certain kind of amino acid in the non-reproductive work of protein synthesis.) Though they are on a higher level of part-whole complexity than most ordinary molecules, those ways of doing work are just dispositions, that is, mere physical properties. They are hardly “activities,” and there is nothing “autonomous” about them, since they are entrained by the circadian cycle.

The DNA molecule’s higher level of part-whole complexity enables it to coordinate the behavior of many RNA-level proto-organisms in doing both kinds of work. But neither kind of structural effect involves goal-directed behavior. Though its behavior as a whole may involve the synthesis of various protein molecules, they do not use feedback from the consequences of previous behavior to generate the kind of behavior that brings about some goal. It is still not activity in the relevant sense.

With the evolution of a regulatory mechanism, however, the DNA's higher level of organization does make the use of feedback possible. DNA can respond to different situations in different ways, and thus, the whole complex surely coordinate the behavior of many RNA-level organisms in one way in response to the consequences of coordinating the behavior of other RNA-level organisms in some other way. Though the use of feedback to attain the same goal in different ways in different situations makes it goal-directed, it is not yet enclosed in a cell wall, and so it is still just a series of responses that is largely controlled by the environment. Its activity lacks autonomy.

Enclosing the DNA-based regulatory mechanism within a cell makes its goal-directed behavior more autonomous, because it is able to coordinate the behavior of many lower level proto-organisms as a sequence of responses within its cell, each of which may depend on feedback from the last, and thereby carry out a temporally complex activity. That is what justified calling it an “organism,” rather than a mere “proto-organism.” But its activity is not fully autonomous, because its goals are given. Though such behavior may pursue different goals in different situations, the cell is not fully autonomous as long as its goal depends on the situation. Since its goals are still just variable means to a more encompassing, constant goal, the cell does not seem to alive. It is arguably just reacting to changes in its environment in ways that attain some overall goal, which is not itself chosen.

This final objection is overcome, however, when the cell-enclosed DNA-based regulatory mechanism evolves into a biological behavior guidance system, because at that point, its goals are not all dictated by changes in the environment. What determines when to grow and when to reproduce is no longer the circadian cycle, but the cell itself. It selects which goal to pursue for itself, depending on its own condition, mainly whether it has grown sufficiently large. Growth and reproduction are both goal-directed activities, but they are not simply sub-goals pursued as means to some constant overall goal. They are the two basically different kinds of work that an organism must do in order to evolve by reproductive causation.

Reproduction is not the goal of non-reproductive work, as we have seen, but rather the cause of evolutionary change. What changes is mainly the non-reproductive work. The organism acquires ways of behaving that make it increasingly powerful at controlling conditions that affect its reproduction, and the control of such a condition is the goal of every non-reproductive structural effect. What makes non-reproductive work functional is contributing to the holistic power of the organism. Thus, its function is not reproduction. Though reproduction may be a goal-directed activity, it is merely the kind of activity that causes population growth, scarcity and natural selection and does not itself have a function.

Furthermore, the power to choose between growth and reproduction on its own is, as we have seen, a form of non-reproductive work. It is another condition that is controlled by its behavior as a whole, that is, by coordinating the behavior the organisms of which it is composed. The cell-enclosed DNA-based regulatory mechanism opens up special segments of its DNA for transcription into mRNA and translation into proteins, while closing other, in order to set up the process by which it reproduces. That is the original function of the biological behavior guidance system.

The reason for calling this mechanism a “behavior guidance system” is that its function is not merely that of a mere cybernetic system, which uses feedback to adjust behavior in order attain some constant goal, but selecting between incompatible kinds of behavior. In the case of the biological behavior guidance system, it is selecting between phases of growth and reproduction, which cannot be generated at the same time. (There is, as we shall see, an additional kind of choice between goals that must be made in animals, and thus, the mechanism that serves that function will be called the “animal behavior guidance system.”) The function of selecting between incompatible kinds of behavior requires the behavior guidance system to have a structure that also serves to two other functions: input and output. It must have input from appropriate conditions in the world (including conditions in the organism itself) in order to select the right kind of behavior, and it must be able to generate one or another kind of behavior as output. In all, therefore, three functions are involved in behavior guidance, one involving choice, another involving input for making that choice, and a third for generating the behavior chosen as output. It is the output of a behavior guidance system that corresponds to a cybernetic system, because generating behavior often involves the use of feedback to guide it toward the goal that has been chosen. Although feedback also requires a kind of input, it does not necessarily use the same input mechanisms as the those that serve the function of choosing, for these input have different functions.

Judging by what is ordinarily meant by “life,” therefore, life begins when reproductive causation produces organisms with a biological behavior guidance system, for at that point, they can decide for themselves when to switch from pursuing one of at least two incompatible goal-directed activities. Though choosing between these goals still depends on input indicating when it has grown large enough or when reproduction is complete, it is autonomous in the sense that it is no longer merely responding to its environment as an external master. These cells are able to go through cycles of reproduction on their own, independently of the cycle of night and day. Life begins, therefore, when reproductive causation makes organisms powerful enough to remove themselves from the natural mold supplied by the large scale structure of the universe, the circadian cycle, and go through reproductive cycles on their own. Life begins with the autonomy of selecting between the two basic activities involved in reproductive cycles.

This concept of the essence of life implies that viruses and plasmids are not alive. They do not have a way of selecting between their two kinds of mechanical effects, but rather depend on living objects around them for their reproduction, just as primary structures did before the evolution of life.

This intuition about the essential nature of life is confirmed by its ontological significance, for the autonomy of the cell's activity marks a dramatic change in the ontological cause of evolution. We called organisms going through reproductive cycles the ontological cause of gradual evolutionary change, because given the wholeness of space, their motion and interaction had to add up over time to a global regularity in which their non-reproductive work becomes increasingly powerful at controlling relevant conditions. But such reproductive cycles are just a derivative ontological cause, since they are constituted by more basic ontological causes. And until the evolution of the biological behavior guidance system, the ontological causes constituting reproductive cycles were of two radically different kinds: the organism itself as structural cause generating both kinds of work and the large scale structure of the universe. The latter supplied not only the free energy required for the structural cause to do work, but also the temporal structure of the reproductive cycle, the cycle of night and day. However, there was a radical change in the ontological cause of evolutionary change when life evolved. Reproductive cycles become the autonomous activity of material structures. That is, the structural cause took over responsibility for the temporal structure of the reproductive cycle, leaving the large scale structure of the universe merely the role of supplying the free energy to be consumed in doing work. Thus, except for how reproductive cycles still depend on a supply of free energy, the beginning of life meant that the ultimate ontological cause from which the ontological cause of evolution derives is a complex material structure.

This dramatic change in the ontological cause of evolution means that, from this point on, evolution is something that organisms do to themselves. What causes natural selection, according to reproductive causation, is reproduction itself, because the multiplication of organisms in the region causes scarcity. As long as proto-organisms or organisms were driven through cycles of reproduction by the cycle of night and day, natural selection could be seen as something that was being done to them. But when the biological behavior guidance system evolved, structural causes not only do both essential kinds of work, but also generate the temporal structure of the cycle as a whole. Thus, evolution becomes something that living organisms do to themselves. Evolution still depends, of course, on the free energy supplied by its star. But given such a thermodynamic flow of matter from potential energy through kinetic energy and photons toward evenly distributed, life itself is what makes life evolve. That seems to be ontological confirmation enough of our intuition that life is essentially the kind autonomous activity that begins with the evolution of the biological behavior guidance system.

3. Eukaryotic stage: the nucleus. We have seen how the first two stages of evolution are caused by the first two levels of part-whole complexity in the organisms going through reproductive cycles, RNA molecules and those based on a single (looped) strand of DNA. And we have seen why those stages are inevitable. We identified the third stage of evolution when we were considering the levels of part-whole complexity in organisms on earth that might serve as ontological causes of evolutionary stage (in Change: Global: Revolutionary: Cause), because there are cells that are far more complex than prokaryotes, namely, eukaryotes, or cells with a “true nucleus.” They exists as independent organisms, but since they are basically the kind of cells that make up multicellular organisms on the fourth level of biological organization, they are an essential stage in the evolution of animals like us. In this case, however, it is not so obvious that the eukaryotic stage is caused by a higher level of biological organization.

Eukaryotes do not have the kind of structure we might expect on the model of the previous stage. Prokaryotic cells are not merely bundled together as parts of a larger structure, like RNA-level genes contained side by side in a DNA molecule — or for that matter, like cells in a multicellular organism. We have seen how it is plausible, nevertheless, to hold that eukaryotic cells have prokaryote-like parts. But the eukaryotic-level structure of which they are parts is so obviously functional that explaining its origin is problematic. It does not seem possible that the eukaryotic cell could have originated as a radical random variation on prokaryotic cells, and thus, the third stage does not seem inevitable.

Inevitability of eukaryotes. In order to derive another stage of evolution, given our ontological explanation of stages as a reproductive global regularity, we must show that a higher level of part-whole complexity in evolving structures is not only functional (in the sense of affording greater power to control relevant conditions), but also possible (in the sense that it can be tried out as a random variation on the organism that have been evolving at the current stage). In this case, the functional structure of eukaryotes makes it easy to see that they are more powerful than prokaryotes and can evolve an entire range of new powers that are out of reach for prokaryotes. But that same structure makes it difficult to see how they would ever be tried out as a random variation on prokaryotes even toward the end of their gradual evolution in the direction of natural perfection.

There is, however, an explanation of their origin that shows the eukaryotic stage to be inevitable. It has to do with how the higher level of organization that starts a new stage of evolution is not just bundling lower level organisms together, but also a way of coordinating the behavior those many lower level organisms. That is clearly what the nucleus of the eukaryotic cell is doing, and as we shall see, that function explains its origin. But before taking up the question about its possibility, let us be clear about the way in which organisms at the eukaryotic level of biological organization are inherently more powerful.

Greater power of eukaryotes. What distinguishes eukaryotes from prokaryotes is their nucleus, after which they are named. The nucleus is one indication of its higher level of biological organization, and by comparing the nucleus with the prokaryotic biological behavior guidance system, we can see how it is a new kind of biological behavior guidance system that makes eukaryotes far more powerful than prokaryotes.

Prokaryotic Cells. In the prokaryote, as we have seen, the biological behavior guidance system is a loop of DNA that is attached to the side of the cell wall that coordinates the behavior of RNA-level parts.

The cell’s behavior is generated ultimately by the synthesis of proteins, and behavior guidance is a structural global regularity caused ontologically by the structure of the prokaryote as a whole. Certain kinds of genes are selected for expression at any moment because of how the interaction of certain proteins with the DNA loop promotes the transcription of mRNA from certain segments of DNA, represses transcription from others, or de-represses transcription. When mRNA are translated into proteins (with the help of ribosomes), proteins interact with other molecules within the cell, and thus, the cell as a whole behaves. Behavior can depend on the situation, because the proteins triggering the expression of certain genes can be “messenger molecules” which are present only when certain conditions hold.

The same structural cause is responsible for the whole cycle of reproduction. The selection of certain segments of DNA for expression as proteins leads to the growth of the cell (including the acquisition of energy and parts, the construction of new cell wall and other non-reproductive work), and the selection of other segments of DNA reproduces the cell as a whole. After preparing the protein molecules required, the loop of DNA is replicated, the cell is divided, and one copy is enclosed in each new cell.

Thus, the prokaryote is lead through its cycle of reproduction by a simple, ratchet-like process that exposes certain segments of DNA and covers up others in lockstep with proteins that signal the success of each kind of behavior in the sequence, including growth and reproduction, at a minimum.

Eukaryotic Cells. The most obvious difference between eukaryotes and prokaryotes is the presences of a nucleus within the eukaryotic cell. The nucleus is one indication of the eukaryotes higher level of biological organization, as we have seen, it contains multiple chromosomes, each of which is roughly equivalent to one (or more) of the prokaryote’s loops of DNA. Each chromosome is also a DNA molecule containing many genes, but it is not a loop, it is much longer, and it is “complexed” with proteins.

That is, the parts of each chromosome are held together by a scaffold, and they can be drawn together in a tight, condensed form in order to be pulled around during reproduction. Normally, the strand is periodically wrapped around small proteins, like beads on a string, preventing transcription into mRNA.

Because the eukaryote has multiple chromosomes, it needs a nucleus to coordinate the expression of genes on different chromosomes at once. Since that it to coordinate the behavior of the lower level organisms bundled together in this higher level organism, the nucleus serves as its biological behavior guidance system. The nucleus selects and generates both essential kinds of behavior: growth (including various kinds of non-reproductive work) and reproduction (the construction of another object like itself).

The eukaryotes behavior is also generated ultimately by the synthesis of proteins. During periods of growth, the nucleus receives input from other parts of the cell (and the situation outside the cell) by messenger molecules transported into it. An interaction between those proteins and the chromosomes exposes certain segments of DNA on various chromosomes for transcription into mRNA, thereby selecting a kind of behavior for each situation. Behavior is generated as mRNA flows outward from the nucleus to the outer cell, where it is used to synthesize proteins (with the help of ribosomes). The flow of molecules is channeled throughout the cytoplasm by complex plasma membranes (the endoplasmic reticulum), and as protein machines interact in the outer cell, they generate the behavior of the cell as a whole.

Reproduction is an enormously complex process in which the chromosomes are replicated, the nucleus is dismantled, centrosomes form a spindle that divides the chromosomes, two new nucleuses are constructed, one for each copy, and the cell as a whole divides.

Though the behavior of the eukaryotic cell, like any machine, ultimately depends on its whole structure, its structure as a whole is such that its behavior is guided by only part of it, the nucleus, its behavior guidance system.

With the ability to express genes on multiple chromosomes at the same time, eukaryotes are able to coordinate the behavior of many prokaryote-level organisms, and thus, they are able to control conditions that are out of reach for solitary prokaryotes. That is, the source of greater power, as for all levels of biological organization, is the higher level of part-whole complexity itself. Size is a source of power in a world of space and matter.

Possibility of eukaryotes. In order to prove the inevitability of a new stage of gradual evolution, according to our ontological explanation of evolution, it is necessary to show both its possibility as well as its inherently greater power. Though the greater power is obvious, its possibility is problematic. It is not easy to see how its higher level of part-whole complexity could be tried out as a variation that somehow occur during the previous stage at the lower level approached maximum holistic power for organisms of their kind. The way that lower level organisms are bundled together in the eukaryotic cell is so highly organized and functional that it could not possibly have begun as just a random variation that happened to occur one day in the motion and interaction of prokaryotes and other molecules. Such an accident would be as incredible as supposing that life itself began as a random variation in molecules moving and interacting at random on the surface of a planet.

On the other hand, there is good reason to believe that prokaryotes played an important role in the evolution of eukaryotes, because there is another indication, besides a nucleus with its multiple chromosomes, of the eukaryote’s higher level of biological organization. It is the presence of mitochondria (in animals) or mitochondria and chloroplasts (in plants) in the cytoplasm outside the nucleus. These organelles are like organisms at the prokaryotic level of biological organization, because they contain their own DNA and reproduce themselves in the cytoplasm. Indeed, it is widely assumed that they are descendents of prokaryotes that existed about the time eukaryotes evolved. But their role in eukaryote evolution is unclear, because of the functional way that these lower level organisms are “bundled together” in the higher level organism. Though the behavior of these organelles is also coordinated by the nucleus, they are combined in the cytoplasm with a rich variety of other organelles that are constructed from molecules (and torn down) as part of the eukaryotic level behavior generated by the nucleus. What is needed is an explanation of the origin of those other structures in the eukaryote.

Received explanations of the origin of eukaryotes. Current speculation about the origin of eukaryotes is not very helpful in showing the inevitability of eukaryotes.

For example, it is not likely that one kind of prokaryote enslaved others, because prokaryotes are so equal in their abilities. And it does not explain the origin of the nucleus in any case, for it is very unlike a prokaryote.

Others suggest that the nucleus was originally an entirely different form of life that enslaved prokaryotes to exploit them for energy. But in order to explain the origin of the nucleus, there must have been a second origin of life entirely independent of prokaryotes. And if it needs prokaryotes as a source of energy, it does not explain where the nucleus obtained the energy that enabled it to enslave the prokaryotes -- or why it would bother, if it already had a source of energy. In any case, there is no trace of any such independent kind of living objects.

Lynn Margulis, a professor botany at the University of Massachusetts at Amherst, has proposed other possibilities, in which eukaryotes began as prokaryotes in which chloroplasts and mitochondria were invaders that were transformed into slaves. But like the predator hypothesis, it does not explain where the nucleus came from or how such an energy-consuming mechanism could evolve without prokaryotes to perform its energy functions.

Metabolic clue to the origin of eukaryotes. The clue that points the way to an explanation of their origin is, however, the energy function of chloroplasts and mitochondria in eukaryotes, at least, when we assume that stages of biological evolution are caused ontologically by organisms at one stage becoming organized as multiple parts of higher level organisms that go through reproductive cycles as a whole. That suggests that the eukaryotic structure was tried out, not on the model of enslavement or warfare, but on the model of cooperation. It could have been a result of change at the ecological level in the direction of maximum holistic power and a form of group level natural selection, as in the case of RNA evolution.

The function of the prokaryote-like organelles in eukaryotes is to acquire and process energy. Chloroplasts are organelles that trap the energy of photons in energy-rich molecules, and mitochondria are organelles that use oxygen to dismantle energy-rich molecules all the way down to water and carbon dioxide. Though they lack rigid cell walls, these organelles appear to be descendants of prokaryotes because they contain their own DNA and reproduce by binary fission in the cytoplasm of the eukaryotic cell. (Since chloroplasts contain chlorophyll a and b, whereas blue-green algae have only chlorophyll a, chloroplasts probably derive from the ancestors of Prochlorphyta, a recently discovered kind of prokaryote that contains both chlorophyll a and b.)

These organelles are the basis for classifying single-celled eukaryotes, or “protists,” into three basically different groups. Plant-like, animal-like, and fungus-like – are simply the three ways of exploiting the three prokaryotic methods of acquiring and processing energy.

Plant-like protists, which contain both kinds of organelles, are autotrophs, because (with chloroplasts to absorb energy from the sun and store it in energy-rich molecules and with mitochondria using “respiration” to turn those energy-rich molecules into free energy that can be used by molecular processes in the cell) they need only simple inorganic molecules, which are available everywhere, to complete their cycles of reproduction.

Animal-like protists, which contain only mitochondria, are heterotrophs, because they obtain energy-rich molecules from the environment to fuel behavior by incorporating other living objects as parts of themselves.

Heterotrophs that lack both kinds of prokaryote-like organelle are fungus-like protists, such as yeast, which use fermentation, the first way that prokaryotes found to process energy, to fuel behavior. (Fermentation releases only a fraction of the energy that respiration could extract from the energy-rich molecules, and thus, they are much less active than animal-like protists.)

What the ontological explanation of stages of evolution suggests is that the energy function of chloroplasts and mitochondria were coordinated in some way long before eukaryotes evolved, so that the nucleus was tried out as a variation on the natural perfection of certain ecologies of prokaryotes.

What I will describe here is speculative, and it is probably mistaken in some details. But such errors are not crippling in this case, because it still shows that it was possible for the evolution of prokaryotes to lead to a variation that made the eukaryotic level of biological organization inevitable. It is something like a “second origin of life,” but it is just as inevitable as the first origin of life.

There may be simpler ways in which the eukaryote level structure could be tried out by random variations, but they would also show the inevitability of the third stage. And as long as there are no such possibilities, this one can serve as a model for discovering the details about how it did happen.

The origin of eukaryotes. Traces of prokaryotes apparently date back about 3.5 billion years, within a billion years after the formation of the Earth. But since there are no traces of eukaryotes until about 1.4 billion years ago, prokaryotes probably had been evolving for about two billion years before eukaryotes showed up. Eukaryotic cells and multicellular organisms both evolved well before the Cambrian era, some 0.6 or 0.7 billion years ago, when the detailed fossil record begins. Empirical evidence leaves us in the dark, therefore, about how eukaryotes originated. But with the help of what we know ontologically about evolution, it is possible to see how it is would have been inevitable that eukaryotes evolved.

Aquatic balloons. Eukaryotes must have evolved after prokaryotes had discovered all three basic energy strategies and filled all the ecological niches that were possible for them in the habitable space near the surface of Earth. Fossils that date back 1.4 billion years suggest that the first eukaryotes were plant-like protists that floated near the surface of the ocean. This suggest that eukaryotes evolved when photosynthesizing prokaryotes happened on the trick of constructing a plasma membrane to contain them, thereby floating themselves together near the surface. The molecules making up plasma membranes form themselves into spheres in water that are relatively impermeable to larger molecules.

The plasma membrane is made of phospholipid molecules (simple sugars with a pair of long hydrocarbon tails on one side and an organic molecule attached to phosphate on the other). When phospholipids are lined up side by side, like matches, forming a two-dimensional sheet, there are weak bonds among them (Van der Waals forces, which come from synchronizing the electric forces exerted within each molecule), but since such bonds hold on all four sides of each tail, they are strong enough to preserve the configuration. Furthermore, the phosphate ends of the molecules have residual electric charges that attract water molecules (which also carry such residual charges), whereas the lipid ends of the molecule lacks any residual electric charge and thus do not attract water molecules. In a watery medium, as a result, water molecules tend to gather on the hydrophilic sides of the sheets that they form, thereby pushing the hydrophobic sides of the sheets together and forming a membrane of two layers. When enough phospholipids are present in the water, these bi-layered membranes naturally form themselves into the surface of a sphere, for that is their configuration of least energy: The membrane close holes that are made in it, giving up energy as bonds form among their hydrocarbon tails. The molecules can move past one another rather freely in the plane of the membrane, and thus, it is actually a two-dimensional liquid. But in order to preserve the integrity of the cell, their configuration as a closed surface in space must continue over the whole cycle of reproduction.

The proteins needed to construct plasma membranes had already evolved, since they are used to line the rigid walls of prokaryotic cells. But with rigid walls, prokaryotes are denser than water and normally sink to the bottom. They could inhabit only limited regions near the shores of the ocean. But prokaryotes would be able to float nearer the surface where they could absorb energy more easily, if they exported the proteins for managing their plasma membranes and used them to construct a large membrane. By including molecules of the right kinds within the membrane, the whole would be less dense than water, and it would open up a new habitat from which they could acquire energy to complete their cycles of reproduction.

Aquatic balloons would be, therefore, a result of the gradual evolution in the direction of natural perfection for ecologies of prokaryotes. The energy they needed was scarce near the bottom on the water, and since prokaryotes whose random variations contributed in some way to this joint control of that relevant condition would more likely be the right location to benefit from it, it would be a group-level natural selection of colonies of prokaryotes by the greater reproductive success.

The group level selection of entire ecologies also occurred, as we have seen, in the evolution of RNA. Combinations of RNA in favorable local regions were selected when storms or other disturbances came, because there would be more RNA molecules of their kinds to populate the new favorable locations. But group level selection occurs in prokaryotes because of how they cooperate in the construction of aquatic balloons in order to tap a new source of free energy.

At first, these aquatic balloons may simply have crashed when their residents had divided too many times and they grew too large. Then, new membranes would have to be constructed, and the scale of the task would require the cooperation of many prokaryotes. But this would have been possible only if their efforts were coordinated in a natural way, for example, by the rise of the sun and the increase in temperature.

Before long, however, some groups would have happened on the trick of dividing their membrane, instead of constructing a new one each morning, and could thereby stay afloat. Again, the scale of the task would require the cooperation of the many prokaryotes in each aquatic balloon, and the problem of coordination could be solved only by a regular, natural change, such as sunset and the fall in temperature. The reproductive cycles of these aquatic balloons were probably entrained, therefore, with the cycle of night and day. Once again, the circadian cycle was the mold for a reproductive cycle that only later evolved its own behavior guidance system.

Aquatic balloons would be, therefore, complex material structures with both kinds of behavior required to go through reproductive cycles, making them subject to reproductive causation. The aquatic balloons would multiply to fill the space in which reproductive cycles of this kind could be completed at all, and the resulting scarcity would impose natural selection on them. Though this would be group level natural selection relative to the prokaryotes involved, aquatic balloons would be organisms on the third level of biological organization, and as variations on the combinations of prokaryotes that made them better able to manage their membrane and coordinate their behavior completed reproductive cycles while others failed, they would become increasingly powerful in their new ecological niche. But they would not be living organisms on that biological level until they evolved a biological behavior guidance system of their own.

The nucleus. The nucleus would evolve as an improved means of coordinating their behavior. Instead of exporting the proteins from member prokaryotes, prokaryotes could have exported copies of the segments of their DNA, or genes, for handling the plasma membrane and housed them in a special membrane-enclosed chamber inside the outer membrane. It would be transformed by the gradual evolution of aquatic balloon into a nucleus that would serve as its biological behavior guidance system.

Proteins from the prokaryote’s DNA-based regulatory mechanism for selecting which segments of DNA to transcribe as mRNA could be adapted to handle strands of DNA in the nucleus. In order to synthesize proteins from these strands of DNA, however, genes for transcribing mRNA, ribosomes, and tRNA would also have to be donated to the nucleus by the prokaryotes -- as well genes for proteins that assist in replicating DNA. Since genes for proteins that divide the outer membrane would already have evolved, only minor modifications would have been required to manage a nuclear membrane as well as the outer membrane and to control the division of both so that each half of the outer membrane received one half of the divided nucleus. At first, the nucleus just assisted in managing the outer membrane, because the reproductive cycle was imposed by the cycle of night and day. But once the nucleus evolved mechanisms that enabled it to lead the whole through its cycle of reproduction, eventually even telling prokaryotic members when to divide, it would be a behavior guidance system that works on a new level of natural organization. Thus, reproductive causation once again free a new form of life from its natural mold.

Mitochondria and chloroplasts have a slightly different genetic code (that is, triplets of nucleotides determine slightly different amino acids in protein synthesis), and that might be expected on this explanation of the origin of the nucleus. Since the nucleus is a new kind of biological behavior guidance system which evolves from the cooperation of prokaryotes, it would not be surprising if rather fundamental changes occurred in the process.

Though chromosomes are on roughly the same level of natural organization as prokaryotes, it is not surprising they are much more complex than the prokaryote's loops of DNA. We should expect the nucleus to involve a complex process of molecular interactions for handling chromosomes, if the nucleus evolved from the cycle of night and day driving the cooperation of many prokaryotes through reproductive cycles. Since the nucleus was not responsible for leading the whole organism through its cycles of reproduction at first, it could start off simple and slowly acquire the complex machinery that would eventually enable it to take charge. The molecular machinery built into the cytoplasm and nucleus could be come quite elaborate, as during reproduction, when the nucleus closes up the chromosomes (in condensed form), connects them to other special molecules (and later disconnect them), moves them around in the cell, opens them up again so that its structure may flow from certain segments to protein synthesis, and much more.

Indeed, the new mechanisms of reproduction in the nucleus would be the foundation for much greater power, because the nucleus could use the condensation of chromosomes to help control which segments are exposed for transcription into mRNA during period of growth by opening up only certain parts of them. In any case, once the nucleus had taken over the function of a behavior guidance system, eukaryotes would be capable of a scale and variety of behavior that greatly exceeds prokaryotes or anything that multi-prokaryotic organisms could do. It would enable eukaryotes to establish cycles of reproduction in a much wider variety of ecological niches than prokaryotes.

This origin of the nucleus might also explain another peculiar difference between prokaryotes and eukaryotes. In eukaryotes, proteins are often synthesized from genes that are split up in several pieces of DNA separated by apparently meaningless stretches of DNA called "introns." The RNA transcribed from these meaningless segments are cut out and the meaningful segments pieced together before the mRNA are translated into proteins. This may be a new mechanism for controlling the synthesis of proteins, perhaps for synchronizing the synthesis of several different proteins.

Second origin of life. Unlike the enslavement model, this explanation of the origin of eukaryotes depends only on prokaryotes and kinds of behavior that are within their range. Living eukaryotic cells evolve from them in much the same way as living prokaryotes evolved from RNA molecules.

The key is how natural perfection at the ecological level becomes a form of group level natural selection because of how certain ecologies of prokaryotes happen on a way of taping a new source of free energy, controlling what is the most important condition affecting reproduction. The photosynthesizing prokaryotes that became chloroplasts in eukaryotic cells must have been involved in aquatic balloons from the beginning. The bacteria that became mitochondria in eukaryotes were probably also members of aquatic balloons from the outset, living in symbiosis with chloroplasts as part of the ecologies in which it happened. When they became organelles in the eukaryotes cytoplasm, both kinds of prokaryotes gave up their rigid cell walls in favor of plasma membranes.

However, if mitochondria were not members of the colony from the beginning, their presence in eukaryotic cells is not problematic, because evolving the ability to invade aquatic balloons later on to feed on the abundant supply of energy-rich molecules would have enslaved them in order to dismantle energy-rich molecules produced by chloroplasts into energy-rich molecules of a more usable kind.

The explanation of the origin of eukaryotes does, however, involves a "second origin of life" in a sense, because, once again, the cycle of reproduction was originally imposed by the cycle of night and day.

What made the origin of life inevitable was the cycle of night and day, for it drove RNA proto-organisms through reproductive cycles long enough to evolve, by way of DNA, into prokaryotes.

What made the evolution of eukaryotes inevitable was also the cycle of night and day, for it drove groups of prokaryotes, whose reproductive cycles were independent of the circadian cycle, through cycles in which a higher level organism, the aquatic balloon, was reproduced.

Furthermore, in both cases, what evolved was a higher level organism.

What evolved in one case was the DNA molecule, its regulatory mechanism, a cell and, finally, the first biological behavior guidance system able to go through reproductive cycles independent of the circadian cycle.

What evolved in the other case was the aquatic balloon, the nucleus with chromosomes, and, finally, the second biological behavior guidance system that was able to go through reproductive cycles independent of the circadian cycle.

This shows that the origin of eukaryotes was inevitable, for the only way that eukaryotic cells could fail to evolve in this way in a spatiomaterial world like ours is if there is some simpler way in which the structure of eukaryotic cells could be tried out as a variation that occurs during the gradual evolution of prokaryotes. If not, it would eventually occur as described here on any planet where life can get started at all, and thus, the eukaryotic stage of biological evolution will occur throughout the universe.

Gradual evolution. The evolution of the nucleus was the beginning of a new stage of gradual evolution in which eukaryotes change gradually in the direction of natural perfection for organisms of their kind. Ironically, the main accomplishment of that stage was the evolution of a way of incorporating the evolution of lower level structures within the eukaryotic cell. That innovation was sexual reproduction, which increased the power of reproductive causation and accelerated the pace of evolutionary change.

We have already encountered other increases in the speed of evolutionary change in tracing the overall course of evolution.

The natural selection of colonies of RNA for their combinations of kinds of RNA molecules was relatively weak at the first stage of evolution, because it depended on them having greater populations and, thus, being more likely to populate new colonies after a storm or other disturbance. But functional combinations of RNA level organisms could be naturally selected more reliably when they became genes included as segments of DNA molecules, because as DNA molecules, the combinations were more stable, and they could be tried out in a wider variety of locations.

Natural selection of RNA and DNA within colonies of molecules in favorable locations during the first and second stages was relatively weak, because the greater success of more functional RNA or DNA molecules came from being located in the colony where the proteins they synthesized had their effects. But natural selection of DNA molecules became more discriminating when they were enclosed in cells, because the fate of each DNA depended mainly on the non-reproductive structural effects that its own segments generated (rather than on the proteins synthesized by other DNA in the region).

In yet another way, even the evolution of the first biological behavior guidance system accelerated the pace of evolution, because the ability of prokaryotes to go through reproductive cycles more quickly than the circadian cycle meant that there were many more occasions for organisms to be selected by their success in reproducing.

Similar problems arose in the evolution of eukaryotes. The evolution of aquatic balloons enabled colonies of prokaryotes to focus natural selection on the combinations of prokaryotes and made them responsible for their own non-reproductive structural effects, and the evolution of the nucleus enabled aquatic balloons to go through reproductive cycles fast than the circadian cycle. But the increasing power of the eukaryote as a whole entailed a similar weakness about natural selection in eukaryotes, because the kinds of RNA-level and prokaryote-level organisms combined in the nucleus could be selected only by the natural selection of the eukaryote as a whole.

This limitation was less severe in the early in the evolution of eukaryotes, when aquatic balloons regularly disintegrated and had to be reconstructed by the prokaryotes in the region, because that meant that different combinations of prokaryotes were continually being tried out. Aquatic balloon with more functional combinations of prokaryotes would supply more members to be involved in constructing the new aquatic balloon the next day, but the mixing of prokaryotes meant that the evolution of prokaryotes with new powers in some aquatic balloons would soon be found in other aquatic balloons.

But as combinations of prokaryotes became powerful enough to maintain their aquatic balloon through many cycles of night and day, and as they came to reproduce by dividing their aquatic balloon and nucleus into two eukaryotic cells, the combinations could only be selected only by the reproductive success of entire eukaryotes. They evolved in the same way as prokaryotes, even though they were much more complex than prokaryotes and had many more random variations to try out.

Prokaryotes evolve by branchings and extinctions, so that a favorable random variation begins a whole new lineage. That lineage may exist alongside the other kinds or replace them, but other lineages cannot acquire the favorable mutation, unless their own random variations happen to try out a similar trait. This was enough for the evolution of prokaryotes, but eukaryotes were on a higher level of biological organization, and this compounding of complexity meant that reproductive causation would take much longer to approach natural perfection. And the more complex eukaryotes became, the longer gradual evolution would take.

Thus, the benefits of greater power that come with their higher level of biological organization and greater complexity tended to be lost because of the cost of slowing down the pace of gradual evolution.

Sexual reproduction. Eukaryotes solved this problem by happening on a way of accelerating the pace of gradual evolution. It was sexual reproduction, or the mixing of the structural causes bundled together in the complex material structure of eukaryotes as part of their process of reproducing.

The function for which this innovation was selected was accelerating the pace of gradual evolution. Those eukaryotes that tried it out were able to evolve faster, and thus, they were naturally selected because of their greater power.

The most obvious way of accelerating gradual evolution comes from how sexual reproduction makes it possible to combine favorable traits that evolve in different individuals. When random variations are functional in a eukaryotic cell, it does not start a new lineage by asexual reproduction, as in prokaryote evolution. Instead, sexual mixing as part of the process of reproduction makes it possible for favorable random variations that occur in different individuals in one generation to be combined in a single individual in a later generation. Thus, functional traits can be accumulated from different individuals in single individuals, combining their powers.

The sexual mixing also accelerated gradual evolution by focusing natural selection on the lower level organisms of which eukaryotes are parts. In effect, it internalized reproductive causation so that the lower level organisms of which eukaryotes are composed would gradually change in the direction of greater power in their ecological niche as parts of eukaryotes. At any point in the evolution of sexually reproducing eukaryotes, only the most powerful bundles of lower level organisms would exist, because they would be naturally selected. At that point, what makes some eukaryotes more powerful than others would depend only on differences in certain of their lower level structures, and since they would be the only parts that distinguish them after sexual reproduction, the natural selection of the whole eukaryote would turn on their contributions to the power of the eukaryote as a whole. Natural selection would be focused on different parts at different times in the gradual evolution of eukaryotes, because the powers that it is possible for them to evolve at that point would depend only on certain lower level parts and how they work together with what has already evolved to control relevant conditions. Thus, as natural selection shifted from one part of the eukaryotic structure to another, eukaryotes would become increasingly powerful.

The mechanism of sexual mixing means that natural selection can be focused on structural causes at both levels of biological organization below eukaryotes. The shuffling of chromosomes from different parents in the process of reproduction tries out different combinations of DNA level structural causes, and that was probably the original form of this mechanism, because the nucleus had evolved as a mechanism for handling whole chromosomes.

But eukaryotes also evolved a way of extending this effect to the RNA level structural causes of which prokaryotes are composed, that is genes. "Crossing over," as it is called, is a process in which segments of the paired chromosomes from different parent are recombined before being separated from one another and bestowed on different cells. Thus, sexual mixing affects the combinations of units of behavior that make up eukaryotic behavior at both lower levels of biological organization.

Furthermore, the shuffling of chromosomes (and crossing over between them) meant that a far wider range of random variations would be tried out by each generation.

Finally, when eukaryotes evolved the trait of carrying two copies of each chromosome (diploidy), it was possible to preserve genes that might turn out to be useful later or in different combinations with other genes.

The advantages of sexual reproduction are general and would have accelerated the evolution of prokaryotes as well as eukaryotes. But the rigid cell walls of prokaryotes made it difficult for sexual mixing of DNA to be a regular part of reproduction, whereas it was relatively easy for eukaryotes.

In eukaryotes, the self-forming nature of plasma membranes made it relatively easy to mix parts of their DNA, because that enabled different eukaryotes to merge into a single cell. Moreover, from the beginning, in order to reproduce at all, the eukaryote had to replicate each chromosome in its nucleus, separate the copies, divide its nucleus, and bestow one copy of each chromosome on the nucleus of each half of its dividing outer cell (mitosis). Since it already had mechanisms for handling multiple chromosomes and putting them in the nuclear plasma membranes it constructed, the eukaryote could evolve a mechanism that would shuffle the chromosomes from different cells when they merged, separate chromosomes of the same kind from one another, and bestow a nucleus with one complete set on each half of the dividing cell. This second way of dividing of dividing the cell (meiosis) would account for the various patterns of sexual reproduction found in extant eukaryotes.

To be sure, bacteria, such as E. coli, have a process, called conjugation, which accomplishes much the same thing, although it is not part of reproduction. These prokaryotes construct a cytoplasmic bridge between them and exchange segments of DNA, called “plastids.”

But conjugation is not common in prokaryotes, and it may reflect the selection pressures of being confined to the digestive tracks of multicellular animals. Conjugation enables E. coli to share the mutations by which they can consume new kinds of energy-rich molecules, which stem from changes in the animal's diet. Not only were their non-conjugating cousins not selected, but neither could the animals that lacked conjugating E. coli survive when radical changes in diet were required.

Life began about 3.5 billion years ago, less than a billion years after the formation of the planet, and eukaryotes evolved between one and two billion years ago. But the evolution of sexual mixing during reproduction would explain why evolution has taken less time to reach its present state than it took for prokaryotes to evolve into eukaryotes.

Species. Another dramatic effect of sexual reproduction on the nature of the ontological cause of evolutionary change was to advent of true species. The ability to mix genes sexually with one another makes eukaryotes members of a species that share a common gene pool. Since parts of their complex material structures from the lowest level of biological organization (the RNA level) are regularly mixed in constructing new organisms, there is a sense in which what is evolving is not the organisms, but the gene pool species. The gene pool is just all the genes in the particular organisms that are capable of sexual reproduction and, thus, make up the species.

This does not mean, however, that the gene is the “unit of selection,” as many contemporary Darwinists would have it. The unit of selection is determined by the ontological cause of gradual evolution, or the reproductive cycle, and that depends on the whole organism. The whole reproducing organism is what is naturally selected, because that is the complex material structure that does all the non-reproductive work, the structure that is reproduced, and the structure whose reproduction imposes natural selection on itself.

When the individual organisms are mixing their genes sexually, however, what makes some individuals more powerful than others at any point in their evolution usually comes down to a few genes that are responsible for the differences between their traits at that point. Natural selection is focused on those genes because they affect the reproductive success of the organisms. But that does not mean that the gene is the “unit of selection.” That is just an appearance, which is due to the way in which sexual reproduction makes reproductive causation more efficient. Though the sexual mixing of genes during reproduction has the effect of focusing natural selection on the genes, it is still the reproducing organisms that are being selected by their success in reproduction. And the frequency of genes in the gene pool is merely a useful way of describing the change taking place in the evolution of species by the natural selection of reproducing organisms

Indeed, in organisms that can reproduce only sexually, the unit of selection is not the individual organism, but a larger unit, the mating pair. The individual organism is not a complete bundle of the structural causes that is going through reproductive cycles; it not the material structure that is responsible for the reproductive cycle. Since only a pair of organisms can reproduce, each individual is just half of the material structure that is responsible for the whole cycle of reproduction. Each individual organism must seek its other half in order to be complete. What obscures the unit of selection is that the other half of the reproducing organism is not determined until mating actually occurs.

Even in organisms that can reproduce asexually, the mating pair is a unit of selection, because as long as they can reproduce sexually, that will involve a much more efficient form of natural selection and the mating pair will be the organism that is responsible for the reproductive cycles that constitute gradual evolution.

Eukaryotes drop sexual reproduction only when they occupy stable ecological niches in which they have already reached maximum holistic power for organisms of their kind. But if the environment were to change, closely related species that still reproduce sexually would adapt faster and replace them.

Furthermore, with the evolution of multicellular animals, the unit of selection is sometimes even more inclusive, because multicellular organization enables generations to live side by side.

In protists, or single-celled eukaryotes, sexual reproduction means death to the individual organism, because individual organisms must merge with one another in order to mix their genes in the process. But multicellular organisms do not need to die in order to reproduce. They can set aside special cells for that function, because multicellular organisms reproduce, as we shall see, from a fertilize egg cell. The multicellular organism can, therefore, live side by side with their offspring after reproducing.

Many kinds of animals take advantage of this fact to control more of the conditions affecting their reproduction, for example, by caring for their offspring. Thus, their offspring may go through periods when they are unable to fend for themselves before they take on the adult role of parents themselves. To the extent that a species comes to depend on this generational overlap, the reproducing organism may include not only the parents, but also their offspring, that is, the whole family. In that case, the unit of selection is the multi-generational entity, or “composite organism,” that includes, at least, periods during the cycle when two (or more) generations live side by side and do the non-reproductive work of controlling conditions that affect the reproduction of them all.

In addition to parental behavior that nurtures and protects offspring, the traits that may evolve because of this larger unit of selection include behavior in the offspring that contributes to the maximum holistic power of the composite reproducing organism, such as dispositions to follow parents and altruism toward other parts of their composite organism. This accounts, I would argue, for what is called "kin selection", which will be discussed later.

There are, as we shall see, even larger units of selection, if evolution is due to reproductive causation. But the cause is not the sexual nature of reproduction. It is group-level selection, and it may cause the evolution of composite organisms at the same time mating pairs and families are evolving by their natural selection.

4. Multicellular stage: embryological development. Higher levels of part-whole complexity in the structure of organisms are ontological causes of stages of evolution, and we have seen how three levels of biological organization are responsible for three stages of evolution (molecular, prokaryotic, and eukaryotic). It is obvious that there is a higher level of part-whole complexity than single-celled eukaryotes, for there are organisms composed of eukaryotic cells that are simply attached to one another. And a new stage of evolution does seem to have been caused by the appearance of one kind of multicellular organism, at least, for the Cambrian revolution some 600 million years ago, which is virtually the beginning of the fossil record, is the first evidence of multicellular animals.

In order to prove the inevitability of another stage of evolution, however, we must show that a higher level of biological organization is both possible and can bring an entire new range of conditions affecting reproduction under control. Once again, the function of a higher level of part-whole complexity is obvious, because organisms are larger on the multicellular level and they can deploy the behavior of whole armies of lower level organisms. But it not so obvious how it is possible, because the capacity to coordinate the behavior of lower level organisms is more than simply bundling them together as parts of a higher level organism. It requires the capacity to coordinate their behavior (including their reproduction) to do non-reproductive work. As in the eukaryotic stage, therefore, the main challenge at the multicellular stage of evolution is showing the possibility of a biological behavior guidance system on a higher level of part-whole complexity.

Multicellular animals, rather than plants, will be our main focus, because they begin the series of evolutionary stages that lead up to beings like us. We shall focus, therefore, on the mechanism of embryological development in multicellular animals and even trace its origin. But then, in order to law the foundation for tracing the neurological stages of evolution in multicellular animals, we shall draw back and consider animals more generally, both the basic nature of animals and all the possible kinds of animals, basic and anomalous.

The possibility of multicellular animals. In order for organisms to evolve at the multicellular level, it must be possible for complex material structures to do both kinds of work required to go through reproductive cycles. One kind of work is reproduction, and at the previous levels, the higher level organism was able to reproduce by coordinating the reproduction of the lower level organisms of which it was part. But that is not possible at the multicellular level of biological organization, at least, not in animals in which the pace of evolution depends on sexual reproduction.

Prokaryotes reproduce by replicating all the genes on their loop of DNA, and eukaryotes reproduce by replicating their chromosomes (and self-reproducing organelles in the cytoplasm). But what makes that possible is their biological behavior guidance system. In both cases, it is possible to coordinate the behavior of the lower level organisms, because the lower level organisms are parts of the biological behavior guidance system and they contribute to the behavior of the organism as a whole by how they move and interact within that more inclusive structure.

Multicellular organisms, by contrast, are just eukaryotic cells attached to one another, and since each contains all the structural causes of its own behavior, they would never be anything more than just colonies of eukaryotic cells, if multicellular organisms reproduced only by each of the cells reproducing itself. They could evolve such cooperative behavior by group level natural selection, but it would be very inefficient, like the evolution of RNA at the molecular stage and the colonies of prokaryotes from which eukaryotes evolved. What they need is a biological behavior guidance system to coordinate their behavior. But anything like the nucleus in eukaryotes or even the cell-enclosed loop of DNA in prokaryotes would be far too cumbersome. And even if it were possible, it would either have to give up the advantages of sexual reproduction or evolve a new way of sexually mixing the structures of its lower level organisms in the process of reproducing on the multicellular level.

What makes it possible for multicellular organisms to have a biological behavior guidance system is that the cells of which it is composed can all be generated by the asexual reproduction of a single cell. And since it is generated from a single cell, multicellular organisms can evolve in the efficient way made possible by the sexual mixing of the lower level organisms of which they are composed, because the cell from which they are constructed can be a fertilized egg cell derived from different multicellular organisms in the previous generation.

At the multicellular level, in other words, the biological behavior guidance system is originally located within a single eukaryotic cell, and it is able to coordinate the behavior of all the eukaryotic cells making up the multicellular organisms because they are all its offspring and their behavior is coordinated from the beginning of their lives. This is what I will call the “mechanism of embryological development.”

Since the behavior of the eukaryotic cell is guided by the nucleus, this coordinating mechanism must be a modification of the nucleus. The plan for the behavior of every kind of cell in the mature multicellular organism must be contained among the chromosomes in the nucleus, and thus, a copy of the entire multicellular plan is bestowed on each daughter cell. But in order for each cell to generate its distinctive behavior, it must express only some of the genes on certain chromosomes, and that means that each cell must be able somehow to identify itself with one kind of cell in that plan, for otherwise the entire genetic plan would not affect different cells differently. A rather major modification of the nucleus is required to make the chromosomes in each cell express their genes in a way that is distinctive for cells of its kind, and it works only because the cells all come into existence in a unique way as offspring of the original fertilized egg cell

The mechanism of embryological development. The mechanisms of embryological development are only now being discovered, but in multicellular animals, at least, it must enable the nucleus of different kinds of cells to operate in basically different ways. Though such a mechanism is not problematic in the case of plants, animals need a more complex multicellular structure and that does pose a problem.

It is not difficult to see how plants could have evolved from single-celled eukaryotes. The mechanism responsible for constructing their multicellular organization is a simple variation on the eukaryotic behavior guidance system, which can reproduce asexually as well as sexually. In this case, daughter cells from the asexual reproduction of an original cell remain attached to one another and cells differentiate according to a gradient of messenger proteins (hormones) maintained throughout their extra-nuclear cytoplasms. Even a two-cell organism would be an advantage in completing a reproductive cycle, if one cell attached itself to the ground while the other grew out from it toward the sun. Not much of a change is required to establish a gradient from one end of the composite whole to the other, since single eukaryotic cell can already respond to molecules in the environment and orient themselves to electromagnetic radiation. What is required is a mechanism that would use the gradient of to open up the chromosomes of difference cells in different ways. Moreover, once it evolved, reproductive causation could easily come up with more complex plants, because during the whole process of development, the cells can be acquiring energy from photons. A complex process could evolve by adding step to a simpler process. In fact, plants probably evolved from plant-like protists many different times. For example, the spherical colonies of plant-like protists that float in the water (the Volvox series) appear to have evolved independently of plants that attach themselves to the ground with a holdfast.

There is, however, something quite puzzling about the evolution of multicellular animals, at least, in those that become most powerful, because they have bodies that are complex enough to require a nervous system to guide them. Their process of embryological development can also use gradients of messenger molecules to give cells different kinds of behavior, but something more is needed in the case of multicellular animals, because in order to set up a complex body, masses of cells (or even individual cells) must move in relation to one another in a regular pattern. Daughter cells cannot remain attached to one another in a fixed spatial relation.

Animals evolve from cells that are, unlike plant-like protists, capable of locomotion, and thus, coordinating them can involve coordinating their locomotion as well as other kinds of behavior. That means that the multicellular biological behavior guidance system in animals must be able to alter certain cells and their daughter cells early in the process so that, subsequently, they behave in ways that do not depend solely on the messenger molecules in the neighborhood (and can determine other cells they encounter to become cells of a specific kind as well). Once the structure of multicellular body is set up, the behavior of all the cells can be coordinated by the distribution of messenger molecules (hormones) throughout the body, because they will have different effects on different kinds of cells.

Moreover, embryological development in animals is not only more complex than in plants, but it is also quite puzzling how it could have evolved in the first place, because animals cannot acquire energy for themselves until the body is formed and they are able to ingest other living objects. The entire process of embryological development must be set up in advance with an adequate supply of energy in a fertilized egg, and the problem is how such an elaborate process could have been tried out as a variation during the gradual evolution of animal-like protists.

Such an elaborate coordination of animal-like protists cannot be simply an adaptation of the eukaryotic biological behavior guidance system, but requires a new structure in the fertilized egg cell that can construct a multicellular animal body from its offspring and coordinate their behavior. Such a process could be generated as a structural global regularity with just a few mechanisms.

There is evidence that what determines a cell to certain kinds of behavior rather than others are "homeobox genes", or master genes that activate or repress the expression of subordinate genes on nearby segments of their chromosomes.

And it is possible to alter cells (that is, “determine” cells) so that even their offspring have special kinds of behavior. For example, if what controls which segments (and, thus, which homeobox genes) are opened up were a self-forming complex of protein molecules that becomes attached to the DNA molecule at certain points, they could be reproduced when the cell reproduces, because one half of the protein complex could remain attached to each of the strands of DNA being copied so that subsequently, after it had synthesized its complementary strand of DNA, each half of the protein complex could attract the other half of the self-forming complex. Thus, daughter cells would have protein markers attached to its chromosomes that make them behave differently.

It is possible for the fertilized egg cell to determine its daughter cells at the very beginning so that they act, thereafter, in basically different ways from one another, independently of the hormones that they may encounter, because different daughter cells inherit different parts of its cytoplasm. If different messenger molecules were located in different parts of the fertilized egg cell, they would wind up in different groups of cells after the first few divisions, and the process of embryological development would begin with different groups of daughter cells having basically different kinds of behavior, including locomotion relative to one another.

Even though a multicellular animal is, at one point in its reproductive cycle, just a single cell (a fertilized egg cell), it must be counted as a higher level organism, because that cell is the structural cause of embryological development. Embryological development is a complex structural global regularity whose outcome is a complex organization of various kinds of cells in which the behavior of the cells is coordinated by the exchange of messenger molecules. And since the complex material structure responsible for this global regularity goes through reproductive cycles with both essential kinds of behavior, it evolves by reproductive causation toward natural perfection for organisms of its kind.

To be sure, multicellular animals are different from prokaryotes and eukaryotes. Prokaryotes and eukaryotes have the same level of organization throughout their reproductive cycles, whereas multicellular animals have a period during which they are at the eukaryotic level of biological organization. But that merely reflects the nature of their biological behavior guidance systems. In prokaryotes and eukaryotes, the biological behavior guidance system is the an aspect of the structure of their highest level of biological organization, whereas in multicellular animals, the basic structural cause is located in a single cell, the fertilized egg cell. But since it is clearly the structural cause of a multicellular organism, there is no reason to doubt that it is on a higher level of biological organization.

Levels of biological organization are basically levels of part-whole complexity in space, but as we have seen, they also typically involve levels of part-whole complexity in time. That is, a single reproductive cycle at the higher level may include many reproductive cycles of the lower level organisms of which they are composed. Prokaryotes and eukaryotes both use many cycles of the RNA molecule’s reproduction in doing their non-reproductive work, because it depends on transcribing segments of the their DNA as mRNA and then using them to guide protein synthesis. And in eukaryotes, mitochondria and chloroplasts may go through many reproductive cycles during a single reproductive cycle of the cell as a whole. In addition to incorporating lower level reproductive cycles, a single reproductive cycle of a multicellular animal uses many eukaryotes reproductive cycles to construct a multicellular body. The main difference is that multicellular animals use many cycle of the reproduction of the lower level organisms not only to do non-reproductive work, but also to reproduce themselves. But that is not a reason for doubting that they are on the multicellular level of biological organization.

These general points about its nature show how a new kind of biological behavior guidance system is possible, in principle, at the multicellular level. That is, there is little reason to doubt that the mechanism of embryological development would eventually be tried out as a random variation during the evolution of eukaryotes. Since the greater power of multicellular animals is hardly in doubt, we can conclude that the multicellular stage of evolution was inevitable.

The section at the end of this chapter uses what is known about the simplest multicellular animals on earth to explain how the origin of the mechanism of embryological development can be traced to single-celled eukaryotes.

Animals. Though the evolution of multicellular plants may also involve a series of stages, nothing more will be said about them here, because the current project is to show that there is a series of inevitable evolutionary stages leading up to rational beings like us (and beyond). The evolution of multicellular plants is a separate branch of evolution. But to lay the foundation for tracing the evolution of animals through a series of inevitable stages to rational beings like us, let us first consider the basic nature of animals and inventory the kinds of animals that can evolve, both basic and anomalous.

That will leave us to consider, in subsequent chapters, the differences among animals that depend on in levels of neurological organization at the multicellular stage. The social level of biological organization will be introduced by way of insect colonies, for they are an example of the anomalous animal that will be explained in this catalogue. Though human society is also an animal on the social level, it depends on the stages of animal evolution caused by levels of neurological organization, and thus, there is not much to say about it until after we trace the stages of animal evolution.

The Nature of Animals. The difference between animals and plants (and plant-like organisms) is part of the differentiation of organisms into kinds that occurs at each stage of biological evolution. What makes animals different from plants is not their level of part-whole complexity, but that animals acquire the free energy (and parts) they need to fuel their reproductive cycles by ingesting other objects in space. Those objects are not mere photons, but material objects, with rest mass — sometimes just energy-rich molecules, but usually other organisms.

Animals require, therefore, a kind of behavior that is radically different from anything plants require. In order to ingest other objects in space, animals must have a kind of behavior that acts on them, whereas plants (and plant-like organisms) need only behavior that acts on the world as a whole at the moment. Though plants often need to orient their bodies and their behavior in the world, they act, at most, only in some direction relative to a field in space, such as gravitation, in the direction of electromagnetic radiation, or relative to gradients of water in the soil, the magnetic field, and the flow of air or water. Such behavior is not directed toward particular objects in space, but merely affects whatever objects may be located in the direction in which its behavior is oriented. By contrast, no animal, regardless how simple, could not control even the most basic condition that affects its reproduction as an animal, unless it could direct its behavior toward particular objects in space. Thus, we might say that, whereas plant behavior acts on the whole world at the moment (or, at most, some direction in space), animal behavior acts on objects in space.

A new system is required to guide the animal’s special kind of behavior, because ingesting other objects is a hazardous way of making a living. Ingestion is an intimate way of relating to another objects, and since there are usually many kinds of objects around that would harm the animal, if ingested, animals must have a mechanism of some kind by which to tell in advance which objects to ingest and which to pass up. Eating and not eating are incompatible behaviors with respect to any given object in space, and selecting which objects to eat is, therefore, a condition of the existence of reproductive cycles fueled in this way. Such a basic function may well be called a "need," and thus, needs, like functions, can be used to explain the traits that evolve.

That is, there are various ways of doing non-reproductive work within the range of random variations being tied out, and those that make it possible for organisms to acquire energy as animals do will be selected by their power to control that relevant condition. Thus, reproductive causation implies that organisms with animal behavior guidance systems will evolve, if they are possible.

The animal behavior guidance system is a second system for guiding behavior in most animals, because as living organisms, animals already have a system that selects between incompatible kinds of behavior, namely, the biological behavior guidance system. Such a mechanism is needed to coordinate the behavior of the lower level organisms that are bundled together as the higher level organism, and it is responsible for guiding the organism’ through its reproductive cycle.

The first such biological behavior guidance system was at the prokaryotic level. It was necessary, as we have seen, because the two kinds of work that the first organisms had to perform during each cycle in order to evolve, growth and reproduction, were incompatible and could not be generated at the same time. Its origin during the prokaryotic stage marked the beginning of life, since the ability to select and generate both kinds of behavior is what enabled organisms to go through reproductive cycles on their own, independently of the cycle of night and day. That gave them the autonomous activity ordinarily meant by saying that something is alive, and as living organisms, that make themselves evolve.

At each subsequent stage of biological organization, a new biological behavior guidance system was needed, because it was necessary to coordinate the behavior of the new kind of lower level organisms that are bundled together and go through reproductive cycles as a whole. Since, at any biological level, animals already have a biological behavior guidance system, and he animal behavior guidance system is their second system for guiding behavior, one whose function is to guide the special kind of behavior that animals need in order to acquire free energy by ingesting other material objects in space.

The reason for calling both mechanisms "behavior guidance systems" is that they similar kinds of functions. In both cases, a basic choice must be made between incompatible kinds of behavior in order for organism of their kind to go through reproductive cycles at all. For organisms to be alive, it is the choice between growing and reproducing, whereas for living organisms to be animals, it is the choice between eating a particular object and not. There is no way to avoid making such a choice in either case, for the two essential kinds of behavior cannot be generated at the same time. (It is less inconvenient in multicellular organisms, with their unique way of reproducing, because this choice is made when cells are determined to have different functions and some are assigned the task of reproducing the organism as a whole.) Since the biological and animal behavior guidance systems evolve to serve similar functions, we can discern a basic similarity in their structures, because they must serve similar subfunctions.

A behavior guidance system is not a mere cybernetic device, as we have seen. Cybernetic systems use feedback from the consequence of their behavior to attain or maintain some overarching goal. But behavior guidance systems are essentially different, because their function is to select between incompatible goals. The difference can be seen in how the behavior guiding function requires mechanisms to serve no less than three sub-functions, regarding input, selection and output.

Input. In order to make the selection among possible goals, input is required about the current state of affairs, either about the world as a whole or about particular objects in space. That means that the system must be affected by the state of the world (including, perhaps, the state of the organism itself) in a special way when choosing one of the alternatives or the other would control the condition that affects reproduction.

Selection. The input must change a state of the behavior guidance system in some way so that the system selects the right goal from the alternatives, which is its basic function. This is the sub-function that a cybernetic system lacks.

Output. In order for its selection to make a difference, the behavior guidance system must also be able to generate the appropriate kind of behavior. Since it is directed at a goal, such output typically has the structure of a cybernetic system, using feedback from the effects of earlier behavior to adjust its output to attain the chosen goal.

Thus, the behavior guidance system's three essential sub-functions are receiving input, selecting the goal, and generating output (which may also use input as feedback). It cannot get by with fewer sub-functions, whereas the cybernetic system, with a fixed goal, requires only a mechanism for registering input and generating behavior accordingly.

The nature of reproductive causation entails, as we have seen, that non-reproductive work is not a means to reproduction as an end in the biological behavior guidance system. The goals of non-reproductive work are the conditions affecting reproduction that must be controlled, whereas reproduction is merely the cause of the natural selection by which they evolve.

Animal behavior itself is different from the kinds of behavior guided by the biological behavior guidance system, because it must be directed at other objects in space, not merely at the world as a whole (including orientation in a field of some kind). The spatial aspect of animal behavior may not be obvious in some cases. It can be just an aspect of the unchanging structure of the animal body as, for example, in sedentary animals that filter the flow of water to feed on smaller organisms. But the spatial aspect is essential, because the free energy that animals use is contained in objects that have locations in space. Those objects must be ingested, and in order for animals to become more powerful, they must acquire traits that take advantage of how their sources of free energy are located in space.

Though the behavior guided by biological system is not directed at any other particular objects in space, but only at the world as a whole, it can still gradually evolve greater power, because it can organize different kinds of behavior in time. As we have seen, the biological behavior guidance system is a higher level structural cause that coordinates the behavior of the many lower level organisms of which it is composed, and it is responsible for all the behavior required to complete a whole reproductive cycle, including both growth and reproduction. Such a complex material structure is what made it possible to explain gradual evolution as a global regularity that is caused ontological by reproductive cycles and the wholeness of space.

Though the cycle of reproduction does not exist fully at each moment, its structural cause does, and since the entire cycle is implicit in a material structure (that is, its biological behavior guidance system) which does exist fully at each moment, the ontological cause of gradual evolution could be described, paradoxically, as a four dimensional object that endures through time and reproduces in space. Thus, implicitly contained in the structure of the biological behavior guidance system are not only both the phases of growth and reproduction, but all the responses to changing circumstances and sequences of behaviors using feedback to attain goals that occur during the entire reproductive cycle.

It may be surprising that nothing but the right sequence of activities at the right times is needed to generate a whole reproductive cycle (except, perhaps, for orienting itself in various fields). But taking advantage of the power to sequence behavior temporally is what enables the biological behavior guidance system to become increasingly powerful at each stage of evolution. In addition to making each behavior as effective as possible in controlling its relevant condition, reproductive causation inserts or deletes kinds of behavior from temporal sequences, changes their duration or quantities, and rearranges their sequences in time. The right sequence (conditioned on relevant input) can be very powerful. That is why the biological behavior guidance system is the locus of most evolutionary changes in such organisms.

This difference between animal and merely biological behavior is ontologically basic, because in addition to any temporal sequencing of behavior that is generated by the biological behavior guidance system, the animal behavior guidance system also imposes a spatial structure on the behavior of the organism by acting on other objects in space. Insofar as the power of the animal behavior guidance system to control what happens increases by taking advantage of the fact that the objects containing free energy have locations in space, animal behavior is superimposing a geometrical structure on the region.

Organisms can evolve only in regions where there is a supply of free energy, and as we have seen, there is a region-wise geometrical structure about the thermodynamic flow of matter from potential energy through kinetic energy (and radiation) toward evenly distributed heat that constitute free (or usable) energy. Thus, we can see animal behavior as channeling the thermo­dynamics flow in the region. In other words, what most material structures do simply by existing in the region, animals do by acting on objects in space. That is what makes animals more powerful than plants, and it suggests how far animals might evolve in the power to control relevant conditions.

Structural causes generate irreversible structural global regularities by using free energy to do work, that is, making things happen that would not otherwise happen. Though animals are just organisms contained along with other objects in the region, the evolution of behavior that takes into account the locations of other objects in space in order to control conditions that affect their behavior can channel the flow of free energy toward increasing entropy over very large regions of space. In other words, the spatial aspect of animal behavior (being directed at objects in space) imposes a geometrical structure on the region (and, thereby, channels the thermo­dynamic flow in the region in a way that would otherwise require a material structure as large as the relevant region, like a giant machine or building). The actualization of the potential of animal behavior to do work in the region is what we are tracing by deriving from spatiomaterialism the evolutionary stages that determine the overall course of evolution.

This potential is actualized mainly in multicellular animals because of the evolution of a series of level of neurological organization in them, but before we trace those stages, let us catalogues all the other animals to see how multicellular animals are related to all the other kinds of animals.

Kinds of animals. Stepping back from the multicellular level of biological organization, this explanation of the nature of animals entails a classification of animals into their natural kinds. The basic kinds of animals are easy to classify, because they are ontologically necessary, and identifying them will provide a map of subsequent stages. However, this way of sorting out the basic kinds of animals resolves several puzzles about the classification of animals in biology, and thus, we will conclude with a survey of the kinds of anomalous animals that are just as ontologically necessary.

Basic kinds of animals. Since animal behavior guidance systems evolve at each level, the most basic divisions among animals correspond to the levels of part-whole complexity in the biological behavior guidance system discussed in the last section. We should expect some kinds of animals at each level of biological organization, because animals are just a variety of the living objects that evolved at each stage of evolution. They are, in technical terms, heterotrophs, which acquire the free energy to fuel their structural effects from objects with a rest mass where energy is stored in their chemical bonds. Plants, by contrast, are autotrophs, which acquire energy directly from the sun by absorbing photons.

At the prokaryotic level of biological organization, the heterotrophs are bacteria. They feed on energy-rich molecules, and their varieties mirror the kinds of molecules they consume.

The animal behavior guidance system at this level need not be very complex. It is a molecular structure in the cell wall that can identify the right kinds of molecules and draw them through the cell wall into the cell to be dismantled inside while keeping dangerous (and useless) molecules outside.

To be sure, autotrophs at this level, such as cyanobacteria, also consume molecules, but only for use as parts in growing (or as input signals), not as a source of free energy. Parts can be acquired without an animal behavior guidance system, because the simplest, energy-poor molecules, which are almost always available as part of the medium both inside and outside the cell and pose no danger, can be used as parts. But animals need a special system in order to ingest large, energy rich molecules, for that poses a hazard.

At the eukaryotic level of biological organization, the heterotrophs are animal-like protists, or single-celled eukaryotes. They feed mainly on prokaryotes and plant-like protists (algae). But there are several new animal behavior guidance systems, and to suggest their range, let me mention three kinds.

The paramecium has a stiffened cell membrane with an oral groove along one side in which many hair-like cilia sweep small particles into a mouth, where they are enclosed in a vacuole for digestion inside the cell — unless they are harmful and they are kept out. This animal behavior guidance system is clearly independent of the biological behavior guidance system, the nucleus, for when the nucleus is removed, a paramecium continues moving and feeding for many days.

Amoebas have a soft plasma membrane, instead of the stiffened cell membrane that gives paramecia their shape, and amoebas move along the substratum by constructing an extension of the plasma membranes on one side of the body while dismantling it on the other (pseudopodia). Amoebas ingest prokaryotes, algae, and even small animal like protists by wrapping part of their outer membrane around the energy-rich object and then enclosing the package within its cytoplasm as a food vacuole where digestion takes place. Hence, their choice about feeding is made locally in the course of moving about.

Finally, collar flagellates remain attached to the substratum and use the whip-like motion of their flagellum to pull microorganisms to a region near a collar at the base of the flagellum where they can be ingested.

There is one kind of protist, Euglena, whose identity as plant or animal is in doubt, because these flagellates have chloroplasts for acquiring energy from photons and yet also ingest prokaryotes. However, they may be plants, rather than animals, because they probably use their prokaryotic prey for their nutrients, rather than for energy, since what is scarce near the surface of the ocean which they inhabit are heavier atoms. (This is the kind of scarcity that accounts for animal-like multicellular flowers in rain forests, such as the Venus fly-trap, that ingest animals. But since the objects are ingested for parts, rather than energy, they are not animals by this definition.)

The multicellular level of biological organization makes possible the most powerful ways of guiding animal behavior, because it uses multiple neurons. Neurons are cells whose structure enables them to transmit signals from one place in the body to another or among themselves, and since neurons are capable of being organized at a series of levels of part-whole complexity, there are differences among kinds of multicellular animals that are nearly as basic as these differences among other kinds of animals.

Multicellular animals direct behavior at other objects by the contraction of muscle cells located where the muscles are needed to change the body’s shape, and neurons generate behavior by controlling the relevant muscles. But behavior must depend on input from the other objects in space in order for animals to choose how to behave towards them and to generate behavior whose spatial aspects will control the outcome of interacting with them, and so neurons must be connected to sensory receptors on which other objects in space have an effect. The choice of kind of behavior depends on the “interneurons” connecting sensory neurons on the input side and motor neurons on the output side (usually in conjunction with input about the state of the body itself concerning its energy needs, mating urges, damage to cells, and the like).

The behavior of the neuron itself is generated, as in all machines, by the geometrical structure of such material objects and how they structure the flow of free energy toward entropy increase in their region. In the neuron, molecular mechanisms in the plasma membrane control of the passage of sodium and potassium ions through its plasma membrane in such a way that an action potential propagates along the axon of the neuron, and that affects the passage of small proteins, called “neurotransmitters,” at the synapses where they meet determines whether a signal is passed on. But the details of the neuron's mechanism are well known and not relevant here.

What is relevant is how they constitute an animal behavior guidance system. Any behavior guidance system, given its function of selecting between incompatible kinds of behavior, must have systems serving three basic sub-functions, and in those that are made of neurons, they will be called the sensory input system, the goal selection system and the behavioral output system.

Among animals with nervous systems, the most basic classification has to do with the level of part-whole complexity in the systems serving the three basic sub-functions. The animal behavior guidance system imposes a geometrical order on the region by how it moves its body around and acts on other objects in space, and there are higher levels of neurological organization in multicellular animals, because they are possible and each actualizes further the power that animals can have by taking spatial aspects of the objects on which they act into account in guiding their behavior in relation to them. The levels of part-whole complexity occur in the three basic systems making up the animal behavior guidance system, and given the ontological explanation of revolutionary evolution, they lead, as we shall see below, to three additional stages of evolution in multicellular animals. Somatosensory animals are the first animals to evolve at the multicellular level, and three additional stages occur because of levels of neurological organization: telesensory (most invertebrates and non-mammalian vertebrates), subjective (mammals), and manipulative (primates).

At the social level of biological organization, there are two basically different kinds of animals, only one of which has a new kind of animal behavior guidance system that is possible only at the social level. That is the spiritual animal, which is made up of primates as its lower level organism. The same behavior guidance system serves as both its biological and animal behavior guidance system, because the behavior of many individual primates is coordinated so that the spiritual animal acts as a whole by the use of language. The capacity to use language depends on the evolution of additional levels of neurological organization, which determines a series of stages of evolution (though, as we shall see, the last level does not require any change in the biologically inherited structure of the nervous system).

Primitive spiritual animals are groups of primates with the capacity to use a language of natural sentences (that is, sentences with a simple subject-predicate grammar). The linguistic level of neurological organization comes from a higher level of part-whole complexity within the primate faculty of imagination in the so-called “left brain” which enables it to combine the meanings of words as propositions and to indicate the structure of the covert linguistic act involved by verbal behavior (by words and grammatical markers).

Rational spiritual animals are also animals at the social level of biological organization, but they have the capacity to use psychological sentences (that is, sentences with predicates formed of verbs of propositional attitude, such as “believes” and “desires,” together with complete sentences). This linguistic capacity enables the users of language able to think about the causes of their behavior and belief as part of the process of causing them, and so it will called the reflective level of neurological organization. Reflection makes it possible for language to guide individual level and social level behavior in a new way, which involves rational imagination and enables them to understand arguments, and that is the foundation for a new form of evolution by reproductive causation, namely, cultural evolution.

Philosophical spiritual animals are social level animals in which culture has evolved a new level of argument, in which all the arguments of the rational level are organized as parts of a single argument. That is a means of proving that propositions are necessarily true, and thus, it is a new way of discovering the true and the good. Though this is a stage of cultural evolution, it gives the members of the spiritual animals in which it exists a higher level of rational imagination, and thus, it is also the philosophical level of neurological organization. But there are, as we have seen, two ways of constructing such philosophical arguments, epistemological and ontological, and only one of them is able to succeed.

This classification of animals identifies most of the natural kinds, but there is another kind of animal it leaves out. It may be represented by the other kind of animal at the social level of biological organization, or multisomatic animals, such as insect colonies. They have long posed a puzzle for zoologists, because it is not obvious how to classify them. They are social and, thus, like human society, and yet they are so different. But insect colonies are only one of a number of animals that have defied classification, and this ontological explanation of evolution, including both gradual evolution and revolutionary evolution, offers a solution. Thus, we may use the way in which it solve the problem of anomalous animals as a further reason to believe that it is true, before we take up the structure of the nervous system and explain how it works in detail.

Anomalous Kinds of Animals. There is another way that the animal behavior guidance system combines with the levels of biological organization to account for species as natural kinds. Thus far, animals have been classified according to the new kind of animal behavior guidance system made possible by each biological level — as bacteria, animal-like protists, and animals with nervous systems, and spiritual animals. But the same elements can be used to explain the various anomalous kinds of animals.

It requires only that we notice that organisms with the new kind of animal behavior guidance system made possible by one biological level can also be organized merely as so many lower level organisms bundled together as a higher level animal organism. Though it does not have the new kind of animal behavior guidance system made possible by its own level of biological organization, it is still an animal, because it is a heterotroph. Its only animal behavior guidance system is the kind that evolved at the lower level of biological organization. And it has many of them, one in each of its parts.

The most obvious example is the sponge. Sponges are multicellular organisms. And they are animals, acquiring energy from energy-rich objects. But unlike other multicellular animals, they lack a nervous system. The reason is that the sponge is just an organization of collar flagellates, each with an animal behavior guidance system of a kind that evolved in collar flagellates on the eukaryotic level, but put together as a multicellular organism. These animal .like protists are configured like a jar; their flagellums pull water through pores in its side and push it out an opening at the top. Each cell feeds on microorganisms that gather around the collar at the base of its flagellum, and they share their energy with other kinds of cells that hold them together and form pores to the outside. However, the basic choice required by their animal nature is made by the individual cells. The sponge has no animal behavior guidance system as a whole. It would be just a multicellular plant, except that its cells are animal-like rather than plant-like. (See diagram of anomalous animals.)

The cellular slime mold is a similar kind of animal, except that the parts are amoeboid animal-like cells, rather than collar flagellates. When a spore from the cellular slime mold lands where food is available, it feeds, grows and reproduces repeatedly, spreading out as far as food is available. But when food runs out, they all move back toward the center, climb on top of one another and form a slug-like animal, which may move around as a unit for a while. Eventually, however, it becomes a stalked, fruiting body from which new spores are released to try their luck at finding new feeding areas. The biological behavior guidance system coordinates their behavior, using messenger proteins to determine the cells to have different kinds of behavior. Their bodies become polarized front to back; each secretes messenger molecules from one end and moves toward the same molecules that are secreted by others. However, the choice required by its animal nature, between feeding or not on the objects it encounters, is made by the animal behavior guidance systems of its amoeboid members. (See diagram of anomalous animals.)

Fungi are so anomalous that they are almost always classified as a third kingdom, separate from both plants and animals. But the recognition that the only animal behavior guidance system that some animals have is an animal behavior guidance system located in their parts that evolved at a lower level of biological organization reveals that fungi are animals of an anomalous, but natural kind.

Fungi are basically eukaryotes, because they have a nucleus. But their animal behavior guidance system is at the prokaryotic level. Fungi acquire energy by ingesting energy-rich molecules (usually after secreting special proteins to promote decomposition outside their bodies), and thus, they need only the prokaryote's mechanisms for selecting which kinds of molecules to admit and which kinds to exclude. Many such mechanisms are located in their cell wall.

In fact, this prokaryotic animal behavior guidance system is organized on two higher levels of biological organization. There are fungus-like protists, such as yeast, at the level of the single-celled eukaryote, and there are fungi, like mushrooms, at the multi-cellular level. (Multicellular fungi are actually multi-nucleated organisms, because their many nuclei inhabit an interconnected labyrinth of cell walls containing many prokaryotic animal behavior guidance systems operated jointly. A multi . nucleated structure is possible, because fungi have no mitochondria to keep under control. But the reason that they lack mitochondria is probably that the prokaryotes from which fungi acquired their animal behavior guidance system did not use the oxygen-consuming process to extract energy from energy-rich molecules.)

There are, therefore, three levels of animals with the simplest kind of animal behavior guidance system: bacteria, single-celled fungi, and multicellular fungi (see diagram of anomalous kinds of animals).

Finally, this same way of combining animal behavior guidance systems with levels of biological organization accounts for what might be called “multisomatic animals,” including insect colonies, hydrozoa (colonies of hydra), corals, and the colonies of blind mole-rats in East Africa. In each case, the only animal behavior guidance systems are the nervous systems contained in the multicellular animals of which the multisomatic organism is composed. Thus, the organism's behavior as a whole depends mainly on the biological behavior guidance system at the multicellular level, and it reproduces as a whole. (See diagram of anomalous animals.)

In insect colonies, for example, the mating flight of the queen sets up a whole new colony composed of her offspring. But sexual reproduction involves the construction of a entire new colony from a fertilized egg cell (at the eukaryotic level). Thus, it must construct organisms at two levels of part-whole complexity. After constructing the queen’s body, her body is used to construct the other members, and the queen becomes the center of a multisomatic structure in which pheromones are used to coordinate the behavior of her multicellular offspring (the same mechanism used to coordinate cells at the multicellular level).

The limitations of such a mechanism are worth noting. It must make sure that pheromones are received by the right animal parts, but since its multicellular parts do nor remain attached to one another like cells in a multicellular organism, the biological behavior guidance system must require the multicellular animals to have certain unchanging spatial relations, or else it could not use the locations of the pheromones to give them different kinds of behavior. Thus, multisomatic organisms have hives, labyrinths of tunnels, or the like in which pheromones can be distributed, and though its parts have locomotion, the whole multisomatic organism is basically sedentary.

All the kinds of animals, including these anomalous heterotrophs, fall naturally into one or another of the categories generated by combining the concept of an animal behavior guidance system with the concept of levels of biological organization. Animals that lack the new kind of animal behavior guidance system that evolves at their own level of biological organization are made of lower level organisms each with the animal behavior guidance system that evolved at a lower level of biological organization.

The classification of insect colonies as an anomalous kind of animal at the social level does suggest, however, that a new kind of animal behavior guidance system may be possible at the social level of biological organization. That is the possibility realized that is realized in a unique way by the evolution of language among manipulative animals, that is, as spiritual animals.

Neurological Stages of Evolution. We have used the series of levels of biological organization to trace the course of evolution up to the stage of multicellular animals, and, together with the explanation of the animal’s need for an additional behavior guidance system, we have catalogued all the basic kinds of animals that come to exist in the course of evolution, including the seemingly anomalous animals. At this stage of biological evolution, we take up the evolutionary stages that depend on levels of neurological organization, and as we have seen. Those stages fall into two distinct series, the animal stages of evolution and the spiritual (animal) stages of evolution, depending on whether they also involve the evolution of an animal on the next higher biological level as well. The animal stages of evolution will be discussed here, and the new wrinkle involved spiritual stages of evolution will not be discussed further until we take up the eighth stage, primitive spiritual animals.

The ontological cause of the animal stages of evolution is, as we have noted, less basic than the ontological cause of the stages of biological evolution, because the causes are levels of part-whole complexity that occur within the animal behavior guidance system at the multicellular level, that is, in the nervous system.

Each new stage is caused by a higher level of part-whole complexity in the organization of neurons, and though that means that what evolves is a basically different kind of animal behavior guidance system, new animal behavior guidance systems are quite different from new biological behavior guidance systems, because they do not have to coordinate the behavior of the lower level material structures of which they are composed. What enables the biological behavior guidance system to guide the behavior of a higher level organism as a whole is coordinating the behavior of the lower level organisms of which it is part. (And as we have seen, they always use the reproductive behavior of their parts in order to generate some of its non-reproductive behavior). These animal behavior guidance systems are composed of lower level organisms, namely, neurons, which are organisms at the eukaryotic level. But their behavior (including their capacity to reproduce) has already been coordinated by the multicellular biological behavior guidance system in constructing the nervous system during embryological development. (And higher level structures of neurons are not even able to reproduce as a whole, that is, apart from the multicellular animals which they are part.)

Instead of coordinating the behavior of neurons, animal behavior guidance systems use the structure that neurons have been given in embryological development, for it is the structure of the nervous system that enables them to guide the behavior of the animal in acting on other objects in space and moving around in space. Neurons can be used to guide behavior, because they have another kind of behavior, called “firing,” by which they can affect one another. Neurons are structural causes of an action potential that propagates along their long axons and that can, upon arriving at a synapse, cause other neurons to fire or muscle cells to contract. (That is, the connection between the stimulation that makes the neuron fire and the neuron’s effects on other cells is an irreversible structural global regularity, or a disposition. and the neuron’s structure is the ontological cause that explains the connection between the efficient cause and its effect.) But what neurons do to other cells when they fire depends on how they are laid out in the structure of the multicellular body, that is, which other cells they affect, and that structure is a contribution of the biological behavior guidance system.

It is levels of part-whole complexity in the structure of the nervous system that cause the series of stages in the evolution of multicellular animals. It is a minor series by comparison with the stages of biological evolution, for it contained within one of the biological stages. But these animal stages are no less essential to the overall course of evolution in the direction of the natural perfection of life. And as in the case of stages of biological evolution, in order to show that animal stages are inevitable, it is necessary to show that each higher level is both possible and functional.

Animal systems of representation. The challenge of showing the inevitability of animal stages of evolution is just opposite to the challenge in the case of biological stages. It is the function, rather than the possibility of such levels that is problematic.

The possibility of another level of biological organization was the main challenge in showing the inevitability of another stage of biological evolution. But the possibility of higher levels of neurological organization is not very problematic (though there is still something to be shown). The nervous system is constructed by the multicellular biological behavior guidance system, and since that is the mechanism of embryological development, even very complex nervous systems do not seem to be beyond its reach. (And as we shall see, the inevitable limits to the complexity of multicellular structures that can be constructed by it are overcome by a form of reproductive causation that is contained in the nervous system as parts of the process of neurological development.)

On the other hand, whereas the function of higher levels of biological organization was obvious in the size and scale of the behavior they afford, the function of levels of higher levels of neurological organization is not obvious. Indeed, most levels of neurological organization are not even currently recognized in neurophysiology. We begin, therefore, with the basic function of higher levels of neurological organization.

The basic function of all higher levels of neurological organization is to serve as an animal system of representation. This function derives from the nature of animal behavior, and thus, it is part of the animal behavior guidance system. And more complete ways of serving this function depend on higher levels of neurological organization.

Animals need an animal behavior guidance system, because in order to acquire the free energy needed to fuel their reproductive cycles, they must act on other object in space. They cannot sit back and absorb photons like plants. But in order to guide behavior to act on other objects in space, the animal behavior guidance system needs to take into account not only the kind of object, but also its location. Though the kind of object is relevant in selecting the kind of behavior to generate, its location is relevant in generating behavior that is directed at the object, whatever goal is chosen. And this spatial aspect of its behavior is, as we have seen, a source of potentially great animal power.

Increased animal power can come from making the spatial aspects of their behavior depend on the spatial aspects of the situation with which it will engage. By imposing a geometrical structure on a wide region of space, such animals can use the free energy there to do work — much like a giant machine in the region, except by the more efficient means of moving an animal body around in space and acting on particular objects locally.

In the first instance, therefore, what the animal needs to be more powerful is some way of determining how to move around in space relative to objects in order to put its body in a position to act in the appropriate way, whatever its goal. Even more power to cause changes in a large region that would otherwise not occur would come from being able to anticipate the effects of motion on locations. Still more power would come from the ability to anticipate the effects of the geometrical structures of objects on how they interact. Though such spatially adapted animal behavior would require more free energy than sedentary life, the additional relevant conditions it could control more than covers the cost.

The mechanism that actualizes this possible power must be part of the system that is responsible for guiding animal behavior, that is, part of the animal behavior guidance system.

Like any behavior guidance system, as we have seen, the animal behavior guidance system must serve three subfunctions in order to select between incompatible kinds of behavior. It must register input, select the appropriate kind of behavior, and generate output. In multicellular animals, these subfunctions are served by systems made of neurons, and they will be called, respectively, the sensory input system, goal selection system, and behavioral output system.

Sensory input already has the function of representing the object in the animal behavior guidance system. But in order for animal behavior to be adapted to the spatial aspects of the situation, the sensory input system must work together with the behavioral output system, as a system for representing all the possible ways adapting animal behavior spatially.

Sensory input must enable the animal behavior guidance system to select the appropriate kind of behavior toward the objects that the animal encounters. The object may be food, a predator, a mate, or whatever, and the animal behavior guidance system must generate behavior that is appropriate to it, such as, ingesting the object, escaping it, mating with it, or whatever. (Though animal behavior includes mating, it is all non-reproductive work as far as the biological behavior guidance system is concerned, because animal behavior, as such, is just a special kind of behavior generated during the growth phase of the reproductive cycle. Mating is just another way of preparing the conditions for the biological behavior of sexual reproduction.)

But whatever the goal of animal behavior, animal behavior is more powerful when it is adapted to spatial aspects of the situation, and that is another function of sensory input. But to serve this function, the sensory input system must work together with the behavioral output system, that is, as an animal system of representation.

“Animal” system of representation is an appropriate name for this mechanism, since its function is to represent the objects on which animals must act so that their behavior can be guided spatially in relation to it. Since the object is represented by a system that is based on an interaction between the sensory input and behavioral output subsystems of the animal behavior guidance system, the animal system of representation is more than just a picture of the object. It gives the animal a conception of the object. The object is what its behavior is directed at, but if we set aside the specific goals it may have in regard to the object, it is represented in such a way that behavior can be guided in relation to it. And the conception is more complete, the more behavior is adapted to spatial aspects of the object, which depends on the animal’s level of neurological organization.

The simplest animal system of representation occurs in the “telesensory animal,” that is, animals that can perceive objects at a distance from their bodies. But the telesensory animal’s conception of the object is not a conception of the object as located in space, even though the object is typically located at a distance from the animal’s body and it guides locomotion in relation to the object. Though the object itself must be represented explicitly in order to determine its kind, its location is represented only implicitly in the instinctive routines by which the animal representation guides locomotion in relation to it.

The ability to think of the object as being located in space requires a conception of space. That is provided, as we shall see, by a faculty spatial imagination which enables the animal to think about the effects of locomotion (and motion generally) on the relations among objects in space. That occurs in subjective animals, and it is what I will call a conception of the object as located in space, because it enables them to see the object against the background of what is possible as a result of objects moving in space. (That is, spatial imagination uses sequences of images over time to represent the consequences of locomotion (and turning), and such sequences are the background in which objects are represented.) However, though the object may have a geometrical structure, the subjective animal does not have a conception of the object as having a geometrical structure. It has only the conception of the object as located in three dimensional space.

The ability to think about the object as having a geometrical structure requires a conception of geometrical structure. That is provided, as we shall see, by a faculty of structural imagination which enables the animal to think about the effects of manipulating the object on how it appears, how its structure changes, and how it relates to the geometrical structures of other objects in space. The actual geometrical structure is seen against the background of what is possible by manipulation (once again, by using sequences of images over time to represent the kinds of events that manipulation would cause). This new faculty occurs in what will be called manipulative animals, and since they already have a faculty of spatial imagination, it gives them a conception of the object in space as having a geometrical structure, for it can see the object against the background of what its geometrical structure makes possible.

Animal stages of evolution. Each way of these representations of the object serves the function of an animal system of representation more completely, but each depends on a higher level of neurological organization. These levels are the ontological cause of the animal stages of evolution, and each requires certain additional subsystems to serve their increasingly demanding functions. I will use their functions to introduce the animal stages of evolution. And the nature of somatosensory animals will be explained by contrast to all of them.

Somatosensory animals. Before considering what is required to serve the function of the animal system of representation, it should be emphasized that it is possible for animals not to have an animal system of representation. That is, even the object (not just its location) may be represented only implicitly in the animal behavior guidance system. In somatosensory animals, with the simplest animal behavior guidance systems, sensory input is still caused by the object, and, as always, sensory input is used to select the goal of animal behavior. But sensory input does not represent its cause as an object. At most, it might be said to represent the goal of the behavior it triggers, since it can select the kind of behavior. What serves the function of the system for representing the object is, in effect, the structure of the animal’s body.

In the somatosensory animal, it is contact with the object that guides animal behavior. In its decentralized nervous system, the object can be represented by a single somatosensory neuron, because its behavior is selected and generated by local connections between somatosensory input and motor neurons controlling nearby parts of the body. When contact reveals that the object is of the appropriate kind, behavior acts on the object at the location from which the input about its kind comes. It is a local reflex, though it may recruit appropriate behavior in other parts of the body. And reciprocally, similar reflexes in other parts of the body may trigger its motor neurons. But no centralized mechanism for guiding the behavior of the whole animal is needed. It is just what results from an equilibrium among many localized systems for guiding animal behavior.

Somatosensory animals include hydra, jellyfish, sea stars and brainless chordates (like Amphioxus). When an edible object brushes up against one of the hydra's tentacles, for example, it responds by stinging them and contracting. That reflex recruits other tentacles to contract as well, and thus, together, they pull the object contacted into its gastrovascular cavity. Sea stars also have locomotion, but it is guided locally, as each arm recruits the other arms (and its many little feet) to move in a certain direction because of the kinds of objects it contacts.

With only an implicit representation of the object, the somatosensory animal does not have a conception of the object. Though it responds according to the kind of object, no nervous mechanisms register input about its location in order to guide behavior in relation to it, because the object is always located where the sensory input is received and behavioral output is generated. Even less do somatosensory animals have a conception of the object as located in space, for it is the object’s location in space that causes it to be represented as an object at all.

Since the object need only be at a certain location to be represented as an object at all, it is the biological behavior guidance system that gives the animal its merely implicit representation of the object. Not surprisingly, therefore, this is also how behavior is “guided” to act on objects in animals at lower levels of biological organization, such as animal-like protists and bacteria. In paramecia, for example, the system for selecting whether to ingest objects or not is located in the oral groove where the object comes into contact with the animal. And the amoeba engulfs food particles wherever on its body they are encountered.

The most basic way that an animal system of representation makes animals more powerful than somatosensory animals is the ability to guide locomotion in relation to distant objects.

Though somatosensory animals may have locomotion, it is not guided in relation to distant objects in space, and thus, the geometrical structure they impose on the thermo­dynamic flow in the region is still short-range, channeling only the free energy of objects they happen to contact to fuel their reproductive cycles and avoiding only local hazards.

But when locomotion is guided in relation to distant object, what imposes a geometrical structure on the thermo­dynamics flow in the region is animal behavior itself, rather than merely the structure of the animal body. But guiding locomotion requires having a representation of the object that indicates its location relative to the body even when it is at some distance from the animals.

Sensory input from the distant object is obviously required for an animal representation of it. But in order to be useful in guiding locomotion, sensory input must be able to reveal its kind as well as its location. Unless the animal can also tell what kind of behavior to generate in relation to the object, guiding locomotion in relation to it will not control relevant conditions. In what follows, I will assume that the animal representation also indicates the kinds of distant objects as, not only their locations.

Telesensory animals. Telesensory animals are the simplest animals with an animal system of representation. The most obvious indication of their higher level of neurological organization is that their nervous system is centralized, whereas somatosensory animals have decentralized nervous systems. Centralization is required in order to guide behavior in relation to objects located at a distance from their bodies, because only groups of motor neurons can generate whole body behavior, such as swimming in fish or walking in land animals, and the same sensory input must control all of them. Sensory input also requires a higher level of neurological organization, because only groups of sensory neurons, as in the retina of the eye, can register effects of distant objects in a way that reveals information about their kinds and locations.

Sensory input from distant objects does not, by itself, contain enough information to guide locomotion in relation to it. In order to determine the object’s location, there must be an interaction between mechanisms serving the subfunctions of sensory input and behavioral output in the animal behavior guidance system. (Their interaction is also where we will find the higher level of neurological organization that gives animals spatial imagination, and the yet higher level that gives animals structural imagination.)

Sensory input from an object located at a distance from the animal, or “telesensory input,” can guide locomotion only when it is combined with input about the current condition of the animal’s body. For example, to use visual input to determine what is located in different directions, animals with eyes must take account of which way their heads or eyes are pointing when visual input is received, and that requires input about how the current condition of their eyes, head and body. I will call it input about the “bodily condition.” Thus, the animal representation of the object is telesensory input registered in a way that indicates the bodily condition. That is the animal’s “perception” of the object.

Since the animal must behave in various ways to gather information about what is located in each direction, perception generally involves a new kind of behavior. This holds of hearing and olfaction as well as vision. I will call it “inquisitive behavior,” in order to distinguish it from behavior directed at more basic goals, such as acquiring food, protection, mating and the like. Inquisitive behavior transforms telesensory input into feedback from its own motor output, making perception an active process. But whenever telesensory input from the object is registered in the nervous system according to the bodily condition at the time, it contains information that can be used to guide locomotion in attaining its goals with the object. This combination is an animal representation, because the animal can extract information from it about which way to move its body in order to change its spatial relation to the object appropriately. It is a perception of the object that implicitly contains information about its location.

Animal representations of objects also make it possible for telesensory input from an object at one time (when the object has one location relative to the animal), to be used in guiding the animal's behavior at another time (when the object has a different location relative to the animal). And in some telesensory animals, such as bees, so much information about the locations of objects in the surrounding space is recorded that their animal representations are implicitly maps of the relations of salient objects in their territories.

The basic structure of the animal system of representation can be seen by comparing the telesensory animal behavior guidance systems with that of the somatosensory animal. (See the accompanying diagrams of their animal behavior guidance systems.)

The animal behavior guidance system of somatosensory animals (and animals at lower biological levels) are so simple that their three subfunctions work together in the same way as the biological behavior guidance system (though they may be located throughout the animal body and recruit similar behavior in neighboring systems). Without an animal system of representation, they are unable to perceive objects at all.

In the telesensory animal behavior guidance system, what constitutes the animal system of representation is an interaction between mechanisms serving the sensory input and behavioral output subfunctions which is independent of the mechanisms serving the selection subfunction. An animal representation is constructed by combining telesensory input with input about the bodily condition. The bodily condition, such as which way the head and eyes are pointing, affects how telesensory input is registered, and how that input is registered is then used to determine how the animal moves, say, if it selects a goal that requires approaching the object. In telesensory animals, this mechanism is “hard wired” into the nervous system by the biological behavior guidance system in constructing it, and it is just a more or less elaborate set of rigid, instinctive routines that have been naturally selected for the power they afford.

The centralization of the nervous system is so obvious that no one denies the difference between "somatosensory" and "telesensory" nervous systems (though they many not use these terms). But the difference between them is not usually explained as a difference in level of neurological organization, and the main reason is that it is not recognized that there is a third level of neurological organization, much less a fourth. However, given that the function of the telesensory level of neurological organization is to provide an animal system of representation, however, we can see how higher levels of neurological organization could make animals even more powerful, including both spatio-temporal and structural imagination, because it is evident in the structure of their required subsystems. The following functional diagrams suggest their levels of part-whole complexity. These diagrams are explained more fully in relevant chapters, but even a gross impression of how they work shows how theses two higher levels of neurological organization would cause two step-like increases in animal power beyond telesensory animals..

Subjective animals. In subjective animals, the telesensory animal’s hard wired animal representation of the object is replaced by a kind of perception that is backed up by a faculty of imagination. The sensory input system still enables the animal to perceive the object in a way that guides locomotion in relation to it, but such perceptions are generated as part of a new interaction between the telesensory input and behavioral output systems, one in which covert locomotion in some direction can call up sequences of “local images” from memory representing the local scenes that would be encountered in moving in that direction (given a certain starting point).

What makes such spatial imagination possible is, as this diagram suggests, a higher level of neurological organization in both the sensory input and behavioral output subsystems. (The higher level is indicated by the two circles within the enlarged square, representing the necessary subsystems.) Telesensory images are recorded in memory in sequences according to the locomotion that connects them (with memory using its own input from the current bodily condition), so that they can be called up in sequences from memory. (Since they are sequences of images over time, they are labeled “spatio-temporal images.”)

Once spatial imagination has been set up in the brain, therefore, to perceive an object is to be able to imagine how its spatial relations to objects would change, if the animal were to move its body in relation to it. And to imagine what would happen if the object were to move relative to its body and other objects. That is the effect of covert locomotion on subjective memory. To see the local image (and the objects it includes) as located within the map of its territory is to perceive the object as located in space. It also means perceiving its body as located in space, as we shall see. The subjective animal has, therefore, a conception of an object as located in space.

Manipulative animals. In the manipulative animal behavior guidance system, the sensory input system is still the animal’s perception of the object as located in (and potentially moving in) mammalian space. But more is perceived, because sensory input also represents the object as having a geometrical structure. Within the subjective animal representation of the object as located in space (the object in the local image which is part of its map of the territory), there is a further interaction between the sensory input and behavioral output systems in which covert manipulation can call up sequences of telesensory (and tactile) images of objects as they would appear if they were manipulated in certain ways. That yields an object image in the local image.

What makes structural imagination possible is, as the diagram suggests, a yet higher level of neurological organization in both the sensory input and behavior output subsystems (as indicated by the circles within the circles within the enlarged squares). (The connections representing perception and input from the current bodily condition, which are the underlying structure of the animal system of representation connecting the sensory input and behavioral output systems) are suppressed in this diagram for simplicity.) In manipulative animals, telesensory images of objects are recorded in memory in sequences along with tactile images from the hands according to how the object is being manipulated at the time (with memory using its own input from the current bodily condition), and these images can be called up in sequences from memory. (Since they are sequences of images over time, they are labeled “structuro-temporal images.”)

Once structural imagination has been set up in the brain, therefore, to perceive an object in space is not only to be able to imagine what would happen if it (or its own body) were to move around in space, but also what would happen if its hands were to manipulate the object in some way (for example, how it would appear if turned upside down or backside forward). That is to perceive the object in space as having a geometrical structure. Manipulative animals have, therefore, a conception of the object in space as having a geometrical structure.

The functions of sensory input and behavioral output systems, of the new subsystems, and then yet newer sub-subsystems that come to exist within them suggest the way in which higher levels of neurological organization can be functional in the sense of opening up, step by step, entire, new ranges of possible powers that animal behavior might evolve.

Starting with the telesensory stage, one new stage actualizes the potential power of spatial imagination, and after that, another new stage actualizes the potential power of structural imagination. Animal power is increased in each case by making the spatial aspects of animal behavior depend on spatial aspect of the world. The spatial aspects of the world they are exploiting are ontologically basic. In one case it is an intuitive understanding of spatial causation, and in the other it is an intuitive understanding of structural causation. These faculties of imagination approach a natural perfection for neurological mechanisms of their kind as part of the natural perfection of the multicellular animals to whose power they contribute, but since such powers are useful only in some ecological niches, they become most powerful only in some species of multicellular animals.

In each of the following three sections (telesensory animals, subjective animals, and manipulative animals), the function, evolution and structure of the nervous systems at each of their three levels of part-whole complexity are discussed in detail. Since higher levels of neurological organization can evolve only after gradual evolution has made mechanisms on the lower level of neurological organization reliable, if not perfect, in serving their functions, each level of neurological organization entails a stage of animal evolution in time, just as each level of biological organization entailed a stage of biological evolution. These are the animal stages of evolution.

Somatosensory animals do not represent a distinct stage of animal evolution, because they do not evolve after the evolution of multicellular animals, but as part of it. Simply having a nervous system does not put somatosensory animals on a higher level of organization than other multicellular organisms, because it is just a variety of multicellular organism that fills a kind of ecological niche, namely, acquiring free energy ingesting energy-rich objects. The structure of the somatosensory nervous system is basically just the structure of the body constructed by the mechanism of embryological development, because all three subsystems of the animal behavior guidance system are served locally by three different kinds of neurons at each location in the body: sensory neurons (sensory input), interneurons (goal selection), and motor neurons (behavioral output).

A higher level of neurological organization is required, as we have seen, for the animal to have an animal system of representation at all, and even in telesensory animals, single neurons can no longer serve the basic functions of registering telesensory input and generating behavioral output. Each such subfunction requires a whole group of neurons working together. That puts telesensory animals on a higher level of neurological organization than somatosensory animals, and as the diagrams suggest, higher levels of neurological organization involve higher levels of part-whole complexity within the mechanism serving the same basic subfunctions, sensory input and behavioral output. As we shall see more clearly when we consider the structure of the brain, the basic functions of generating perceptions and using them to guide behavior depend on two yet higher levels of neurological organization: circuits of groups neurons in subjective animals, and interactions among several similar circuits of neurons in manipulative animals.

Most animals, from worms and insects to reptiles and birds, are at the telesensory level of neurological organization. But the animal stages of evolution are somewhat more complicated than the stages of biological evolution, because there are two forms of embryological development and, thus, two series of levels/stages in multicellular animals. And the difference is relevant, because their biological behavior guidance systems use basically different mechanisms to organize groups of neurons to act as a whole within the nervous system. One uses ganglia, and the other uses two dimensional arrays of neurons laid out in a special neural tube. As a result there are two basically different kinds of telesensory animals, and only one of them is able to evolve beyond the telesensory stage. Invertebrates never evolve a subjective behavior guidance system, and we must explain why.

The gradual evolution of embryological development. The evolution of the mechanism of embryological development is responsible for the most spectacular punctuation in the whole course of evolution, the Cambrian revolution at the very beginning of the fossil record some 600 million years ago, when many different species of multicellular animals suddenly showed up. Only when animals evolved hard parts, like shells, did fossils form, and the same mechanism that constructs such hard parts also constructs the nervous system.

Tracing the actual evolution of the mechanism of embryological development on earth should settle any doubts that may remain about the inevitability of the evolution of multicellular animals, because it shows concretely how such a mechanism lies within the range of variations on animal-like protists.

This rather technical history, however, serves an additional function in this ontological argument, because it leads to an explanation of the difference between proterostomes and deuterostomes (that is, between most invertebrate development and development in chordates, such as vertebrates and mammals). That will account for the radical difference between two groups of telesensory animals (invertebrates and vertebrates), and the nature of the difference between them will explain why proterostomes do not evolve to the third and fourth animal stages of evolution.

The origin of the mechanism of embryological development. Clues about the evolution of animals can be found by comparing how the various kinds of animals develop. The first steps in embryological development are least likely to have changed during evolution, for whatever the mechanism, variations in it would probably throw the whole process off track. Evolution occurs mostly by adding new structures to the process. And we can see how animals with nervous system began by identifying the first form of development. Let us compare the three basic forms of development.

Gastrulation. More complex animals, both proterostomes and deuterostomes, develop by a process of gastrulation. The fertilized egg cell is an unusually large cell, and asexual division produces many daughter cells (cleavage). They secrete a fluid in their midst and arrange themselves in a layer, enclosing it like the surface of a sphere. They are the blastula, and the cell-free area in their midst is the blastocoel.

Gastrulation follows the formation of the blastula. Its function is to establish a second layer of cells beneath the first. The cells destined to become the second layer, or endoderm, are one hemisphere of the blastula. With more energy-rich yolk from the cytoplasm of the egg, they are larger than the cells in the other hemisphere, which becomes the ectoderm. The second layer forms by a folding inward (invagination) that never breaks the surface of the sphere: At about the margin between the two hemispheres, cells on the surface of the blastula bend inward and start moving into the blastocoel, aligning themselves along the underside of the sphere's surface. Ultimately, about half the surface of the original sphere turns itself inside out to form the second layer of cells on the underside of the other half of the original sphere. But the resulting two-layered surface is not a hemisphere: The missing hemisphere shrinks to the size of a hole in the surface of a new, yet incomplete sphere. The hole, through which the endoderm has disappeared, is the blastopore, and the inner chamber, now lined with endoderm, is the archenteron. Finally, a second opening is made through the two layers of cells, forming a digestive tract between it and the blastopore. Differences that begin at the this point distinguish proterostomes from deuterostomes.ⁱⁱ (See diagram of Development in gastrulating animal.)

Planuloid development. Animals with nervous system could not have begun with gastrulation. The process involves such a complex coordination of the behaviors of so many different cells that it could not possibly have been the first step by which protists organized themselves multicellularly. Development occurs in another way in two classes of animals, flatworms and coelentrates. The two layers of cells are produced by a process, which I will call planuloid development.

A blastula still forms after the cleavage of the egg, but the second layer of cells is formed by the inward migration of cells, usually from all parts of the surface of the sphere. They clump together at the center of the sphere, separating themselves from the outer layer of the blastula, and then the outer surface of the inner clump makes contact with the outer sphere, or ectoderm. This is the planula. (See diagram of Planuloid development) The endoderm is formed by a split that starts at the center of the solid clump of cells and continues outward in one direction toward the ectoderm, where an opening is made for the mouth. The result is a gastrovascular cavity, rather than a digestive tract, for there is no second opening. The one opening is both mouth and anus. The cavity not only digests food but also circulates it to all parts of the body.

In coelentrates, such as the hydra, the gastrovascular sac develops long, hollow tentacles around the mouth which are used to paralyze prey and pull them into the mouth. But flatworms have a bilateral symmetry. The mouth opens from the middle of the body toward the ground, and instead of a radial symmetry around it, one of the directions becomes the longitudinal axis of the body, and the perpendicular direction has a bilateral symmetry.

Ectolecithal development. Coelentrates and flatworms, as we mentioned, are the simplest kinds of animals. But even their planuloid development is too complex to have been a variation on protists. After the solid core of cells has formed inside the blastula, and before the inner split has opened as a gastrovascular cavity, cilia grow from the ectoderm and the planula swims around for a while. But this early, pre-sexual stage of its life is surely not the first form that animals took, because it has no way of acquiring energy. It is still living from the energy reserves of the egg. The clue to the origin of multicellular animals can be found in a third kind of development which occurs only in certain kinds of flatworms.

The eggs of these flatworms develop in a medium of energy-rich yolk supplied from the outside by nurse cells (ectolecithal development). From the cells produced by the cleavage of the egg cell, first, the mouth (pharynx) forms. Attached to these cells, another group of cells forms a sac to receive what the mouth swallows; they are the primitive endoderm, or gut. The ectoderm is formed by a third group of cells that constructs an outer layer of cells in the yolk by stretching themselves out from the mouth through the yolk around the gut. The embryonic mouth then swallows the remaining yolk, which fills the gut, or gastrovascular cavity.ⁱⁱⁱ (See diagram of Ectolecithal development.)

Ectolecithal development is unique. It occurs in just a few species of flatworms, but in no other animals. It would be difficult to explain why there is such an unusual kind of development unless it is the earliest condition. And it suggests how animals may have evolved.

The origin of ectolecithal development. The process of ectolecithal development requires only three kinds of cells, each with a distinctive kind of behavior. They can all behave at the same time, since no movement relative to one another in involved. Thus, this random variation would have required only a few cells (maybe as few as twelve). An amoeba's cycle of sexual reproduction could well have produced that many offspring at once. Assuming that it happened on some mechanism for determining its offspring to three different kinds of behavior, this lineage could have begun, if each kind of cell remained attached to one another and to at least one of the other kinds of cell in an asymmetrical way. By synchronizing the amoeboid contractions of the mouth cells, the group could trap and surround animal-like protists for digestion. The energy supplied by their ingested bodies would select a reproductive cycle of this kind, if it were possible at all.

A new source of energy is probably the only way that such an unlikely process could have been selected. It was probably not to consume plants, since a multicellular body is no better suited than single-celled animals. Nor is a multicellular body needed to ingest prokaryotes. They are on a lower level of biological organization and animal-like protists already feed on them. Thus, multicellular animals were probably selected in the first place as carnivores, which preyed upon larger animal-like protists that, before them, were at the top of the food chain. Once the means of constructing multicellular bodies had evolved, some variations would, of course, eventually evolve ways of using it to acquire energy by ingesting plants and prokaryotes.

This origin of animals would account for the ectolecithal development in primitive flatworms. It now occurs in eggs, where nurse cells supply the yolk, but at first, the offspring may have been constructed in the gut using the energy-rich molecules available there, making the gastrovascular cavity do double service as a womb. The biological behavior guidance system could select the behavior required for gestation as an extra stage in the behavior of reproduction by turning off the behavior involved in digestion. Amoeboid cells already have the capacity to contract and relax depending on the kind of object they encounter, and thus, the same cells could play the roles of both muscles and neurons in guiding the organism's behavior as a whole. Swallowing, for example, could be a contraction generated by a signal exchanged among the mouth cells when any member made contact with an animal-like protist. It could even have been an electromagnetic signal, like neurons, since cells of many kinds are responsive to them. Neurons would differentiate as variations of ectodermal cells that signalled cells to refrain from feeding in hazardous situations, for that would enable them to complete their reproductive cycles while others did not. That would explain why neurons always differentiate from the ectoderm, never from cells of any other kind.

Three basic kinds of cells. This explanation of the origin of animals with nervous systems depends on the capacity of offspring of a fertilized cell to differentiate into three different kinds of cells. The mechanism of differentiation lies in how the egg cell is prepared. By leaving different messenger proteins in different parts of the cortex or cytoplasm of the egg cell, cleavage gives different daughter cells different messenger proteins. The nucleus must enable the chromosomes to affect different parts of the cytoplasm in different ways, or else it could not set up the process involved in reproduction. Thus, the preparation of the egg cell would merely elaborate an existing mechanism. The messenger proteins would be keys for opening up certain special chromosomes, in addition to those used for ordinary housekeeping activities, thereby generating special kinds of behavior in them. And assuming the chromosomes are also opened up differently at subsequent stages of development, the differences would be permanent.

This way of determining the most basic differences among cells, which are responsible for the whole process of development, would be an elaboration of the protein mechanisms for handling the chromosomes, sorting them out, and forming a nucleus that were introduced with the evolution of eukaryotes. The mechanism by which sex is determined makes it clear that the nucleus handles different chromosomes in different ways.^iv Since this mechanism is so basic to the operation of the eukaryotic cell, evolutionary change would build on it by adding new steps or new kinds of behaviors to each of the basic cell kinds at each step. Nor could it change easily in the course of evolution.

Only three kinds of cells are needed to account for the process of development. They would differ from one another in how cells of the same kind remain attached to one another and how they relate to the other two kinds of cells. Cells that form the ectoderm must attach to one another on four sides as the 2-D surface of a sphere while orienting themselves to the mouth cells located among them. The inner gut cells must also attach to the mouth cells, but they would form themselves into a 3-D ball whose outer surface eventually attaches to the ectoderm. In addition to attaching to the other two kinds, the mouth cells would form an opening in the blastula. Behavior like this would require each cell to generate different kinds of behavior towards other cells on each side, but that is within the range of what eukaryotic cells can do, as the preparation of the egg cell and the asymmetrical structures of animal-like protists demonstrate.

A second kind of behavior is also required. Once they are attached to one another, the interactions of the different kinds of cells must set up the gradients of messenger molecules in which cells at different locations can be determined to different kinds of behavior, as in multicellular plants. It is not known how these gradients work, but we can think about what they must be doing by supposing that a gradient involves a pair of messenger proteins with one kind being concentrated at one extreme along its direction and the other being concentrated at the opposite extreme in that direction; their relative strength for any cell would indicate its location. One gradient would extend between the mouth cells and the other extreme of the blastula (oral and aboral poles). The mouth cells surely have a gradient around the opening that they form, which would give the blastula a gradient perpendicular to the first. And beside orienting themselves in the blastula and picking up its gradients, the inner-gut cells must have a gradient of its own that determines the center at which the split forms for a digestive cavity.

The evolution of other forms of development. The small scale and simple behavior required of such proto-flatworms, together with our explanation of the source of energy for development, makes it plausible that animals with nervous system originated from an amoeba whose offspring after mating included these three different kinds of cells. And it is easy to see how planuloid development and gastrulation could have evolved from it, thereby suggesting the basic evolutionary relationships among animals with nervous systems.

A simple rearrangement of the three kinds of behavior found in the primitive, ectolecithal development accounts for planuloid development: After cleavage, the ectodermal cells go to work, first, constructing the blastula in which the mouth cells have a location because of where the division of the egg cell has left them.^v The gradients in the blastula are oriented around the mouth, and once the inner gut cells have migrated inward, formed a solid core, and made contact with the ectoderm, the split forming in their midst could be made to open up toward the mouth's location on the blastula by the gradients in the ectoderm. Thus, all the steps in planuloid development can be explained as a result of the interactions among the three original kinds of cells.

Gastrulation can likewise be explained as a modification of planuloid development in which one of the original three kinds of cells drops out of the process. Once again, the blastula is the result of the ectoderm-forming cells, and mouth-cells have a special location in it, establishing its gradients. But instead of cells migrating inward to form the inner core of cells, the second layer of cells is formed as a result of the behavior of the mouth-cells. That is, invagination can be explained as a variation on the behavior that makes an opening in the blastula and swallows. It is as if one half of the hemisphere swallowed the other half, turning the other half inside out to form a second layer of cells beneath the cells of the first half. Gastrulation results in a digestive tract with two ends. This could also be explained as a elaboration of the behavior of the mouth cells. After leading the invagination involved in gastrulation, the mouth cells eventually make contact with a special location on the blastula and form an opening by interacting with the ectodermal cells there. The clump-forming cells that supplied the endoderm for the planuloid animal have no role in forming the two layers of cells.

Embryological development is our best clue to the branchings of kinds of animals in evolution, and the implications of this account of the origin of multicellular animals with nervous systems can be made explicit by outlining the evolutionary tree to which it leads. We have found that the flatworms were the first multicellular animals. The original ectolecithal development evolved into the planuloid development of flatworms. And coelentrates and gastrulating animals both evolved from planuloid flatworms.

Gastrulating animals are of two kinds, proterostomes or deuterostomes, depending on the fate of the blastopore, the opening through which the mouth cells invaginate. In proterostomes, the blastopore becomes the mouth and the second opening becomes the anus, whereas in deuterostomes, the blastopore becomes and the anus and the second opening becomes the mouth. This is either an early branching among gastrulating animals or each evolved independently from the planuloid flatworm. And there is a second major difference between them, concerning how they form a mesodermal coelom, which suggests the fate of the third kind of cell found in the most primitive development that seemed to drop out with the evolution of gastrulation.

A mesodermal coelom is a cavity formed within a layer of cells that lies between the ectoderm and endoderm. It is the source of internal organs, including muscles, gonads, the circulatory system, excretory system, and the like. Only the more advanced proterostomes form a coelom at all. (Proboscis worms and round worms have no true coelom, although they do have a digestive tract.)

In proterostomes, it is constructed from a special pair of cells which were determined by how the cleavage of the egg divides up the egg cortex and cytoplasm. As a result of how the blastula is formed and gastrulation takes place, these cells wind up near the blastopore, which has become the mouth.^vi After gastrulation is complete and the anus is formed, one cell on each side of the blastopore migrates into the area between the ectoderm and endoderm, multiplies into a solid mass of cells, and a mesodermal coelom is formed by a split that starts in their midst. The process is called "schitzocoelous." The mesodermal cells are probably descendants of the third kind of cell from the primitive, ectolecithal development, which formed a solid clump of cells in which a split can develop. With their backs facing either the ectoderm or the endoderm, the fronts of these cells face a fluid-filled space formed by their splitting, and a 2-D gradient set up in it probably determines the cells at different locations to become different kinds of organs. The 2-D gradient in the ectoderm and endoderm enable them to locate themselves in the body. (See diagram of Schitzocoelous.)

Deuterostomes take a different tack, and as we shall see, it makes all the difference in their evolutionary destiny. The third kind of cell drops out again as gastrulation evolves from planuloid development. But the deuterostome forms a mesodermal coelom by enterocoelous, a continuation of the behavior of the mouth-cells that accounts for gastrulation. That is, after the endoderm invaginates, but before the mouth-cells make a second opening in the ectoderm (the animal's mouth, in this case), a second invagination takes place, this time from the endoderm into the blastocoel, the volume inside the original blastula that is now located between the endoderm and ectoderm.^vii No cavity is formed by splitting in a solid core; deuterostomes make no use of the innerªgut cells from the primitive flatworm development. (See diagram of Enterocoelous.)

If this is indeed how animals with nervous systems evolved, then the primitive flatworm is their progenitor and all their kinds can be classified according to their modifications of its kind of embryological development. There are three branches. The simplest coelentrates have a larval stage that involves the planula. The other coelentrates and ctenophora have evolved from them, although some more advanced kinds have evolved a form of gastrulation on their own. Thus, these radial animals are one branch. On the second branch are proterostomes, and on the third are deuterostomes. Differences in how coeloms are formed accompany this defining contrast. As we shall see, this difference in embryological development explains the surprisingly radical differences between telesensory proterostomes and deuterostomes.

The proterostome nervous system development. Neurons always develop from the ectoderm. From the beginning, on our speculation, the chromosomes containing the genes that transform basic cells into neurons are opened up by the protein keys in the ectoderm-forming cells. But some additional factor must turn those genes on, since not all the cells of the ectoderm become neurons. The mechanism is not fully understood, but it apparently depends on gradients in the ectoderm. The cells becoming neurons can be evenly distributed over a region^viii or determined by singularities in the gradient. In the proterostome, gradients in the ectoderm (or the effect of special mesodermal cells on them) are responsible for cells becoming neurons.

More complex interconnections among neurons in proterostomes are made in structures, called "ganglia," which are located in various places in their bodies and connected by bundles of axons. In each ganglion, cell bodies are arranged on the outer surface, and its core is a neuropil where the processes synapse with one another. Axons of proterostome neurons branch near the cell body. One branch leads into the neuropil, and the other branch joins a nerve connecting to other ganglia or innervating muscles or sensory receptors at the periphery. Ganglia can develop when one or more cells that are determined to become neurons at some location multiply and form a cluster. When the cluster establishes its own gradient, their locations in it can determine neurons to become specific kinds as well as enable them to make quite precise connections with one another in each ganglion or between them.

The ganglia form in the ectoderm, and they must be interconnected to works as an animal behavior guidance system. The gradients of the ectoderm are used to connect neurons with one another as well as with sensory receptors on the input side and muscle cells on the output side. When cells become neurons, they develop processes, dendrites and axons, which extend out from the cell body and eventually form synapses with certain cells that they encounter. The axons are guided to other ganglia, muscles or sensory receptors as they form by following the ectodermal (or endodermal) gradients. Neurons at different locations in the body are thereby interconnected by nerves.

The typical structure of the proterostome nervous system is a set of ganglia in the ectoderm that are connected with one another and the ultimate inputs and outputs throughout the body. That is, the nervous system is laid out in the outer skin of the multicellular animal. The animal's behavior as a whole depends on the equilibrium reached by its entire nervous system, but that equilibrium depends, in turn, on the equilibria reached in each of the ganglia as they interact with one another by way of the nerves connecting them, given the sensory input from the rest of the body. We can see how the basic structure of the proterostome nervous system follows the gradients of the ectoderm by looking at the nervous systems of simpler animals, those with a planuloid development, because the gradients in the proterostome are simply how gastrulation has modified them.

The bodies and nervous systems of flatworms and coelentrates form from a larval stage called the planula, which as we have seen, is produced by the interaction of the three basic kinds of cells. The ectodermal gradients depend on the location of the mouth cells, and when the inner core of cells joins the ectoderm, it picks up the ectodermal gradients, enabling the split that forms in their midst to open up in the direction of the mouth. The mouth is the only opening, and body is a sac formed of two-layers of cells. There is a gradient between its oral and aboral poles and another gradient running around the body perpendicular to it. (See diagram of The planula.)

The body of the hydra, for example, is complete, once tentacles form around the mouth as elongated extensions of this gastrovascular cavity. Its nervous system is just a network of neurons differentiated at random in the gradients of its sac-like body, with a slightly higher concentration around the mouth. They are responsible for reflexes involving longitudinal muscles at the base of ectodermal cells and latitudinal muscles at the base of endodermal cells by which hydra's tentacles wrap around prey that swim by and pull their paralyzed bodies into its mouth. There is a second and maybe a third network of neurons which enable hydra to throw its tentacles out in various directions seeking prey and to somersault to more favorable situations by attaching its tentacles to the ground and throwing its body over them. But it lacks extroªsensory organs (like all coelentrates), getting by with somatosensory input and phototropisms.

The flatworm has essentially the same structure as the hydra, except that one of the gradients that is perpendicular to the oral-aboral axis is a longitudinal gradient for the body. That is, it has a bilateral body with its mouth located near the middle of its ventral side. The bilateral body enables it to move about in space head first, and the head has primitive telesensory organs to guide it: Pigmented eye spots detect the direction of light and the motion of object and lobes on the sides of its head with mechanoreceptors and chemoreceptors detect the direction of water flow and detect certain kinds of molecules in it. Like the hydra, the flatworm has a nerve net throughout its body which coordinates the body with the pharynx as it feeds, but superimposed on it is a second nervous system, which is organized like a ladder along the length of the dorsal side of its body. At least two, and sometime four, six or eight nerve chords run in parallel from head to tail, with regular latitudinal nerves connecting them and innervating the muscles of the body. At the head, there are ganglia where neurons from the sensory receptors intersect with the longitudinal nerves, which trigger or repress the reflexes by which it moves. Both nervous systems are laid out in the gradients of its simple body. The nerve net centered around the mouth generates feeding behavior, whereas the longitudinal, ladder-type nerves centered at the head generates locomotion. The balance between them presumably selects the kind of behavior. (See diagram of Flatworm.)

The basic structure of the proterostome nervous system can be seen as a transformation of the flatworm nervous system that result from the evolution of gastrulation from the flatworm's planuloid development. On our speculation, the second layer of cells is formed by the "mouth-cells," which are located at the oral extreme of the oral-aboral gradient in the blastula. The mouth-cells lead the invagination of one hemisphere of the blastula that forms a second layer of cells, but they do not stop there. The invaginating endoderm does not seek out the aboral pole of the blastula to locate the anus; instead, it seeks out the tail in the longitudinal gradient of the ectoderm. The blastopore, which becomes the mouth, is also shifted from the middle of the ventral side toward the head, shortening the ventral side anterior to the mouth. Thus, the original oral-aboral gradient in the endoderm coincides posterior to the mouth with the longitudinal gradient of the ectoderm. This produces a new framework of gradients in which the nervous system is laid out. The result is a nervous system composed of a pair of nerve chords running along the ventral side of the body with one pair of ganglia connecting them anterior to the mouth and at least another pair of ganglia posterior to the mouth. (See diagram of Proboscis worm.)

If this is how to understand the evolution of gastrulation form the planuloid development of flatworms, we can see how proterostomes are trapped into a nervous system with two pairs of ganglia encircling the mouth. One pair is anterior to the mouth, the other pair posterior, and connections between them encircle the mouth. Reproductive causation has never extricated the nervous system from the mouth in any proterostome. As our speculation suggests, the reason is that the biological behavior guidance system uses gradients in the ectoderm to determine cells as neurons and gastrulation has organized those gradients around the mouth. With bilateral bodies, nerves apparently cannot be differentiated along the length of the body except symmetrically, in pairs. Although the parallel nerves are sometimes fused through most of the body of higher proterostomes, at the head, they still lie on either side of the mouth and are reconnected anterior to it.^ix

This structure is clearest in the simplest proterostomes, proboscis worms (Nemertina) and round worms (Aschelminthes). In higher proterostomes, such as mollusks (clams and squid), annelids (segmented worms), and arthropods (crustaceans, spiders and insects), the mesodermal coelom gives the body a more complex structure. The mesodermal coelom superimposes a structure on the gradients of the ectoderm and endoderm, which may modify the structure of the nervous system, but it does not enable the nervous system to avoid having two pairs of ganglia encircling the mouth.

The most radical effect of the mesodermal coelom is the segmentation found in annelids and arthropods. It results from a special kind of division of the mesodermal cells. After migrating into the space between ectoderm and endoderm, they divide into many pairs of stem cells. Each pair marks off a segment in the ectoderm, and after forming a solid mass of cells, each clump splits and forms a coelom with a complement of organs. Each segment is roughly equivalent to a gastrula, and the series is chained together, mouth to anus, as a continuous digestive tract. The segmentation they impose on the gradient in the ectoderm affects the structure of the nervous system. In most segments, there are only two main ganglia, which are connected along the ventral side by a pair of (fused) nerves, as if the pair of ganglia anterior to the mouth in each segment were suppressed. But at the head, the anterior segment, where the nervous system is centralized, there are still two pair of ganglia encircling the mouth, with the telesensory organs supplying input to the anterior pair. Thus, segmentation does not enable proterostomes to escape the trap of having at least two pairs of ganglia encircling the mouth. A far more radical change is needed to escape the ectodermal gradients left by gastrulation.

The deuterostome nervous system development. Deuterostome development makes it possible to lay out a centralized nervous system without encircling the mouth. Neurons still differentiate from the ectoderm, but the ectoderm from which they differentiate is a region that has separated from the outer skin and rolled itself up as a neural tube which is contained as a unit inside the body. The structure of the nervous system can be laid out free of the gradients of the gastrula because the neural tube uses gradients of its own to determine neurons to different kinds and connect them with one another. Since the deuterostome's embryological development is what makes this possible, that is where we begin.

Deuterostome development. Like proterostomes, deuterostomes develop by gastrulation, rather than by forming a planula. After cleavage, the daughter cells arrange themselves as the surface of a fluid-filled sphere, called the blastula. A second layer of cells is formed as one hemisphere invaginates and lines itself up along the underside of the remaining spherical surface. The outer layer of cells is the ectoderm; the inner layer of cells is the endoderm; and the hole through which cells have invaginated is the blastopore. Deuterostome development differs from proterostome development because the blastopore becomes the anus and the second opening becomes the mouth -- which is just the opposite of proterostome development. The animal has a longitudinal axis running from mouth to anus, and properly speaking, the endoderm marks the boundary between body and world no less than the ectoderm, for it becomes the digestive tract (and respiratory system in higher chordates) by which the body interacts with other objects in space, albeit under conditions that are more easily controlled. (See diagram of Gastrulation in amphiouxus.)

The body's internal structure depends on the next step in the process, which is also differs radically from the proterostome. Its task is a twofold. On the one hand, it forms a third layer of cells, or mesoderm, between the ectoderm and endoderm, and on the other, it forms a neural tube just beneath the surface of the dorsal ectoderm. The third layer of cells includes not only the coelom, from which muscles, a circulatory system and various other organs develop, but also the notochord, which is the precursor of the spine. There is a symmetry abut these two developments because at the end of gastrulation, the segment of endoderm from which the chordamesoderm develops lies just beneath the neural plate, the section of ectoderm from which the neural tube forms.

The notochord and mesoderm are formed by enterocoelous, a process of out-pouching by the endoderm into the space between the endoderm and ectoderm, which was originally the blastocoel. The cells involved are the "mouth-cells" that led the process of gastrulation by invading the blastocoel in the first place, and thus, enterocoelous is just a continuation of the cell movements that took place in gastrulation. Gastrulation first began on the dorsal side of the blastula, and a section of endoderm that runs the whole length of the gastrula along the dorsal side is involved in the out-pouching. This surface of the endoderm bends in toward the adjacent ectoderm, forming two sections of cells, both of which break off from the endoderm, allowing the rest of the endoderm to close behind it, thereby restoring the surface of the archenteron. The out-pouching cells become the mesodermal coelom on one side of the body, and a notochord forms where they meet along the midline. In fact, these out-pouchings become a series of segments, for they are divided into segments, like the notochord, which run the length of the body. They eventually spread out to form a complete layer of cells between the ectoderm and the remaining endoderm around the sides and along ventral side of the body.

The nervous system is formed by a similar out-pouching, but this time from the ectoderm. The cells involved are a section of ectoderm, the neural plate, that runs the length of the dorsal side of the gastrula just above the medial chordamesoderm. The neural plate separates from the ectoderm and sinks beneath the ectoderm. As the ectoderm closes behind it, restoring the outer skin of the body, the neural plate rolls itself up into a tube in the space between the ectoderm and chordomesoderm along the entire length of the body.^x (See diagram of Neurulation in amphiouxus.)

Ectodermal cells are determined to become part of the neural plate by the effect of the choradmesoderm on them during the process of gastrulation. And both the neural plate and chordamesoderm are segmented longitudinally in the process. That is, by the time the gastrula is formed, cells in different segments along the length of either structure have already been determined to become different kinds of cells. How this is accomplished is not known, but conceivably segmentation is induced by a pulse occurring during gastrulation that marks cells at regular intervals along its length as they invaginate. In any case, segmentation is a product of gastrulation, the process by which the "mouth-cells" form a second layer of cells in deuterostomes, not an effect of the special inner-gut cells from the primitive ectolecithal development, as in proterostomes. What is more, not only are cells located in different segments of the neural tube and mesodermal coeloms already different, but each segment has a 2-D gradient of its own in which cells can be differentiated.

The basic structure of the body at this stage is a set of tubes with the blastopore at one end and a mouth formed at the other. The outer tube is the ectoderm, and the innermost concentric tube is the endoderm. Filling the volume between them are several more tube-like structures: On the dorsal side is the hollow neural tube and just beneath it is the notochord. On each side of them lies a tube divided into a series of hollow areas, the coeloms. (See diagram of Crosssection of embryo of amphioxus.)

Although the segmented neural tube is the kind of basic structure that deuterostome development makes possible in the nervous system, it is of little use in the decentralized nervous systems at the somatosensory stage. There is a somatosensory deuterostome with a segmented neural tube, namely, Amphioxus, a cephalochordate. The sea squirt (a tunicate classified as an urochordate) also has a segmented neural tube at the larval stage. Even the rather primitive acorn worm (a hemichordate) has a neural tube, although it is not segmented.^xi However, the neural tube is not a universal feature of deuterostomes. It is not found in echinoderms, such as the sea star. The sea star has a solid nerve ring to control the tube feet in each arm, and, like acorn worms, there is also a nerve plexus lying underneath the ectoderm over the entire body. The nerve plexus is an apparently haphazard network of neurons, and the neural tube seems to be just a section of such a plexus that has been rolled up into a tube during development in most kinds of deuterostomes, including all telesensory deuterostomes.^xii

Independence of the nervous system. The most obvious advantage of separating the ectoderm from which the nervous system will develop from the outer skin is that it extricates the nervous system from the convoluted gradients of the ectoderm, which leaves proterostomes with two pair of ganglia surrounding the mouth. In the same way, it probably also enables reproductive causation to shape the body and its organs in whatever way that is useful in generating behavior without disrupting the nervous system, as it surely does in proterostomes with its ganglia and nerves running throughout the body. It also enables the nervous system to be divided into segments without the complete divisions of the body found in segmented proterostomes, since the segments are imprinted on chordamesoderm and neural tube by gastrulation, not by special mesodermal cells.

The unity that the neural tube gives the nervous system by contrast to the proterostome might well be compared to the contrast between the eukaryote and prokaryote behavior guidance systems. The prokaryote has a single loop of DNA attached to its cell wall, and the protein-DNA interaction that selects the kind of behavior occurs in the same space as the protein interactions that generate its behavior. In eukaryotes, DNA-protein interactions like those that guide prokaryotic behavior are contained within a nucleus, separate from the rest of the cell. Since its behavior is selected by an equilibrium involving an interaction of proteins and multiple chromosomes that is protected from interference by processes in the cytoplasm, eukaryotes can generate behavior on a higher scale than prokaryotes. Although the chordate is not on a higher level of natural organization from proterostomes, the neural tube, like the nucleus, does give the chordate nervous system a unity within the body that also enables it to generate behavior on an entirely new scale. Not only is the chordate nervous system not entangled with the organs generating the animal's behavior, but also when it is centralized at the second stages of zoological evolution, the processing required to select appropriate goals for the object and adjust its behavior to its spatial location can be carried out without interference by the rest of the body.

By separating the ectoderm which can differentiate into neurons from the rest of the body, the chordate has an additional step in setting up its nervous system: It must connect the nervous system to the sensory receptors and muscles in various parts of the body. The proterostome was spared this task by determining cells as neurons near the locations in the body where they would make their connections. But given the gradients that are established by gastrulation, it is a relatively simple task.

Although in Amphioxus, the connections between the neural tube and the body are made by processes from the neurons located in the neural tube, in the higher chordates, sensory cells (and neurons serving the viscera) derive from the neural crest. The neural crest is a group of cells that breaks away from the edge of the neural plate before it forms into a tube and individual cells migrate to locations in the body. In either case, the neurons that connect the neural tube with the body can easily find their targets. Not only does the ectoderm as a whole have a 2-D gradient of messenger molecules, but segments are also marked off in it by the segmentation of the mesodermal coelom. Given how segments are imprinted, mesodermal segments surely correspond to segments of the neural tube (and neural crest), enabling the same gradient mechanisms to be used in making connections at both ends. Neurons may even use the 2-D gradients set up within each mesodermal segment to locate the precise muscle or gland cells to which they will connect or to distribute their connections with internal organs evenly.

Neurons born in 2-D arrays. The advantages that a neural tube affords a centralized nervous system have been described negatively, as overcoming the deficiencies in proterostome nervous systems that derive from using the ectodermal gradients to lay out its structure. But positive advantages are what make higher levels of neurological organization possible. The 2-D gradient in which neurons can be determined to special kinds and make connections with one another are supplied by the neural tube. That is, since neurons are born with labels indicating their segment and 2-D location within that segment, there is no need for neurons to multiply and set up their own gradient to become neurons of specific kinds, as ganglia do.

Each gradient, we have assumed, involves a pair of messenger proteins, with one being concentrated at one extreme along its direction and the other being concentrated at the opposite extreme. The location of any cell in any gradient is indicated by their relative strength, and thus, the location of a cell in the neural tube is indicated by its location in two gradients: one in the longitudinal direction, and one that extends from the ventral midline of the neural tube to the dorsal midline where the two sides of the neural plate closed. Indeed, there are two sets of these 2-D gradients in the neural tube, since each half of the bilateral body would be a mirror image of the other. The third gradient, extending from the central canal of the neural tube to its outer border, is used to guide neurons in migrating and making connections, but not to determine neurons to specific kinds. Furthermore, since the neural tube is divided into segments along its length, the cells in each segment are different from those in other segments. And with each segment having its own 2-D gradient, it is easy to see how complex interconnections can be set up.

Suppose that once the gradients are established in each segment, each cell somehow records the relative strength of each pair of messenger proteins in which it finds itself. Some cells that are differentiated throughout the neural tube remain there; as they elongate, labels from the original gradient are posted, and these processes enable other cells to find their way about. They are called "glial" cells. At an earlier stage of development, cells of the neural tube are determined to become neurons. Neurons always divide at the inner surface of the neural tube bordering on the central canal.^xiii When they send processes or migrate to other locations, they can easily line themselves up in a 2-D array with other cells from the same segment, because they can use the labels from their original locations in the neural tube to seek out the place where the balance between the messenger proteins of cells on one side is greater and on the opposite side less than their own. Or when processes arrive at another segment, they can superimpose themselves in a regular way on the cells already located there by seeking out their own location in the gradients of local cells. In short, entire 2-D arrays of neurons from one segment of the neural tube can be connected with 2-D arrays of neurons in other segments in a regular, topographical way. Indeed, that is what every neuron from a segment would do, unless they were differentiated from one another.^xiv

Vision is a good example of the advantage of the 2-D arrays built into the gradients of the neural tube. The retina of the eye derives in development from a section of the neural tube that migrates as a whole to the ectoderm and determines cells located there to become a lens and an eyeball surrounding it. The neural tube's gradients supply each neuron in the retina with information about its location in a two-dimensional matrix. Thus, their axons are able to keep their order as they project back to the neural tube. The optic nerve is a single cable, often containing millions of axons, and labels from their built-in gradients enable them to keep line up, even when the two optic nerves merge and the axons from half of each retina are sent off in a different direction. And they can easily superimpose themselves in an orderly way on 2-D arrays of neurons from other segments, which are their targets.

The contrast to the proterostome nervous system could not be starker. Cephalopods, such as squid and octopus, have camera-type eyes which are the equal of vertebrates, but their nervous systems is a collection of ganglia that are arranged around the mouth. The eyes feed sensory input to the optic lobes, which connect with other lobes, and behavior is guided by the equilibrium reached by an interaction that depends on the equilibria reached in each of various lobes. Visual input is conveyed by the configuration of firings in 2-D arrays of neurons, but in order to operate a camera-type eye, cephalopods must build up complex 2-D arrays of neurons within special ganglia in order to carry the information. A glance at the basket-weave of the optic nerve in the octopus makes it clear that a good part of the biological behavior guidance system's machinery for differentiating cells is used up simply keeping them straight as they project to the target. That is, a kind of structure that is very near the limit of what the proterostome development can accomplish is supplied by deuterostome development at the outset as the foundation on which further structure is constructed.

Although the somatosensory nervous system gets by with single neurons serving the functions of registering input, generating output and selecting between kinds of behavior, the telesensory nervous system requires at least one 2-D array of cells for vision and a centralized system to make use of it. Proterostomes and the chordates among deuterostomes are both capable of these two levels of natural organization in the nervous system. As I have mentioned, however, the third animal stage of evolution requires complete circuits of such 2-D arrays which can interact with one another as units to register input and generate output. The fourth animal stage involves the interaction between various channels through both input and output circuit of 2-D arrays. The machinery required to connect 2-D arrays of cells from ganglia is so complex that it is not possible for these mechanism to evolve as variations on the proterostome nervous system. But deuterostome development makes possible a neural tube that supplies labels to cells by which entire 2-D arrays of neurons are connected with relative ease. In chordates, therefore, a third level of neurological organization can occur as a variation on the second level, and a fourth level can occur as a variation on the third level. Given the possibility of higher levels of neurological organization, reproductive causation inevitably makes them actual. Thus, our interpretation of embryology gives us an explanation why a third and fourth stage of zoological evolution occurs in deuterostomes, but not in any proterostome.

5. Telesensory animals. Telesensory animals are multicellular animals with a centralized nervous system in which the three basic subfunctions of the animal behavior guidance system are served by entire systems of neurons. They include most invertebrates along with non-mammalian vertebrates, and after explaining why the basic structure of the invertebrate nervous system limits their subsequent evolution, this chapter describes the structure of the vertebrate brain in detail and traces the actual evolution of vertebrates on earth. But in order to deduce this stage of evolution, it must first be shown to be inevitable.

Inevitability of telesensory animals. According to this ontological explanation of evolution as a global regularity, the evolution of multicellular animals with nervous systems at the telesensory level of part-whole complexity is inevitable, if it is both possible and functional.

Possibility. To be possible, the telesensory level of neurological organization must fall within the range of random variations being tried out in the evolution of somatosensory animals. And it is clearly possible, because somatosensory animals already have already evolved the mechanism of embryological development to serve as their biological behavior guidance system, and they have already evolved neurons for transmitting and regulating the signals from sensory input that caused behavioral output. Thus, all that was required for telesensory animals to evolve was a higher level of part-whole complexity in the organization of the nervous system, that is, a centralized nervous system in which neurons are organized into systems that can serve the basic subfunctions of an animal behavior guidance system with an animal system of representation.

Neurons generating motor output must be parts of a single system, in order for animal behavior to include locomotion in relation to objects at a distance. But since local reflexes in somatosensory animals could already recruit one another to generate whole body behavior, control of locomotor behavior could be supplied by neurons that controlled all the local reflexes.

However, in order to guide locomotion relative to distant objects, sensory organism must be able to detect objects located at a distance from the body, and since that means using proximal input to extract information about distant objects, neurons must be organized on a higher level of part-whole complexity in space. There are only certain kinds of effects on the animal’s body that can be used: electromagnetic radiation, vibrations in the medium or substratum, and kinds of molecules encountered. But since somatosensory animals have already evolved neurons that respond to such effects, it is just a matter of organizing them into systems of neurons whose joint output depends on the distant objects causing the proximal input.

In the case of vision, for example, photo-sensitive neurons must be arranged in a two dimensional array (2 .D array). Not many such neurons are required for the compound eyes of insects, but in camera-like eyes. extremely large 2 .D arrays of neurons are required to register images focused on them by a lens. Hearing requires only neurons that are sensitive to mechanical disturbances, but to discriminate the direction and tone of the sound, they must compare the disturbances of many neurons at once. (Hearing evolve in vertebrates from the lateral line in fishes, which is basically a series of sensors of mechanical disturbances along the side of the body.) Though somatosensory animals already have cells sensitive to kinds of molecules (taste receptors) by which they choose which objects to ingest, olfaction requires a large variety of neurons testing many different aspects of the shapes of molecules at the same time. In each case, multiple neurons are organized as a whole system, and the effects of its geometrical structure are as important to the function of the telesensory organ as the kind of neuron of which it is composed.

These systems of neurons had to be organized as parts of centralized nervous system in order to use telesensory input to guide locomotion (and to select the appropriate kind of behavior as an animal behavior guidance system). And as we have seen, in order to construct an animal representation for guiding behavior in relations to distant objects, brain mechanisms must connect input from telesensory organs with input from their bodily condition, such as the orientation of the body and head and its locomotion. But since the mechanism of embryological development had evolved to construct structures of eukaryotic cells, there is no reason to doubt that the telesensory nervous system is possible.

Functionality. To be functional and begin another stage of evolution, however, such a higher level of neurological organization had to enable telesensory animals to control an entire range of relevant conditions that were out of reach for animals at previous stages.

Though it is clear that the ability to use telesensory input would make them more powerful than somatosensory animals, it may not be clear that this power was out of reach for all previous animals, because animals at lower biological levels move about and have mechanisms to guide their locomotion.

Magnetosomes in bacteria, for example, tell which direction to move in order avoid the toxic effects of oxygen-rich water near the surface. And animal-like protists, such Paramecia, have eye spots by which they can orient their motion relative to light.

However, even if this is the capacity to guide locomotion relative to distant objects, it would make telesensory animals inherently more powerful, because they would be guiding the locomotion of a multicellular animal, which is already inherently more powerful than single-celled animals.

In any case, these structures in animal-like protists are not telesensory organs, much less an animal systems of representation, because they do not detect objects at a distance in space. They merely orient locomotion in some ambient field. In these animals, locomotion is just a response to light built into the organism’s structure by the biological behavior guidance system, like reflexes in somatosensory animals.

Since telesensory animals are both possible and functional, this ontological explanation of revolutionary evolution implies that their evolution is inevitable. Telesensory animals would evolve on any planet in a spatiomaterial world like ours where stages of evolution could unfold at all. But since they begin another stage of evolution, reproductive causation also implies that their basic power to guide locomotion in relation to distant objects would evolve in ways that enable them to control additional conditions affecting reproduction. This prediction is confirmed by the main accomplishment of this animal stage of evolution, namely, the evolution of nervous systems with the capacity to map the relations of salient objects in their territory.

Maps. Telesensory animals would be even more powerful, if besides guiding locomotion in relation to objects currently being detected objects at a distance, their animal representations enabled them to guide locomotion in relation to currently undetected objects. Since telesensory nervous systems must already be able to generate more or less complex instinctive behavioral routines in relation to objects in space in order to generate the various kinds of behavior needed to control relevant conditions, only relatively modest modifications of their neurological mechanisms are needed to represent the locations of unperceived objects.

For example, the capacity to keep track of how far the animal moves in each direction relative to the sun or magnetic north would enable it to return to a nest by "dead reckoning" (so that once it is in the vicinity of its nest it could guide its locomotion relative to objects recognized from current telesensory input). Gallistel (1990) has marshaled abundant evidence of such mechanisms in telesensory animals. Desert ants, for example, find their way back to their hive by keeping track of how far they go in any direction relative to the sun or wind. Only when they get in what should be the vicinity of their hive do they orient their locomotion by telesensory input from objects in space. (Gallistel 1990, pp. 59-65.)

The use of large-scale maps by social insects like honey bees is undeniable. Returning foragers direct other members to energy sources by performing a figure-eight dance in relation to the azimuth of the sun that successfully communicates both the direction and distance to other bees. Gallistel shows how these feats could be explained rather simply, assuming that neural mechanisms can represent distances and directions of locomotion and perform quantitative computations on them.

Such telesensory level animal systems of representation are capable of rather sophisticated navigational feats. When honey bees, for example, are released in a region with a known bearing and distance from their hive, not only can they return to their hive, but they can also fly directly to another, unseen energy source with a different bearing and distance from their hive when they have recently been feeding on it and that is the only way to obtain energy (Gallistel 1990, pp. 131-140).

Such territorial maps suggest how much power can evolve in telesensory animals because their animal behavior guidance system contains a system of representation. But to call a mechanism a system of “representation” is to say that there is a correspondence between its representations and what they represent, and it is relevant to consider how such a correspondence is constituted by the animal system of representation, because it is the beginning of an explanation of the nature of truth that will hold of rational beings like us as well.

In the case of the simplest animal systems of representation, the correspondence is basically geometrical. Spatial aspects of behavior are adapted to spatial aspects of the world so that the behavior imposes a geometrical structure on the thermodynamic flow in the region, and what makes that possible is an implicit correspondence between the representation of the object in the animal system of representation and spatial aspects of the world. The representation of the object in the sensory input system has a geometrical structure that corresponds to the relations of objects in space because of how sensory input is recorded together with input from the current bodily condition.

Telesensory organs, like the eye, provide information about the locations and kinds of objects, not only because of the interaction between the eye’s geometrical structure and other objects in space (by way of photons), but also because that telesensory input is contingent on the direction in which the eye is pointing and the head is oriented. Telesensory input is registered in a way that reflects the bodily condition at the time, and since the animal representation can trigger behavioral dispositions that will approach or avoid objects at a distance, it can be used to guide locomotion in relation to them.

The basically geometrical nature of the correspondence between the animal representation and the locations of objects relative to the body solves a problem that functionalist explanations encounter when they try to explain correspondence with nothing but causal connections between input and output within the organism. The correspondence is not just a constant conjunction between telesensory input and the object in space that is involved in reference, as Fodor seems to mean by calling it a “casual connection,” but an isomorphism between a structure in the brain and the geometrical structures about the locations of objects in the space around the telesensory animal. (See Epistemological philosophy of causation: Rational causation: Psychology: Naturalism.)

In the case of maps of the spatial relations of unperceived objects in the territory, the correspondence depends on a more complex geometrical structure than is required to represent the locations of currently detected objects in space, because it involves two phases.

First, since the animal representation of the object functions as a map, telesensory input must be registered in a way that reflects how far the animal must go in certain directions relative to the sun or magnetic north to get from one recognizable location to another. (This is a form of inquisitive behavior.)

Once the map has been constructed, the animal can, during the second stage, use the isomorphism between those brain states and salient objects in the territory to guide its behavior in relation to undetected objects in space.

The construction and use of maps are two different structural global regularities generated by the structure of the nervous system. During the map-making phase, the nervous system acquires an additional geometrical structure from the world, and during the second phase, it uses that unchanging geometrical structure to guide its behavior. The world itself is, therefore, partly the source of the structural cause by which animal behavior imposes a geometrical structure on the thermo­dynamics flow of matter in the region toward evenly distributed heat. The use of its map enables the animal to anticipate what will happen as it moves in various directions so that it can choose among them according to the kind of behavior that would control relevant conditions. This geometrical fit of its behavior with the environment would be quite mysterious, except for the structural causes involved, including the first phase of map-making behavior that sets up the correspondence involved in representing the locations of salient objects in its territory.

The Inferiority of Invertebrates. The evolution of telesensory animals in the direction of natural perfection for organisms of their kind is necessary for the evolution of subjective animals, but it is not sufficient. The telesensory stage must make it possible for the mechanism of embryological development (the biological behavior guidance system for multicellular animals) to try out, as a random variation, the higher level of neurological organization required for locomotor imagination. Its possibility is clearly not a foregone conclusion. Indeed, it happened in only one kind of telesensory animal, the vertebrates. It did not happen in invertebrate animals.

It is because vertebrates seem so basically different from other animals that all the other animals are usually classified together as "invertebrates". It has long seemed that vertebrates have a greater capacity for evolution. They generally have larger and more powerful bodies, not only those that live in water, but also those on land and in the air. The closest invertebrates come to approximating the vertebrate animal system of representation are the octopus and squid, which have evolved the same kind of camera-type eyes (focusing images on a retina) that vertebrates of all kinds have.

However, many kinds of invertebrates, including insects, many mollusks, and even worms, are in the same category of natural kinds as sharks, fishes, amphibians, reptiles, birds and even dinosaurs. All are telesensory animals, with centralized nervous systems and the capacity to guide behavior in relation to objects at a distance. And map-making powers evolve in both classes of animals. Though the examples mentioned above are invertebrates, similar map-making capacities have been demonstrated in telesensory chordates, such as fish, reptiles and birds (Gallistel 1990, Chapters 4 and 5).

There is a similar difference between two classes of somatosensory animals, even those whose radial bodies indicate their adaptation at this level. There are simple somatosensory animals, which include the hydra, jellyfish, sea anemones and corals (coelenterates) and their somewhat more complex cousins, the comb jellies (ctenophora). But there is another kind of radially symmetrical animal that is far more complex, the echinoderms, including sea stars ("starfish") and sea urchins. The difference in their complexity does not come from their stage of evolution, since they are both kinds of somatosensory animals. (But it is explained, as we shall see, in the same way as the difference among telesensory animals.)

The difference in the fates of these two classes of animals poses a challenge to this ontological explanation of revolutionary evolution. If evolution is really a dialectic of gradual and revolutionary change in which stages of evolution follow one another in time, then why did the next stage not happen to any invertebrates species? Thus, let us consider what makes vertebrates so different from invertebrates before we show how the vertebrate nervous systems evolves a higher level of neurological organization.

The answer to this puzzle is found in their patterns of embryological development. There are basically two different ways that multicellular animals develop, and it has long been recognized as a basic difference among them. Once class has so-called “proterostome” development, whereas the other has “deuterostome” development. Deuterostome embryological development in vertebrates and how it differs from proterostome development will explain what makes it possible them to try out higher levels of neurological organization. The origin of this difference was explained, along with a more detailed description of the difference between proterostome and deuterostome nervous systems, in Stage 4: Origin of the mechanism of embryological development.

Since every cell in a (sexually reproducing) multicellular animal derives from the same fertilized egg cell and has the same genetic structure, the basic challenge in constructing a complex body or nervous system is to make the cells become different in their behavior and yet coordinate them so that they work together as a whole. This challenge has been met by a process called embryological development, which began with the original multicellular animals of this kind and became increasingly elaborate through evolution.

Sexual reproduction requires, as we have seen, that the whole body of the multicellular animal be constructed from a single fertilized egg cell, and this mechanism coordinates the lower level organisms of which multicellular animals are composed. This is a function of what is classified here as the "multicellular biological behavior guidance system."

The advent of that important mechanism is responsible for the Cambrian revolution, which marks the very beginning of the fossil record some 600 million years ago. That is when the fossils of many different species of multicellular animals suddenly showed up, and since fossils form only when multicellular animals evolved hard parts, like shells, it indicates roughly when the mechanism of embryological development first evolved. That is the mechanism that constructs the nervous system.

Cells are first determined to become different kinds by the part of the cytoplasm (or cortex) of the fertilized egg that they inherit from the initial divisions of the egg cell. But animals need complex bodies in order to act on other objects in space, and that requires a developmental process in which some cells (and groups of cells) move past other groups of cells that remain attached to one another. What made it possible for animals to have a form of embryological development that is so different from plants is the animal-like behavior of the protists from which animals evolved (presumably, amoebas), including locomotion. Except in the simplest animals, development involves a process of gastrulation, and early in that process, a major difference shows up among multicellular animals, indicating an early branching in the evolution of their kinds. It separates vertebrates from most kinds of invertebrates, and it explains why vertebrates are able to evolve higher levels of neurological development, beyond telesensory animals, whereas invertebrates cannot.

The major division among animals is the difference between proterostomes and deuterostomes. Most invertebrates are proterostomes, but vertebrates are deuterostomes. A brief sketch of the difference about the basic frameworks in which their nervous systems are laid out will make it clear why higher levels of neurological organization occur only in vertebrates.

In proterostomes, the basic structure produced by gastrulation is a single tube formed of two layers of cells (ectoderm and endoderm) stretching between the mouth and anus. There are apparently gradients of messenger proteins established in the tube as a whole, uniquely identifying every location in it. Although the mechanism has not yet been fully explained, the multicellular behavior guidance system can apparently address cells by their locations in this gradient, make them open up different segments of their chromosomes so they behave differently, and thereby enable them to move past other cells to other locations in the body which are also identified by this gradient. In proterostomes, this is the source of the structure of both the nervous system and most of the structure of the body. Neurons always develop only from the outer layer of cells in the tube (ectoderm). Cells located in certain parts of the two-layered tube are determined to become ganglia, which are clusters of neurons that set up their own gradients of messenger molecules among themselves. And the multicellular behavior guidance system can also use these new gradients, within the ganglia that form, to address cells individually and make them send axons to connect with certain other neurons in the same ganglion or to certain neurons in other ganglia located elsewhere in the body.

In deuterostomes, gastrulation is able to produce a basically different structure of gradients for the multicellular behavior guidance system to use in determining cells, although not all deuterostomes exploit this capacity. There is at least a 2-D gradient in the tube extending from mouth to anus identifying the locations of cells (with cells also orienting themselves orthagonally to the surface of the tube), and there is an additional body-length tube, the neural tube, with a similar 2 .D gradient of its own, which becomes the spinal chord and brain in vertebrates.

The neural tube is formed from a body-long strip of the outer layer of cells (or ectoderm) of the body-tube (or gastrula) which folds over and sinks beneath the outer layer of cells. Although neurons still develop only from the ectoderm, the ectoderm used in deuterostomes is the neural tube, and its separation from the rest of the body enables the multicellular behavior guidance system to use the 2-D gradients in the neural tube to address neurons separately from the cells that become other parts of the body.

Furthermore, during the process of gastrulation in which the neural tube is formed, both the body and the neural tube are segmented, so that there is actually a series of 2 .D gradients (including a difference between right and left sides of the body) running along the length of both the body and the neural tube. Thus, not only are all the cells of the behavior guidance system already separated from the rest of the body in a tube with their own 2 .D gradient, but that all .inclusive 2 .D gradient is also subdivided regularly into smaller 2 .D gradients. The animals that take advantage of deuterostome development to construct a nervous system in this way are all called "chordates".

Since the challenge to the mechanism of embryological development is to coordinate the behavior of lower level organisms, it is clearly an advantage to have a segmented neural tube in which to construct and operate the animal behavior guidance system separate from the rest of the body. Indeed, there is a useful analogy to the biological behavior guidance system. Chordates seem to have a higher level of organization than proterostomes in a way that resembles how eukaryotes differ from prokaryotes, although chordate and proterostome nervous systems are actually on the same level of part-whole complexity.

The prokaryote and eukaryote biological behavior guidance systems both coordinates the behavior of segments of DNA (or genes) in much the same way as the multicellular animal behavior guidance system coordinates the behavior of neurons in both proterostomes and chordates. The lower level organisms are coordinated by being parts of the structure of the organism as a whole. But prokaryotes are to eukaryotes as proterostomes are to chordates.

In prokaryotes, a loop of DNA, containing all the genes, is located alongside all the other molecules in the cell, whereas in eukaryotes, multiple chromosomes are kept separately in a nucleus, where the expression of all their genes can be coordinated without interference from the mechanisms generating the behavior of the cell as a whole.

Likewise, in the case of nervous systems. In proterostomes, neurons are determined to become ganglia from the body's 2 .D gradient alongside all the other organs of the body, whereas in chordates, the only cells that become neurons come from the 2 .D gradients of a segmented neural tube, so that the coordination of cells in setting up the nervous system is not disrupted by the coordination of cells in setting up in the body.

In both eukaryotic cells and chordates, there is a spatially distinct organ for controlling the simplest units involved in guiding behavior. It is important to recognize, however, that deuterostome development does not put chordates on a higher level of part-whole complexity than proterostomes. It does not make much sense to talk about levels of part-whole complexity when there are only two levels.

There is, moreover, a further advantage in separating the animal behavior guidance system in the neural tube from the rest of the body. In proterostomes, where there is no such separation, another set of gradients has to be set up in each ganglion to coordinate its neurons after the ganglion has been determined from the ectoderm. In chordates, by contrast, this step has already been accomplished before neurons are determined, because cells in the neural tube already contain labels indicating their relative locations in the local 2 .D gradient of each segment of neural tube as well as their segment relative to other segments in the neural tube as a whole. The chordate multicellular behavior guidance system can, therefore, address whole 2 .D arrays of cells in a segment at once and tell (some of) them (from each local area) to migrate to, or to send axons to, another 2 .D array in the neural tube, while keeping their relative positions in their own 2 .D structure and finding their counterparts in the target array. That is, chordates have 2 .D arrays located in a more inclusive 2 .D array. Thus, it is as if the units supplied by gastrulation for use in neural development were not just single neurons, but also whole 2 .D arrays of neurons.

This difference would explain why only vertebrates are able to try out yet higher levels of neurological organization, and we shall see why such connections among whole 2 .D arrays of neurons are essential to the mechanisms of the subjective animal system of representation that gives mammals a locomotor imagination. It will not be known precisely how the segmented neural tube gives vertebrates such an advantage until the mechanisms of the multicellular biological behavior guidance system are explained, but that is not essential to this argument, for it depends only on recognizing a basic difference between the biological behavior guidance systems of proterostomes and deuterostomes in how they coordinate the behavior of cells in setting up the structure of the nervous system.

The difference between a nervous system enclosed in a separate unit and one spread throughout the body is intuitively clear, and there are many reasons for believing that this accounts for the failure of invertebrates to evolve higher levels of neurological organization are not hard to find. Here are three (which are explained in more detail in Stage 4: Multicellular organisms: Evolution of embryological development).

First, it is clear that the gradients in the body of invertebrates could interfere with the structure of the nervous system, because, despite the obvious advantage to telesensory animals of having a nervous system centralized in the head for guiding locomotion, not a single proterostome has managed to disentangle its nervous system from the mouth itself. At the head of every telesensory proterostome, there are always two pairs of ganglia whose connections encircle the mouth. This reflects the gradients set up in the body by proterostome development, in which the mouth is the opening in the sphere created by gastrulation. Proterostome development is simpler than deuterostome, but it compromises the unity of the centralized nervous system.

Second, although proterostomes do develop segmentation in their bodily structures (in segmented worms and insects), it does not give the nervous system a larger 2 .D gradient in which smaller 2 .D gradients are embedded for use in connecting 2-D arrays at different locations with one another, because it is the body as a whole that is segmented. The body is, in effect, a series of simpler, proterostome bodies. Ganglia can be set up in each segment, but they still have to set up their own internal 2 .D gradients. Hence, they are independent of one another and not coordinated with one another by being embedded in a larger 2 .D gradient.

Unlike the deuterostome development of chordates, where the process of gastrulation segments both the body and the neural plate (which becomes neural tube), the segments in proterostomes are set up by the duplication of special mesodermal cells, which give rise to coeloms that divide the basic tube-like structure of their bodies.

Third, the evolution of a camera-type eyes in the squid and the octopus shows that the difference between invertebrates and vertebrates cannot be explained by any lack of ability to evolve the right kinds of cells. But the difference in their wiring does show the advantage of having 2 .D arrays built into the gradients of the neural tube. In vertebrates, the retina of the eye develops from a section of the neural tube that migrates as a whole to the ectoderm (where they determine cells located there to become a lens and an eyeball surrounding it). So their axons, with millions of them in a bundle, are able to keep their spatial relations to one another as they project back to the neural tube and superimpose themselves in an orderly way on the 2 .D arrays of their targets. But in order for the octopus, as an invertebrate, to operate a camera-type eye, the complex 2 .D array of cells must be constructed from the neurons in ganglia, and whatever is going on, a glance at the basket-weave structure of its optic nerve makes clear that it takes a good part of the multicellular biological behavior guidance system's capacity for determining cells simply to keep them straight as they project to their targets. Not surprisingly, it is not easy to combine many such neural mechanisms as parts of a larger neural mechanism. (See Diagram.)

By explaining why invertebrates are unable to try out higher levels of neurological organization, we also explain why vertebrates do. Deuterostome development coordinates lower level organisms in a way that can set up a segmented neural tube separate from the rest of the body so that it can then use all its powers of coordination to set up the nervous system and only later connect it with the body (using its parallel set of segmented 2-D gradients).

Vertebrates also differ from invertebrates, of course, in having generally larger and more powerful bodies. That has not been explained. Nor will we try to explain it, except to suggest that, since their size and power are mainly a matter of having an internal skeleton, rather than an external skeleton (as in insects) or no skeleton at all (as in the octopus), and since the vertebras are also determined as a separate unit running the whole length of the body (the notochord) in the same process of gastrulation and segmentation that determines the body and the neural tube (and the coelom, from which the internal organs come), it would not be surprising if the same cause were responsible for this other difference from invertebrates as well.

The structure of the non-mammalian vertebrate brain. In the non-mammalian vertebrate brain, the three systems serving the main subfunctions of the animal behavior guidance system are located in three anatomically distinct parts of vertebrate brains. It is relevant to take account of this structure, because shifting the sensory input and behavioral output systems to the part of the brain that served only the goal selection subfunction in non-mammalian vertebrates is the random variation that will try out the higher level of neurological organization found in the mammalian brain.

Basic structure. In the non-mammalian brain, the major systems and their functions are obvious, given the function of the animal behavior guidance system (and its three subfunctions). The brain itself is one of two main components of the nervous system set up in the neural tube.

The other component is the spinal chord. It is the entire nervous system of somatosensory chordates (represented by Amphioxus) from which vertebrates evolved. For vertebrates, the spinal chord serves mainly to connect the brain with the rest of the body.

In the brain's segment of the neural tube, embryological development results in three, anatomically distinct parts: just above (rostral to) the spinal chord is the hindbrain, followed by the midbrain, and finally (at the rostral-most end) the forebrain. These three units can be explained by the three subfunctions that any system that would choose among different kinds of behavior must have. Any behavior guidance system, as we have seen, must register input from the world, select from among incompatible kinds of behavior, and generate the kind of behavior chosen. That holds for the vertebrate brain. These three subfunctions account for the kinds of neural connections found in the hindbrain, midbrain and forebrain, as a brief sketch of their connections will confirm. (See the diagram of the main parts of the non-mammalian brain.)

Furthermore, the neural connections among these sub-systems are just what would be expected of an animal behavior guidance system with an animal system of representation, that is, with input from the bodily condition being combined with telesensory input to construct an animal representation of the object that can guide locomotion in relation to distant objects.

Hindbrain’s behavioral output system. The hindbrain is responsible for motor output to the body. In order to guide locomotion by telesensory input, the hindbrain takes over control of local reflexes in all segments of the original neural tube (as in Amphioxus), and thus, the somatosensory input that triggered those local reflexes is also passed toward the head (rostrally) and registered in the hindbrain. (See diagram of the behavioral output system.)

But the hindbrain does not represent the body somatotopically, that is, as a picture or isomorphic representation of the body. (Its diffuse organization is called a "reticular formation".)

There is, however, an appendage to the hindbrain, the cerebellum, whose neurons correspond roughly to the geometrical structure of the body because of how it assists in generating behavior. The somatotopic organization is required by the cerebellum's function. It modifies the hindbrain's motor output in order to even out the spatial distributions (and temporal sequences) of its ultimate commands to local muscle groups (using its own somatosensory input).

That is, when different regions of the hindbrain generating different kinds of behavior call on the same local muscle groups in the spine, the cerebellum distributes their orders spatially and temporally so that all the tasks requested are accomplished without overtaxing any local group (while keeping the body oriented in gravity, with the help of the vestibular nucleus). It has its own channel of sensory input from the body, from the inner ear about acceleration and orientation in gravity, and from nuclei (olivary nuclei in the caudal hindbrain) that appear to compare motor commands with somatosensory input. It modifies motor commands by way of its output to the hindbrain behavior generator.

Midbrain’s visual input system. The midbrain registers telesensory input from the object. The main form of telesensory input was originally vision, whose 2 .D arrays, as mentioned before, are easily set up in the neural tube. The retina is a segment of the forebrain that migrates to the ectoderm of the body and determines cells already located there to become a lens and an optic cup behind it. The retinal neurons send an ordered, 2 .D array of axons to a region of the midbrain called the "optic tectum" (and to a part of the forebrain called the "thalamus" from which the retina migrated). (See diagram of the visual input system.)

The optic tectum picks objects out from the background, a relatively easy task when either the object or the animal is moving. Its control of the direction of the eye serves the function of inquisitive behavior in the animal system of representation, though the optic tectum also receives some somatosensory input. But somatosensory input includes the "lateral line" in fishes, which can detect the pressure caused by fish swimming nearby, and there is also taste input to the optic tectum (from cranial nerves that serve the feeding apparatus), and hearing (after it evolves).

The optic tectum has a large projection to the hindbrain behavioral output system, by which the optic tectum can adjust locomotion according to the direction, motion and distance to the object in space it is tracking visually and direct routine responses to objects, as in feeding. In non-mammalian vertebrates, in short, the optic tectum serves as the animal representation, or the input subfunction in the animal system of representation, for it guides the locomotion of the body in relation to the currently perceived object.

Forebrain’s olfactory selection system. The basic need responsible for the evolution of the behavior guidance system is choosing the goal, and telesensory animals must choose which goal to pursue with respect to the object at a distance (feeding, self-protection, mating, and the like). This subfunction is served in non-mammalian vertebrates by the forebrain.

In the primitive vertebrate brain, these decisions depend mainly on the forebrain's own form of telesensory input, olfaction. The olfactory bulb, located at the extreme rostral end of the telencephalon, contains neurons that identify molecules by interacting with them directly. About organisms, olfaction is usually a reliable indicator of the kind being encountered. The olfactory bulb has multiple pathways by which it reaches the midbrain and can control the kind of behavior that the hindbrain generates in response to the visual input from the object. (See diagram of the olfactory selection system.)

One pathway by which the olfactory bulb affects the midbrain is through the hypothalamus, a (ventral) part of the diencephalon, which has multiple connections to the midbrain. A second pathway is through the amygdala, another nucleus in the telencephalon, which, as the seat of fear, can override other routines and generate fighting or fleeing instead. And there is a third pathway involving the septum, a ventral part of the telencephalon.

In primitive vertebrates, the main route for affecting the midbrain is via the habenulae, a prominent, asymmetric pair of nuclei located just above the diencephalon (or atop the dorsal thalamus) which has a heavily myelinated bundle of fibers (the fasciculus retroflexus) that passes through the thalamus to a spiral shaped nucleus at the ventral midline of the midbrain (the interpeduncular nucleus). The olfactory bulb projects to the hypothalamus and the septum (which are interconnected), and they have connections to the habenulae via the stria medularis. The amygdala (which is also connected to the hypothalamus) has a connection of its own to the habenulae via the stria terminalis. (See diagram of the olfactory selection system.)

The forebrain also has, as we shall see, two other ways of affecting motor output, which depend on other kinds of sensory input. The forebrain receives (via its thalamus) visual input (both indirectly, by way of the optic tectum, and directly, from the retina), auditory input (after hearing evolves), and even some somatosensory input, all of which become increasingly pronounced in the evolution of vertebrates. (See diagrams of the forebrain output.) But these sensory inputs are used only to modify behavior in relation to distant objects currently being detected by the optic tectum and to generate complex instinctive routines, including telesensory map-making routines. Thus, there are, including olfaction, three ways that the forebrain can influence what happens in the midbrain and hindbrain, and all have to do with the subfunction of selecting the right kind of behavior.

Foundation for a higher level of neurological organization. Looking ahead, the transformation of the non-mammalian into the mammalian brain is often described as the centralization of functions in the nervous system. That is, as mentioned above, the three subfunctions of the animal behavior guidance system, which are parceled out to the three anatomically distinct sections of the non-mammalian brain, are all served by one of those sections in mammalian brains, namely, by the forebrain. The midbrain and hindbrain structures are still there, but they are slaves to the forebrain. The simplest and most convincing way to show how the four subsystems of the subjective animal system of representation are the functions served by structures in the mammalian forebrain will be to describe how those structures evolve from simpler mechanisms in the non-mammalian forebrain, and thus, it will be helpful to describe the relevant structures of the vertebrate brain here.

There are two important kinds of changes in the mammalian brain, not only the evolution of a neocortex, but also the redirection of erstwhile forebrain output back to the forebrain (by way of the thalamus) to form the complete circuits of its higher level of neurological organization. To see what is involved in these changes, let us look at the structure of the non-mammalian forebrain more closely and its three outputs to the midbrain.

Embryological development of the forebrain. The vertebrate forebrain develops from the extreme rostral section of the neural tube. It has two parts, the diencephalon and telencephalon. (See earlier diagram of the main parts of the non-mammalian brain.)

The diencephalon is the neural tube itself at that most rostral section. It is divided into two parts: the dorsal half, the thalamus, receives and passes on to the telencephalon all the forebrain's sensory input, and the ventral half, the hypothalamus, is the master control of the endocrine system (managing the messenger proteins, or hormones, in the blood) and the parasympathetic nervous system (sending nerves to internal organs). (The hypothalamus is, therefore, the main way in which the outputs of the animal behavior guidance system and the biological behavior guidance system are coordinated.)

The telencephalon develops from the same segment of the neural tube as the diencephalon. That segment of the neural plate does not close fully into a tube like the rest of the nervous system; instead, both sides are extended and thickened and become two, symmetrical flaps, which ultimately almost surround the diencephalon, as the telencephalon.

Forebrain output to the midbrain. The non-mammalian forebrain projects all its output to the midbrain, because that is where the optic tectum uses telesensory input to guide the locomotion in relation to the distant object (that is, where the animal representation of the object guides locomotion). The default behavior is normal locomotion and feeding. (Taste receptors have direct connections that affect feeding behavior.) Output from the forebrain modifies these behaviors and is responsible for selecting most other goals. The forebrain's outputs are all received by a region of the midbrain where the optic tectum influences the hindbrain motor commands and determines how the body moves in relation to the distant objects, approaching or avoiding them.

The most primitive output of the non-mammalian forebrain to the midbrain for choosing the goals of the behavior has already been mentioned. It originates from input to the olfactory bulb and reaches the midbrain by various ancient pathways, including some through the hypothalamus. This, together with another olfactory pathway (through the amygdala, a ventral part of the telencephalon), becomes the affective system in mammals.

It is the two other ways that non-mammalian forebrains can influence behavior that are relevant to the evolution of the subjective system of representation itself. Both of these other two outputs depend on visual, auditory or somatosensory input received by the thalamus and relayed to the telencephalon. But each involves a different target in the forebrain. One target is the (non-mammalian) dorsal cortex, the extended flap that develops from the neural tube at the diencephalon into the telencephalon, and the other is the striatum, a structure at the base of that extended flap. The dorsal cortex sends output to the midbrain by way of its connections to the extreme (medial) edge of the flap, which is (or becomes) the hippocampus. And the hippocampus projects, in turn, (by way of the fornix) to the hypothalamus, which sends output to the midbrain and to the mammillary body located in the hypothalamus. (The mammillary body has its own projection to the midbrain.) (See diagram of the hippocampal and striatal two pathway for forebrain output.)

The striatum, the other forebrain target, sends output to the midbrain by way of connections in and through the hypothalamus. (See diagram of the hippocampal and striatal two pathway for forebrain output.)

The size of the forebrain increases in vertebrate evolution, and the size and definition of the striatal and hippocampal pathways to the midbrain increase more than that of the primitive olfactory pathways. But the function of striatal and hippocampal output to the midbrain is basically to select the right kind of behavior for the distant object, including the construction of instinctive telesensory maps. They generate instinctive responses, including complex fixed action patterns, by modifying behavior that is already being adjusted to the currently detected distant object by the optic tectum in the midbrain.

For example, in an amphibian like the frog, visual input from the retina and optic tectum that is relayed (by the thalamus) to the striatum is used to select flight from large objects that are moving toward them (which are usually predators), suppressing their normal behavior of snapping at food. And visual input from the retina relayed (by the thalamus and dorsal cortex) to the hippocampus is used to keep frogs from jumping into walls. (See Macphail 1982 on amphibians and reptiles.)

In birds, at least, this hippocampal pathway evolved into a complete circuit for a one-dimensional, vision-based memory for retracing a pathway of salient landmarks, which approximates the mammalian memory circuit.

In the avian brain, the dorsal cortex contains a detailed visual image called the "visual Wulst" which controls locomotion by its own, direct motor output. It is part of a memory map that uses visual input relayed by the thalamus directly from the retina to the dorsal cortex. And as part of the dorsal cortex, the Wulst connects through the medial cortex/hippocampus and fornix back to the mammillary body in the hypothalamus. But instead of merely influencing the midbrain and motor output, as in other non-mammals, the mammillary body relays a signal, by way of the thalamus, back to the Wulst in the telencephalon. This is a complete circuit, resembling the mammalian memory mechanism, is apparently used to construct a memory map for guiding locomotion. Assuming it works the same way as in mammals, the Wulst can use a one-dimensional chain of stimulus-response connections as a map to guide locomotion without involving the rest of the circuit (hippocampus, fornix and mammillary body). But vision is the only sensory modality involved, and judging by the neurological mechanisms, it cannot use its memory map as a locomotor imagination.

Reptilian innovations. There is little change in the basic structure of the non-mammalian vertebrate brain (after the evolution of the jaw in fishes), except for three important changes, each involving one main parts of the brain, that came with the evolution of reptiles and the their use of legs to support the body.

Legs that could support the body made vertebrates better able to move across land, and new mechanisms were required to operate them. A new section of the cerebellum (the paleocerebellum) was required to balance the body on its legs and smooth out motor commands to them. And to serve this function, it has a somatotopic organization, that is, like a picture of the body.

The paleocerebellum projects to a new nucleus in the midbrain, the red nucleus, which uses a somatotopic array of neurons to send motor commands to the limbs.

Finally, the source of the more complex motor commands required to operate legs is a prominent, new structure in the telencephalon, the DVR (dorsal ventricular ridge). It is a major modification of the striatal pathway of forebrain output, because the DVR receives most of the thalamic relay of sensory input via this pathway to the telencephalon (including both the direct and the indirect visual channels), and the DVR projects to the striatum, by way of which its output reaches the midbrain and hindbrain areas for generating motor output. The DVR controls the motor commands from the red nucleus by way of a projection from the hindbrain to the paleocerebellum. (The main part of the DVR also projects to a more basal part of the DVR, which also receives olfactory input and projects to the hypothalamus, according to Ulinski, 1983.) (See diagram of the reptilian brain with paleocerebellum, red nucleus and DVR.)

To sum up, there are only three ways that the non-mammalian forebrain can affect the behavior being generated in relation to the distant object by the midbrain and hindbrain: the ancient olfactory pathway, the hippocampal pathway, and the striatal pathway. And the only input to the non-mammalian forebrain is the sensory input (indirectly from the midbrain and directly from the retina) registered in the thalamus of its diencephalon and relayed to various structures in the telencephalon — that is, except for the forebrain's own telesensory input, olfaction, and what the hypothalamus gathers from its control of the endocrine and parasympathetic nervous system. Although there is, as we have seen, a further development of the reptilian brain in birds, this is the basic structure of the reptilian forebrain from which the subjective animal system of representation evolves.

The gradual evolution of vertebrates. In the first section of this chapter, we found that the evolution of telesensory from somatosensory animals is inevitable because it is both possible and functional. In the second section, we saw how deuterostome development of chordates makes it easier to construct a nervous system with a telesensory level of part-whole complexity, and the third section described in detail the structures in the vertebrate brain that are the foundation for using the deuterostome capacity to determine entire 2-D arrays of neurons to construct a brain with yet higher level of part-whole complexity. We are following the inevitable stages of evolution that lead up to beings like us, and thus, it remains only to trace the gradual evolution of telesensory animals on earth. We may set aside animals with proterostome embryological development, because we have sufficient reason to believe that they are not capable of evolving beyond the telesensory stage. Let us consider briefly, therefore, the origin and evolutionary career of vertebrates, beginning with the somatosensory animals from which they evolved.

Somatosensory chordates. We are counting somatosensory animals as a necessary part of the multicellular biological stage of evolution, because we want to count how many distinct levels of part-whole complexity and, thus, how many distinct evolutionary stages, there are in the ladder that begins with the original proto-organisms and ascend to beings like us. The multicellular animals from which vertebrates evolved are somatosensory chordates, and they are represented by the brainless chordate, Amphioxus.

Without a brain, its nervous system is equivalent to the vertebrate's spinal chord. Relatively sophisticated swimming behavior is generated in its bilateral body by local connections between segments of its neural tube, each with sensory, motor and interneurons serving the three basic subfunctions of somatosensory animal behavior guidance systems. The function of selecting the right kind of behavior is served by a cough reflex at the mouth that rejects unwanted particles. And motor reflexes triggered by somatosensory input lead Amphioxus to burrow into sand at the edges oceans around the world in order to feed on microorganisms and protect itself.

Before vertebrates evolved, brainless chordates must have acquired free energy in more active ways than Amphioxus, feeding on microorganisms while swimming or seeking out multicellular plants to browse on. It is not known how vertebrates evolved from animals like Amphioxus, except that it was part of the evolution of telesensory organs. But it is no surprise that Amphioxus is the only extant representative of the first stage, because when chordates did evolve telesensory organs and a centralized nervous system to use them in guiding locomotion, somatosensory chordates were left with only the most low-energy, sedentary ecological niches.

Telesensory chordates (Vertebrates). According to the detailed fossil record, which begins with the Cambrian Period about 570 million years ago, vertebrates showed up about 500 million years ago, after almost every kind of marine invertebrate had already evolved.

Multicellular plants had evolved long before the Cambrian period, and what accounts for the fossils of animal skeleton that mark the beginning of that period is the evolution of the mechanism of embryological development (that is, the biological behavior guidance system for multicellular animals). The relatively late arrival of chordates suggests that deuterostome development evolved after proterostome development.

Vertebrates are named after the series of vertebra that enclose their neural tube, except at the head, where the brain is located. From the beginning, as we have seen, the vertebrate brain had three, anatomically distinct parts (midbrain, forebrain and hindbrain), serving, respectively, the three subfunctions of the animal behavior guidance system (input, choice and output), and we have seen how the function of the telesensory animal system of representation is served by its structure. There is remarkably little change in the structure of the non-mammalian brain, but the bodies of non-mammalian vertebrates underwent radical changes.

The most primitive vertebrates, jawless fishes (Agnathia), were still filter feeders. They actively scooped up detritus from the bottom, although their contemporary descendants, lampreys, have adapted the jawless mouth for preying on other fish.

From them evolved the now extinct, heavily armored placodermi, with a major reorganization of the hindbrain to operate its hinged jaw. The jaw not only made them ferocious predators, but also revolutionized the means of ingesting other organisms for all subsequent vertebrates.

Two kinds of fishes evolved from placodermi, cartilaginous (such as, sharks and rays) and bony. The cartilaginous skeleton was a departure from the bony frames of placodermi and jawless fishes. But bony fishes were so successful that there may now be as many as 40,000 species of them. The earliest of them were fresh water fishes, which had lungs as well as gills to supplement their supply of oxygen when the water was stagnant. In most extant species, the lungs have evolved into a swim bladder, which is also used for water-borne hearing. But one early lung fishes, the lobe-fin fishes (Crossopterygii), had fleshy bases for their two pairs of fins.

From lung fishes evolved amphibians. Their ability to pull themselves across the land opened up a new range of living objects to ingest, for by this time, plants and some insects had already invaded the land. (They were our first example of gradual evolution by reproductive causation, in Change: As aspect of substance: Global regularites: Reproductive: Gradual evolution).

There was room for improvement among vertebrates that completed cycles of reproduction on land. Although fertilization is still an external, water-based process in amphibians, it was done internally by reptiles. Reptiles not only had eggs with a shell that protected them from drying out as the embryos developed on land, but the reptilian body also acquired a dry, scaly, relatively impermeable skin. There were also advances in the heart and lungs. And whereas amphibians had short, weak limbs attached high on the sides of their bodies, reptiles evolved longer and stronger limbs that push directly downward, enabling their bodies to clear the land as they moved along. In order to operate these limbs, new structures evolved within the basic three-part structure of the vertebrate brain to send different motor commands to different legs (the paleocerebellum in the hindbrain, the red nucleus in the midbrain, and the DVR in the forebrain) . Reptiles also have air-born hearing, which among amphibians, occurs only in frogs.

Dinosaurs and birds evolved from reptiles. Dinosaurs were apparently able to move around very quickly on two legs, freeing their front legs to grasp other living objects; only as larger dinosaur species evolved did some return to four-footed locomotion. Dinosaurs may have evolved some control over bodily temperature, but we have little evidence apart from birds, which descend from an early dinosaur species. Hollow bones and feathers adapted birds to flight, and besides improvements in heart and lungs, they acquired the metabolism to maintain a high body temperature. Since hatchlings cannot acquire energy for themselves until their bodies have developed far enough to fly, birds also care for their young, a rather rare trait before the evolution of mammals. Birds also have, as we have mentioned, a one-dimensional, stimulus-response, vision-based memory for retracing a pathway, as in returning to a nest, patrolling a territory, or migrating with the seasons, and dinosaurs probably did too.

Although these changes in vertebrates required enormous periods of time, they are all at the same stage of animal evolution. Jawless fishes first appeared about 500 million years ago, about 70 million years after the start of the Cambrian period. The jaw evolved somewhat more than 400 million years ago, about the time that plants invaded the land. Amphibians evolved from the lobe-fined lung fish a little more than 350 million years ago, during the age of fishes. Reptiles evolved about 300 million years ago, late in the age of amphibians, and the dinosaurs evolved about 225 million years ago, after the decline of amphibians, followed shortly by birds (over 200 million years ago). The evolution from fishes to amphibians to reptiles to dinosaurs to birds is not a result of the dialectic of gradual and revolutionary change, because their nervous systems (and bodies) are on the same level of part-whole complexity. They are just a series of adaptations of an animal behavior guidance system with a telesensory animal system of representation (and the body it operates) to new habitats on land and in the air (though some used their improved design to return to water). These changes did not alter radically the structures of their brains.

6 Subjective stage. Subjective animals are multicellular animals with a higher level of neurological organization than telesensory animals. They are all mammals. We will see why mammals are inevitable and trace their gradual evolution. But as a result of explaining the mechanisms built into their higher level brains, we will also understand why there is a unity to the consciousness of mammals like us, finally repaying in full one of the four mortgages we took out to use spatiomaterialism as the ontological foundation for this argument.

The inevitability of an evolutionary stage following the evolution of telesensory animals depends, according to this ontological explanation of revolutionary change in evolution, on a higher level of neurological organization being both possible and functional. We have found good reason to doubt that such a higher level of neurological organization is possible in invertebrates. Their kind of embryological development is not able to try out the radical random variation required to organize neurons on a higher level of part-whole complexity. Or to put it positively, the main reason that such a radical random variation is possible in vertebrates is that their kind of embryological development is able to determine the fates of entire 2-D arrays of neurons as ordered units. That makes it relatively easy to organize such systems of neurons as parts of larger, complete circuits in the process of embryological development.

The mechanism of embryological development is, however, only part of the explanation of the possibility of mammals. Its possibility also depends on the way in which the more detailed structure of brains with the subjective level of neurological organization can be acquired from the structure of the world, that is, by learning from experience. Such learning is, as we shall see, a later phase in the process of neurological development in subjective animals, a stage during which detailed nervous structures evolve within the individual brain through natural selection by reinforcement (that is, as a form of evolution by reproductive causation that occurs within the mammalian brain).

If a further reason is needed for believing that the subjective level of neurological organization is possible, it will be found in following the actual evolution of nervous structures in the mammalian brain from the structures that were identified in the vertebrate brain in our discussion of the previous stage, stage 5. That is another way of proving that the structures to be identified in the mammalian brain actually have the functions that I will ascribe to them.

Both of these further reasons for believing in the possibility of the subjective level of neurological organization depend, however, on its function, that is, on how it opens up an entire, new range of powers that can evolve for controlling relevant conditions. Though I have already said that its function is to give animals spatial imagination, the time has come to explain what is meant by such a faculty of imagination and to describe functionally the systems and subsystems of the animal behavior guidance system that would give animals such a cognitive power. That is where we begin.

Function of the subjective level of neurological organization. Since animal behavior acts on other objects in space, its power can be increased, as we have seen, by adapting the behavior to spatial aspects of the situation in which the animal must act. That makes animals better able to control the conditions affecting their reproduction. One of those aspects is the way that the structure of the space, by helping to constitute what happens in the region, imposes regularities on how such objects can change location and interact with one another, or what I have called spatial causation (including how it helps cause local regularities ontologically as well as global). That aspect is, perhaps, better described as a spatio-temporal aspect of the situation, since it includes regularities about change. In any case, taking advantage of it in guiding their behavior to act on other objects in space is the basic function of spatial imagination. The function of the subjective neurological level is, in short, to understand spatial causation.

Spatial imagination. In order to show that such a faculty of spatial imagination would make animals inherently more powerful than telesensory animals, let us recall the cognitive powers of telesensory animals. Not only do telesensory animals have the capacity to guide behavior in relation to objects that can currently be perceived, but they also have the capacity to construct a map of the territory by which they can guide behavior in relation to objects that are not currently perceived.

The territorial map used by telesensory animals, such as bees and birds, is basically, however, just an elaboration of the complex instincts that have evolved in relation to the telesensory representations for detecting of kinds of objects in order to choose which of incompatible kinds of behavior to generate toward them.

The nervous mechanisms set up during embryological development is a structural cause not only for using input from the bodily condition to register telesensory input in a way that reveals the locations of perceivable objects in space, but also for the instinctive routines that use telesensory input to construct and use a map of its territory. The telesensory map is little more than a set of computational tricks that take advantage of the geometrical structure among salient objects on the surface of the earth to revisit energy sources and return to a nest or home base. Though computations on quantities like distance and azimuth and one-dimensional, stimulus-response chains for retracing pathways are effective, the isomorphism between states of the brain and the basic three dimensional structure of space is only implicit in them. Nor does it represent the effects of locomotion on the relations of objects in the territory, but merely guides actual locomotion.

These fixed action patterns built into the structure of the brain are called "programs of behavior" by J. Z. Young (1978, and 1981, p. 362), though Young assumes that they explain the behavior of mammals as well as that of other vertebrates and invertebrates.

The structure of space is, however, so important in determining the outcome of interacting with other objects in space that animals would be even more powerful, if the animal system of representation took greater advantage of it. Since material objects are substances that coincide with substantival space, they can change location, as we have seen, only by moving across space as time passes. And since space has a three dimensional structure, the effects of motion on the relations of objects in space is determined by the object’s speed and direction relative to them in space. This is a spatio-temporal aspect of the world, and adapting animal behavior to it would make animals more powerful.

Telesensory animals already adapt the spatial aspect of animal behavior to spatial aspects of the world. That is, they use their animal behavior over time to impose a kind of geometrical structure on the thermodynamic flow in a region that would otherwise require a giant machine. But instead of the unchanging geometrical structure of a huge material object, the structural cause is just an animal with a nervous system to guide its behavior so that it is in the right place at the right time to make things happen in the region that otherwise would not happen. Thus, it is an active, energy consuming way of imposing a geometrical structure that causes irreversible changes in the region that would not otherwise occur. This telesensory adaptation of the spatial aspect of animal behavior to spatial aspects of the situation is already to use a spatio-temporal aspect of behavior to control what happens to material objects located in the region.

Though animal behavior as such has a temporal aspect as well as a spatial aspect, telesensory animals do not adapt the spatio-temporal aspect of their behavior to the spatio-temporal aspect of the world. They adapt it only to the spatial aspect of the world. When they act on the perception of the object, it is the perception of the object in its current location. And if the other object is moving, that means guiding locomotion in relation to its current, albeit changing, position. However, when they act on their map of the territory, they assume that the locations of objects in their territory do not change. Their map gives them power over other objects by guiding locomotion in relation to unperceived objects whose locations do not change.

Animals would be more powerful, however, if they could adapt the spatio-temporal aspect of their behavior to the spatio-temporal aspects of the world.

If they could anticipate the consequences of the motion of objects on their relations to other objects in space, they could guide locomotion in relation not only to distant, unseen objects, but also in relation the future locations of objects that can move around in space. In chasing another animal, for example, they could move in the direction of its future location, rather than where it is currently perceived.

The capacity to anticipate the consequences of its own locomotion on the relations of their bodies to other objects in space would enable them, for example, to figure out an alternate route to its destination when the usual path is blocked, whereas the telesensory animal would be left with rigid routines that simply no longer work.

These examples emphasize the way in which anticipating the consequences of motion gives the animal foresight. But anticipating the consequences of motion is more generally useful, because, as we shall see, it is an understanding of the structure of space which makes the animal better able to take advantage of purely spatial aspects of the relations among objects in its territory than telesensory animals. In chasing another animal, for example, it could not only project its future location from its current motion, but also figure out where the animal might have gone in the territory when it can no longer be seen.

"Subjective" is an appropriate name for animals like this, because spatial imagination depends on internalizing the spatial structure of the world in a way that gives them an understanding of the structure of space. It depends, as we shall see, on a faculty of imagination in which sequences of memory images represent the consequences of locomotion relative to certain starting points. That makes it possible to think about spatial relations in terms of the consequences of locomotion (and motion generally), that is, as a spatio-temporal aspect of the world. That is to understand intuitively the role of space as an ontological cause of regularities about change, or “spatial causation.” (The use of sequences of image over time to represent what is possible means that this faculty might better be called “spatio-temporal imagination.” But it means that spatial imagination also includes the ability to record in memory and call up in imagination other spatio-temporal aspects of the world, such as regularities about change that do not have to do with motion, including how other animals behave).

Mammals have, therefore, a conception of space. They understand intuitively that space has three dimensions and what that means about the possible spatial relations among objects in space. They see other objects as being located in space. They even see their own bodies as having a location elsewhere in the same space as the other objects they perceive in space.

The subjective animal system of representation gives animals, therefore, the conception of the object as being located in space. But since location in space means having particular spatial relations to every other object in the world, spatial imagination is not merely a representation of the object as in space, but also a representation of the whole world, at least, in principle. And it is a world in which it can see its own body as just another object located in relation to every other object in the world.

This faculty of imagination enables animals to see the actual against the background of the possible, in this case, the actual locations of objects in space against the background of what is possible by motion. What space makes possible is presented as sequences of images along with perception (or the images derived from current sensory input), and thus, the possible has an appearance to the animal. The mammal’s animal representation of space is explicit.

None of this is even conceivable by the telesensory animal, because the location of the object is only implicit in its animal representation. When the telesensory animal focuses on the object, its location in space is not represented in the images caused by telesensory input. Its location is contained as a mere code for generating locomotion in relation to the object, should it choose to approach or avoid it, that is, as a disposition to move in certain ways. Thus, the telesensory animal is unaware that its own body is another object with a different location in space from the object being perceived. Indeed, it is not even aware that it has a body, except implicitly in special kinds of behavior, such as preening in birds, that has been selected for taking care of its own body. Otherwise its body is simply how it moves in relation to other objects and acts on them. It is as if the telesensory animal is its body, whereas the subjective animal is a subject to whom its body has an appearance, if only the appearance of being located in space relative to other objects.

Subjective animals require a higher level of part-whole complexity in the nervous system, because imagination depends on the capacity to generate behavior covertly and, by that covert behavior, to recall from memory the telesensory images that would result from those bodily movements. How the mammalian brain differs from the non-mammalian vertebrate brain is described below in detail, but first, the basic difference between the brain mechanisms of telesensory and subjective animals will be explained in functional terms.

Indeed, as an introduction to that functional description, the difference can be suggested by contrasting two kinds of computers.

Telesensory animals are comparable to the computer-guided robots found in factories and that have been used for exploring other planets. They can be programmed to generate routines in specific situations, but they rely on certain cues or landmarks to get around in space and, thus, can easily be confounded by changes in the locations of objects.

Subjective animals, by contrast, are comparable to computers that generate for beings like us what is called "virtual reality". In the computer memory are stored images of what would be seen if the human head were pointed in certain directions at each location for a whole set of locations to which a body can move, so that when sensors attached to a human body detect such bodily motion, they call up the appropriate image from the computer memory and project it onto a screen in front of the eyes, giving a human subject the appearance of moving around among the objects in some region of space. It generates an uncanny sense of being in an imaginary world, because the human being is playing the role of generator of "covert behavior" exploring a memory that is supplied by the computer, just as real covert behavior explores the memory of the subjective animal system of representation.

Functional diagram of subjective animal behavior guidance system. The various functions and subfunctions of the subjective animal system of representation are depicted in the accompanying diagram of the subjective animal behavior guidance system. Though neural mechanisms serving the function of selecting the kind of behavior are also essential to the animal behavior guidance system, only the mechanisms serving the sensory input and behavioral output subfunctions are involved in the animal system of representation (all the parts with the gray background). The higher level of neurological organization is suggested by the contrast with the diagrams of the somatosensory and telesensory animal behavior guidance systems (which are also provided for comparison.)

In the subjective system, the sensory input and behavioral output systems both depend on an interaction of at least three brain mechanisms, each at the same level of neurological organization as the whole sensory input or behavioral output system of telesensory animals. Indeed, as the diagram suggests, each is a complete circuit of such mechanisms.

The brown squares and lines are basically the systems and causal connections serving the functions that are also served by the telesensory animal system of representation (including telesensory input, input about the current bodily condition, their combination as the perception of the object, and how that is responsible for overt behavior when some kind of behavior is selected). The higher level of part-whole complexity in the subjective sensory input and behavioral output systems makes it possible for them interact in the more complex way that constitutes imagination.

The red circles and lines (in each brown square) represent the systems and causal connections serving new functions required by spatial imagination (including the body image, covert locomotion, memory, the local image, the sequences of images, or spatio-temporal images, called up from memory by convert locomotion, and the behavior generator). Here is how it works as a faculty of spatial imagination.

(The three systems in each complete circuit include a thalamic nucleus, at least one region of neocortex, and a third structure of some kind, which is suggested by the two circles and a little ball. The neural mechanisms serving these functionally described systems are identified in the next section, on the structure of the mammalian brain.)

Local image. The telesensory input registered by the sensory input system includes all the telesensory modalities. Vision and hearing are most central, though olfaction is still used. Input about the current bodily condition has the same function with respect to telesensory input as it does in telesensory animals, except that by handling all the telesensory modalities together, it can construct a more complete representation of the current scene, or what is labeled as the “local image.”

Though the local image represents only objects that can be perceived from the animal’s current location, it also represents some objects that are not currently causing telesensory input. Telesensory input from objects located behind the animal at the moment, for example, is registered in short-term memory according to the bodily condition at the time it was perceived, while the objects on which the eyes focus or that are making noise are currently causing telesensory input. But since these telesensory images are all part of the local image, objects are perceived as being located relative to one another in the current scene, and behavioral output can be adjusted to them all (when some kind of behavior is selected).

Though the local image is a complex of many telesensory images which can guide behavior in relation to many different objects, it is the unit that becomes connected in sequences as the subjective animal’s territorial map in spatial imagination.

Body image. Overt behavior is caused by motor output to muscles throughout the body. The behavioral output system is labeled the “body image” because commands for overt behavior are sent from a representation of the body. The body image is a spatial structure in various 2-D arrays of neurons that represents somatotopically all the parts of the body whose behavior it controls, and it receives somatosensory input from all the same parts of the body, indicating the positions and motion of limbs, the stress of muscles, tactile sensations from the skin, and pain from injuries.

Tactile sensations reveal information about objects that contact the body, and since the stance of the body is represented, it reveals information about the location of the other object causing the somatosensory input. (Such information is registered as part of the local image by way of its input about the current bodily condition, though there are reflexes that can trigger behavior locally without involving the selection system, for example, in response to intense heat or pain.)

Behavior generator. Most motor commands in the body image are generated, however, by another part of the behavioral output system, labeled the “behavior generator.” The behavior generator contains schemata for all the various kinds of behavior that may be selected, and depending on its input from the goal selection system, the behavior generator uses one of them together with the perception of the object as located in space (that is, the local image, its input from the sensory input system) to generate precise motor commands that are adapted to the locations of relevant objects in the current scene. Thus, behavior may be guided in relation to perceivable objects even though they are not currently causing any telesensory input.

Moreover, the behavioral schemata used by the behavior generator may involve many steps, because the behavior generator has feedback from the motor commands issued by the body image by which each motor command triggers the next in a sequence, generating temporally complex patterns of behavior. There is a wide range of variations on behavior that may be included in such behavioral schemata, since motor output sends commands separately to each part of the body.

Thus far, the subjective animal system of representation serves basically the same functions as the telesensory animal with respect to currently perceivable objects, though in a more complete way, since its higher level of neurological organization integrates all the kinds of telesensory (and somatosensory) input as a local image on the input side and can generate a great variety of long sequences of complex motor commands on the output side. What is new is spatial imagination. Though spatial imagination serves the same function as the telesensory map of the territory animal, it is so much more complete that it represents an aspect of the world that inevitably escapes telesensory animals: regularities about how motion and locomotion affect the relations of objects in space. That is the source of the subjective animal’s conception of space.

Memory. The new subsystem in the subjective animal’s sensory input system is a special kind of “memory” which is able to record images in sequences so that they can be called up in the same sequence. The images may be just telesensory images of an object, for example, recording what happens as another animal behaves. But they can be entire local images. That is, various telesensory images representing a local scene (with each registered according to the bodily condition relevant to receiving it) can be recorded together as a memory unit, and local images can then be recorded in sequence according to the direction of its locomotion. The effects of locomotion in different directions from any given scene are recorded in different sequences.

Overt locomotor behavior is registered, not only in the local image by way of input about the current bodily condition, but also directly in the memory system by way of the “covert locomotion” connection. The direct connection to memory is what is used to label local images in constructing the map.

Covert locomotion. What calls up the local images recorded in this way is a new capacity of the subjective behavioral output system, the capacity to generate behavior covertly as well as overtly. In covert locomotion, the same motor commands that would otherwise cause locomotion in a certain direction relative to a local image are generated, but in a way that does not affect the body. It affects only the memory based in the sensory input system. Since local images have been recorded as units labeled by the appropriate bodily condition (mainly the stance of the body, head, eyes, ears and the like), and since local images have been connected in sequences according to the bodily condition at the time (mainly the direction of locomotion relative to the local scene), covert locomotion calls up the sequence of local images that would be encountered if the animal actually moved in that direction. The local images called up from memory are projected in a sequence over time to the behavior generator in the same way as images of perception, though they are just memory images (labeled “spatio-temporal images” in the diagram) and can occur faster. Thus, the behavior generator can use the local images from memory to generate covert locomotion in relation to unperceived objects in the same way as perceived objects, drawing on its schemata for various kinds of locomotion and generating motor commands in relation to objects in the imagined local scene (represented by the local image).

Together, such sequences of local images serve as a map of the animal’s territory. For example, if a local image that turns up in exploring one sequence by covert locomotion is registered as (or simply recognized as) part of another sequence of local images representing locomotion in another direction, the subjective animal can change the direction of its covert locomotion relative to that local image and anticipate what would happen from turning at that location in the other direction. In familiar territory, such sequences of local images are richly interconnected, but in any case, they give the subjective animal a map of the relations of objects in its territory. The subjective map is different from the telesensory map, because it can guide covert as well as overt locomotion in relation to goals picked out by the selection system. Thus, far from being merely a conditioned stimulus-response chain that leads the telesensory animal from one location to another as parts of a instinctive routine for controlling a specific relevant condition, memory is a potentially complete, general purpose map of all the objects in its territory which can be explored in imagination by covert behavior.

Evolution of behavioral schemata within the brain. Locomotion, covert or overt, is generated by behavioral schemata, and not only do subjective animals have many different ways of moving and turning in relation to other objects in space, but they also have other kinds of behavior. Though schemata for basic forms of behavior may be built into the structure of the brain (indeed, must be in the case of mammals that have to be capable of locomotion from birth), they can also be learned. And in any case, the consequences of acting on them is learned, and thus, how to adapt them to the situation is learned. Learning transforms the subjective animal’s map of its territory into an understanding of the structure of space, and we can see why, by recognizing that learning is a from of evolution by reproductive causation. Subjective animals learn as behavioral schemata evolve in the brain as the result of a form of natural selection that I will call “reinforcement selection.” Learning is a later phase of neurological development that occurs when the animal is interacting with the world, and its effect is to internalize certain aspects of the world in the skills and imagination of the subjective animal. Let me describe how learning can be seen as a contained form of evolution by reproductive causation, setting aside until later discussion of the neural mechanisms that serve these functions.

The “reproducing organisms” in this case are the behavioral schemata used by the behavior generator to generate motor commands in the body image. They go through reproductive cycles in the sense that, once they have generated behavior, they can do so again.

Variations on behavioral schemata are possible, because behavior is generated by motor commands to all parts of the body from the body image. Not only can highly varied (and finely tuned) kinds of behavior be generated, but such complex motor commands can also be generated in different sequences over time as parts of a single action. By rearranging the motor commands, variations on behavioral schemata can be generated more or less randomly.

The natural selection of behavioral schemata is made by their being recorded in memory. Such recordings increase the likelihood that the same kind of behavior will be generated again. (Basically, the synapses among the neurons used to generate the behavior are strengthened.) The behavioral schema reproduces when it is used again to generate behavior.

Since behavioral schemata are used to generate behavior in conjunction with the perception of the object acted on, they are recorded together with telesensory images of those objects in the local image. Two kinds of connections are established between telesensory images and behavioral schemata. Telesensory images of objects (or their local images) that precede the behavior may help trigger the behavioral schemata, when they recur in perception. And when behavioral schemata are used to generate covert behavior, they call up telesensory images (or local images) of what results. These connections are the way local images are recorded in sequences, so that they can be called up as spatial imagination, by locomotion and turning.

The criterion for natural selection (that is, recording it in memory) is basically whether the behavior generated by the schemata satisfies a relevant desire. The recording is made by the memory circuit, and its criterion comes from its relationship to the goal selection system. Random variations that do not succeed in satisfying desire are not recorded.

In learning basic kinds of behavior, the relevant desire is mainly just that its expectations about telesensory images be confirmed by what shows up in perception. The ecological niches are basic behaviors required to perceive objects in different directions and to move from one local scene to another, and the behavioral schemata that are adapted to those ecological niches internalize some basic aspect of the world.

This contained form of reproductive causation is the mechanism, in mammals, that behaviorists, like B. F. Skinner, called “operant conditioning.” What they called “operant behavior” is behavior generated by behavioral schemata. What they called “reinforcement” is natural selection by recording the behavioral schemata in memory. What they called “discriminative stimuli” are the telesensory images (or entire local images) that help trigger the behavior again.

Explaining operant conditioning in terms of the subsystems of the subjective animal behavior guidance system enables us to see this important kind of learning as a form of gradual evolution. Behavioral schemata start off simple, uniform and weak, and as a result of “reinforcement selection,” they become complex, diverse and powerful in generating behavior that can satisfy desire. The gradual evolution of behavioral schemata is the increasing power of the animal to control relevant conditions.

Though it is contained within the individual brain, it is a form of reproductive causation. Not only is natural selection made by success in reproduction, but reproduction is also what forces a selection to be made. The ecological niches in which behavior schemata can complete their reproductive cycles are situations in which the animal must behave in some way, and the reproduction of one behavioral schema (by its reinforcement) in such an ecological niche tends to cause a “scarcity” of opportunities for other behavioral schemata to be generated, because the animal can behave in only one way at a time as situations of that kind arise. To be reinforced, a behavior schema must generate its behavior at some time before its memory group fades away from disuse, and thus, the scarcity is caused by how reproductive cycles add up in time (rather than by how reproductive cycles add up in space as time passes, as in biological evolution). But as random variations on behavioral schemata are tried out in such an ecological niche, those that satisfy the desire most efficiently are reinforced, and thus, “reinforcement selection” causes a stage of gradual evolution in which each behavioral schema becomes maximally efficient at satisfying some desire in certain situations (its ecological niche), and the combination of behavioral schemata at the ecological level, or the animal’s repertoire of behavior, comes to satisfy all its desires in all the situations it encounters as fully as possible with the least effort required. At both the individual and ecological levels, therefore, behavioral schemata change in the direction of natural perfection, that is, doing the most with the least.

What the doctrine of operant conditioning leaves out, however, is the faculty imagination. Though operant conditioning may be adequate to explain learning in telesensory animals, it leaves out important aspects of learning in subjective animals that depend on spatial imagination.

The relevant consequences of behavior are not limited to whether the behavior is reinforced or not. When a behavioral schema is reinforced, what happens, that is, the telesensory images (or local images) of what happens, are also recorded in conjunction with the behavioral schemata. Thus, when a behavioral schema is generated covertly, those images are called up in memory. Thus, when the subjective animal moves or turns covertly in the local scene, it can anticipate the objects and other local scenes it will encounter. This is a map of the animal’s territory, because when covert locomotion or turning is made relative to a local image, it calls up other local images relative to it. Thus, the subjective animal can explore its territory in imagination.

But the capacity to record and recall local images according to locomotion is not just a map of a particular territory. Learning to construct and use memory maps gives the subjective animal a general conception of space by which it can understand any relations in space by imagining the kinds of motion that would be involved in traversing or changing them. This general understanding comes from how the memory system reinforces behavioral schemata. The same kinds of locomotion have the same kinds of effects in similar local scenes. For example, when confronted with a large object, moving around it to the right and then turning left will give one a different view of the object. Or when one encounters a hill, climbing it will give one a view of what is on the other side. Two right turns in succession sends one in the opposite direction. Thus, by recording local images with similar structures together as the same generalized local image, covert locomotion becomes a general understanding of the structure of space, because the subjective animal has a “map” of the consequences of locomotion that would work for all local scenes of that kind. And by generating a sequence of locomotor schemata in sequence, it could anticipate the general consequences of combining them in certain ways.

In other words, the spatial structure of the world is internalized in spatial imagination because of how the memory system records behavioral schemata. It is the spatial structure of the world that accounts for the regular connection between kinds of locomotion or turning and the kinds of changes that occur in local images, and a behavioral schemata evolves by reinforcement selection, the connections in the memory system internalize those general relations. Their internalization is the subjective animal’s conception of space.

Understanding the structure of space. Though spatial imagination is based on a map of the territory in which the consequences of locomotion are represented by sequences of local images, the way that behavioral schemata evolve within the brain by reinforcement selection means that it is also a more general understanding of the structure of space. That is, it internalizes not only the particular relations among material objects in the animal’s territory, but it also internalizes the structure of space itself. In both cases, it is spatial imagination, because the understanding comes from the sequences of local images that can be called up covert locomotion (and turning).

What would happen because of locomotion (or the motion of any object) relative to objects in a local scene can be anticipated, because spatial imagination, that is, the capacity to generate behavior covertly, calls up from memory sequences of local images that represent the consequences of such behavior. The local images can be particular or general. Covert behavior acts on memory in similar ways in both cases. The difference is whether covert behavior engages with the detailed, particular local images that are the map of its territory or it operates on more generalized local images, which contain only certain relevant features. (They are actually groups of more specific memory images. We shall see how such general memories are possible when we take up the nervous mechanisms that serve these functions.)

Since spatial imagination gives the subjective animal an understanding of the effects of locomotion and turning in any space, it can see the objects in any local scene as being located in space. That is, the way that general local images are called up in sequences up by covert locomotion represents general regularities that are caused ontologically by the structure of space, and since those regularities hold not only among local scenes, but also among the objects within any local scene, the subjective animal has an intuitive understanding of the constraint that space imposes on change. That is the sense in which it perceives the object as being located in space. It is a conception of the structure of space.

Since spatial imagination gives the subjective animal a conception of space, the subjective animal sees not only other objects, but also its own body, as located in space. The local image is organized relative to the body, since telesensory images are combined as parts of it according to input about the current condition of the body. But since the subjective animal eventually acquires an understanding of the structure of space, that understanding applies to objects within the local image, and that includes the ability to think about the body as another object in space. The subjective animal can imagine not only its own body moving relative to other objects in the local scene, but also the effects of other objects moving in relation to its own body — as well as relative other objects in the local scene. Thus, even the body itself is represented as an object in the local image.

To sum up, we might even say that the subjective animal is able to see the world as a whole. To be sure, its map of the relations of objects in space is limited to objects in its territory. But it has a way of understanding spatial relations that can be extended, in principle, to include every object in the world. Thus, given how the world has a wholeness that comes from the structure of space, the mammal sees the world as a whole. Since such subjective animals have an intuitive (nonlinguistic) understanding of how a world of objects in space is inherently whole, they can perceive objects as part of a single whole.

Behavioral evidence of spatial imagination. As suggested at the outset, spatial imagination makes subjective animals more powerful than telesensory animals in various ways.

Spatial imagination give the subjective animal a map that not only guides instinctive behavior in relation to objects in its territory, but also enables the animal to see particular objects as having particular locations relative to others. It is a set of beliefs about the whole world that is based on being able to understand the consequences of motion relative to them. And since it is a general purpose map of the animal’s territory, rather than just an elaboration of instinctive routines for acquiring energy, mating, avoiding predators or the like, it can be used in pursuit of goals that were not relevant to its being acquired.

It enables subjective animals to plan new routes to goals when their paths are blocked, to figure out how to escape predators, to predict which direction prey might run, to choose the best way to catch them, and the like. It is the "inner world" to which Dennett (1975) was pointing in his famous essay, "Why the Law of Effect Will Not Go Away", when he said (paraphrasing Popper) that animals have an inner world that allows "hypotheses to die in their stead".

It gives subjective animals a primitive way of reasoning, for they can draw inferences about a world of objects in space. The animal system of representation is based on the assumption that objects do not come into existence or go out of existence, and with spatial imagination, that assumption can, for example, be used to infer where an object that it is seeking is located by knowing where it is not located and has not been. As a form of understanding, therefore, spatial imagination is a way of using current beliefs to form new beliefs, that is, a way of making inferences.

There is empirical evidence that spatial imagination makes mammals more powerful than non-mammalian vertebrates.

But it should be noted that not everyone agrees that mammals are more intelligent than non-mammals. In a study by Macphail (1982), the behavioral criteria used to argue that mammals are not measurably more intelligent than non-mammalian vertebrates do not take into account the capacity to get around in space. And although Gallistel (1990) recognizes that memory files are labeled spatially, he does not recognize the difference between the instinctive computational routines used by telesensory animals and a subjective memory based on the three dimensional structure of space. In general, there is no recognition in the literature of mammalian superiority.

Experiments demonstrating that rats use a representation of the spatial relations of objects in the local scene to orient their locomotion are reviewed by Gallistel (1990, Ch. 6). And rats that were not merely conditioned to the unusual environments that Gallistel discusses, but raised in them, should make even better use of the cues about spatial relations of objects in the region, because they would have internalized a map using input about the kinds of bodily conditions required. In any case, it is easy for mammals to learn mazes, because the mechanisms of spatial imagination acquired from experience with a world of objects in space would enable them to construct a new map for the maze.

There is evidence of inferences based on spatial imagination in how mammals in familiar mazes take advantage of apparent new shortcuts to the goal in otherwise familiar mazes. For example, if, at some point in a maze that a rat has learned, the normal route is blocked and barriers are removed both in the direction of the goal and in the opposite direction, the rat will take the new route to the goal, not the other one. (See Charles Taylor, 1964, pp. 161.196. These experiments pose a problem for traditional learning theory, which explains maze behavior as chains of discriminative responses. See also Gallistel 1990, Ch. 5.)

Even birds do not take advantage of shortcuts (when walking) through mazes, despite being able to learn mazes almost as quickly as mammals. In fact, once birds have learned a maze, it is surprisingly difficult for them to learn changes in it at all. Although birds have a mammal-like memory circuit, this suggests that, at least, when it comes to walking, it is not a spatial imagination that gives them an understanding of the structure of three dimensional space.

Subjective animal behavior guidance system. The faculty of spatial imagination serves as the animal system of representation in subjective animals, and in order to be of use in guiding behavior, the right kind of behavior for each situation must also be selected. Indeed, selecting between incompatible kinds of behavior is the original function of the animal behavior guidance system. And imagination also makes subjective animals better able to tell which goal to pursue in the situation.

The goal selection system. The kind of behavior generated must be made to depend on the situation, either the kinds of objects that are present in the local scene or the current needs of the body (or both). In subjective animals, goal selection is not just a matter of instinctive routines, but depends on desires, which are dispositions to behave in certain ways. Thus, its goal selection system might also be called the “affective system.”

The seat of desire is the goal selection system, for it registers of the various needs of the body and keeps track of the success of behavior in satisfying each of its desires.

Special input from the body is supplied to the goal selection system by the biological behavior guidance system (not represented in the functional diagram).That keeps the goal selection system informed of the body's need for food, water, sleep, mating and the like.

Objects represented in the sensory input system also have affective labels, which can arouse desires in the goal selection system or determine which object to pursue when a desire is already aroused. Some affective labels are instinctive, that is, built into the structure of the animal behavior guidance system, such those for avoiding certain predators and mating. Other affective labels are attached to objects by the goal selection system according to past experience. That is, the goal selection system can use the results of behavior to label objects by their capacity to satisfy desire, so that objects can be recognized for their capacity to satisfy desire when they are encountered again.

In either case, when the object turns up in the sensory input system, the desire may be triggered. But if the desire is aroused by bodily needs, telesensory images of the relevant objects may be called up from memory by their labels.

Whether the desire is aroused by sensory input or bodily needs, the goal direction system selects the appropriate kind of behavior by strengthening a certain behavioral schema in the behavior generator. (This is represented in the functional diagram by the projection from the goal selection system to the behavioral output system.) In other words, in terms of behavior, desires are dispositions to behave in some way, such as eating, mating, fighting, fleeing, and sleeping. But since animal behavior acts on objects in space, the desires that have this effect on the behavior generator must also be attached to an object.

When the object represented by sensory input is what arouses the desire, the object for the behavior schema to act on is already determined. If there is an obstacle in its way, it poses a problem that the subjective animal may be able to solve by spatial imagination. For example, it may use covert locomotion in its map of the territory to figure out a route that would put its body in the right location to act on the object as it is disposed to.

If the desire is aroused by bodily needs, the behavioral schemata it calls up may include searching for objects that will satisfy it, as in foraging for food and finding shelter. Or it may call up images of objects that will satisfy it, and if such images happen to be part of some local image in the map of its territory, the mammal can explore its map covertly to set up the locomotion that will lead to it.

In either case, instead of the telesensory animal’s rigid instinctive routines, desires set practical problems to be solved by using spatial imagination to imagine alternatives, and so subjective animals would be able to behave in a more flexible and adaptive way when necessary.

The goal selection system is the third essential subsystem of the animal behavior guidance system (along with the sensory input and behavioral output systems), and though it is not depicted in the functional diagram, it is also on the subjective level of neurological organization, like the other systems. There is a seat of desire, and it interacts through a complete circuit of connections with the other two subsystems. That is how it is able to attach the desires, or dispositions, to the right objects.

Sleep and dreaming. Dreaming, or REM (rapid eye movement) sleep, evolves with mammals (although there is some evidence of it in birds), but it has long been puzzling what its function could be. Given the evolution of spatial imagination in subjective animals, however, its function could be to try out random variations on behavioral schemata so that reinforcement selection can be more selective in attaching the right desires to the right objects in the right situations.

The attachment of desires to objects is a crucial function in behavior guidance, because it sets the goals for animal behavior. The animal will not be as powerful as possible, for example, if it fails to attach the desire to eat to objects from which it can acquire food, and it can be disastrous to attach the desire to eat to a predator. Furthermore, the task becomes increasingly complicated as the behavioral schemata for satisfying certain goals become increasingly complex. In the behavior schemata for attaining certain goals, behavior towards several objects of various kinds may be involved. Special routes through the territory may be needed to acquire food in certain ways. Some locations or objects may be dangerous. And social relations require different attitudes toward different members of the group not only in the family but also when there is a dominance hierarchy.

Reinforcement from satisfying desire is responsible both for attaching desires to objects and for strengthening behavioral schemata for satisfying them. Indeed, they are the same thing, because behavioral schemata that are naturally selected by success in satisfying certain desires include images of the objects and situations in relation to which the behavior generator sets up the motor commands. But natural selection by reinforcement is not very selective when success comes from subtle variations on complex behavioral schemata or accidents. Established behavioral schemata may be more powerful with their parts rearranged. Thus, reinforcement selection would be more effective in making behavior maximally powerful, if it had a wider range of random variations from which to choose, as long as it did not risking making disastrous mistakes.

Spatial imagination makes it possible for subjective animals to try out random variations on behavioral schemata in a safe way. Indeed, the regular use of spatial imagination in that way may be the function of dreaming.

Behavioral schemata are connected with both the desires and situations in which they are acted on, but they are often complex behavioral schemata, and thus, if the subjective animal could shuffle the elemental schemata making up its habitual repertoire and try out new combinations, testing them by the consequences associated with each in past experience, it could discover new complex behavioral schemata that are likely to work better.

If the trials were informed by memory of past successes and dangers, the random variation would come with certain emotions attached, including warning of possible dangers in acting on them as well as the attraction of potential benefits.

Dreaming requires long periods when the animal was not otherwise occupied, and that would be provided by regular periods of sleep. Indeed, if dreaming is functional in this way, it may be the function that explains sleep in mammals.

For further evidence of this function of dreaming, see Jonathan Winson's Brain and Psyche: The Biology of the Unconscious.

Acting. The selection of the kind of behavior toward an object is, however, a multi-step process. First, the goal selection system attaches a desire to the object. The animal system of representation must then figure out how to adapt a relevant behavior schema to the world. Finally, something must trigger the command to convert covert motor commands into overt motor commands. That is, it must act on its plan. The systems responsible for the first two steps have been explained, but the decision to act on its plan requires an additional mechanism. When we take up the structure of the mammalian brain, therefore, we will also be looking for a mechanism that makes acting overtly depend on a state of the animal behavior guidance system as a whole.

The possibility of a subjective level of neurological organization. The functional representation of the subjective animal system of representation makes it clear that any animals that happened to try out such a behavior guidance system would be able to acquire an entire range of new powers for controlling relevant conditions in a long period of gradual evolution. They would, in other words, begin a new stage of animal evolution, refining the inherent powers of spatial imagination and adapting it to all available ecological niches. But in order to conclude that such an evolutionary stage is inevitable, it must be possible for a radical random variation to try it out. There are good reasons to believe that it is possible, but in the end, the most compelling case depends on seeing how these functions are served by nervous mechanisms.

It may seem that any neural mechanism complex enough to realize this functional description of the subjective animal system of representation would be too complex to be tried out as a radical random variation on the telesensory system by the multicellular biological behavior guidance system. The functional diagram indicates that it requires a higher level of neurological organization than telesensory animals. But since the mechanism of embryological development must get all its instructions from the structure of the nucleus and the chromosomes it contains, such a higher level may seem beyond the range of random variations being tried out, especially considering that more complex neural connections are needed for higher level systems to interact as an animal behavior guidance system.

This is the same kind of problem that we faced in explaining the eukaryotic and multicellular levels of biological organization. But there it required a new kind of biological behavior guidance system, and here a different kind of solution is required, for the same biological behavior guidance system is responsible for all the levels of neurological organization. The appropriate random variation must somehow occur in the multicellular biological behavior guidance system (the process of embryological development).

There are at least three reasons for believing that such a random variation is possible.

First, one reason was found in how deuterostome embryological development is different from proterostome development. With the neural tube divided into segments, the mechanism of embryological development can address entire 2-D arrays of neurons and determine them, as a whole, to migrate or send processes to other areas of the neural tube (or the body), and to make topologically ordered connections with 2-D arrays of neurons there. That means, as suggested earlier, that the units from which deuterostome development constructs the nervous system are already on a higher level of organization than in proterostome development — not to mention that the connections among such units can be made without interference with the development of other organs in the body, since the neural tube itself is separate from the rest of the body.

Second, it is not necessary for the mechanism of embryological development to prescribe all the neural connections involved in the subjective animal system of representation, because the three basic systems are laid out in such a way that most of the detailed connections they require can be acquired from the world by learning. Since the power of animal behavior comes from adapting it to spatial and spatio-temporal aspects of the world, it is possible to internalize the detailed structural causes of the brain mechanisms that serve that function from experience with the world. The world already has a spatial structure, and if the animal is protected and cared for during the first part of its life, its interactions with the world can internalize the structures needed to construct local images and maps of local images that can be explored by covert locomotion. Thus, much detailed structure can be supplied by the contained form of reproductive causation mentioned above, in which behavioral schemata evolve by reinforcement selection. This is the role of nurture as well as nature in neurological development.

Third, given how detailed neural connections can be internalized from the structure of the world by experience, that is, learning, all that is necessary is a random variation that would set up the basic structure on a higher level of neurological organization within which those detailed structures can be acquired. As it happens, there are two, connected kinds of changes in the embryological development of the non-mammalian vertebrate that do set up a higher level of neurological organization in the mammalian forebrain.

In order to give this final argument for the possibility of the subjective level of neurological organization, therefore, we must consider the structure of the mammalian brain.

Starting with the functional diagram of the subjective animal behavior guidance system, I will, first, simply identify the neural mechanisms in the mammalian brain that are responsible for each of the subsystems. This is to view the structure of the mammalian brain from a rather high altitude. It affords a general impression of how the mammalian brain works, and for those who are familiar with its structure, it will be possible to see how it explains the functioning of the mammalian brain.

Second, I will explain how this functional explanation of the structure of the mammalian brain would also explain the contained form of reproductive causation by which behavioral schemata evolve in the individual brain by reinforcement selection.

Finally, in order to show how the subjective level of neurological organization is possible, I will show how it could arise from two basic, yet simple changes in the non-mammalian vertebrate brain. That will involve a much more detailed description of how the functionally identified systems are realized in the mammalian brain.

Neural structure of the subsystems of the subjective animal behavior guidance system. In the diagram of the subjective animal behavior guidance system, the systems that were previously defined functionally are labeled by parts of the nervous mechanism that serve their functions in the mammalian brain. (The functional diagram is included for comparison.) The brain mechanisms involving the neocortex are depicted as beveled buttons, while the thalamic nuclei projecting to them are depicted as purple spheres. Notice that when we look more closely at the detailed structure, the behavior generator itself is a complete circuit of telesensory-level nervous mechanisms. That is because there are two, distinct circuits within the behavioral output system, one that supplies the behavioral schemata and generates covert behavior and the other that also generates overt behavior. (Covert behavior needs only the ventral anterior thalamic nucleus, whereas both it and the ventral lateral thalamic nucleus are involved in generating overt behavior.) The part of the frontal neocortex that contains the behavior schemata and where covert behavior is generate is labeled “Sch.”)

This key to the neurological interpretation of the functional diagram of the subjective animal behavior guidance system may be enough for those who are familiar with the structure of the mammalian brain to see the functional diagram as an explanation of how the mammalian brain works. But for those who are not familiar with the structure of the mammalian brain and want a briefer, more intuitive way of seeing how it realizes these functionally defined systems, the following diagrams and brief explanations may suffice.

In the mammal, the entire animal behavior guidance system is located in the forebrain, and its basic structure is composed of two main units, the thalamus and the neocortex. The thalamus is at the end of a brain stem, just rostral to the midbrain, hindbrain and spinal chord, and it sends a massive projection to all parts the neocortex, which encloses the rest of the forebrain. (A projection is a set the axons from a 2-D array of neurons in one region to a 2-D array of neurons in another region, taking full advantage of the chordate’s way of constructing the nervous system in the neural tube.) The nuclei in the thalamus send their projections mostly to different parts of the brain (though the anterior temporal cortex receives none). There are also projections back from the neocortex to thalamic nuclei by which they interact in some way, but the main direction of influence is from the thalamus to the neocortex. These thalamic projections are 2-D arrays of neurons in which the information conveyed by the firing of any single neuron depends on the neuron's position in the 2-D array as a whole, and the thalamus apparently has the function of synchronizing the processing in all the parts of the neocortex.

There are three grand, distinct circuits of connections, each involving many such 2-D arrays, that pass though the thalamus and the neocortex back. That is, each circuit uses some part of the projection of many 2-D arrays from the thalamus to the neocortex, but each has a special way by which the neocortex completes the circuit of multiple 2-D projections by acting on those same thalamic nuclei (that is, distinct from the connections by which the neocortex reacts to the thalamus directly). Each such circuit is one of the three main subsystems of the animal behavior guidance system, with the circuits themselves on the subjective level of neurological organization. (See diagram of the basic structure of the mammalian brain.)

In the framework of this basic diagram, we can see how each of the functionally defined subsystems is realized by the mammalian brain. Consider first the sensory input system. Visual input from the eyes is relayed by the lateral geniculate nucleus (labeled "LGN") to the occipital (or striate) cortex where there are numerous copies of the entire image from the retina of the eye. Auditory input is not represented in the diagram, though it is handled in the same way, with auditory images in the superior temporal lobe. The inferior parietal neocortex is where the telesensory images are assembled as the local image (using association fibers from the motor areas, or body image, to supply information about the current bodily condition, also not depicted). The activity of the inferior parietal area in constructing the local image also depends on its interactions with a thalamic nucleus called the "pulvinar" or (labeled "Pul.," which receives input from the superior colliculus in the midbrain, the main visual image in the non-mammalian vertebrate brain).

The memory is what gives the sensory input system a complete circuit from the thalamus through the neocortex back to the thalamus for another projection to the neocortex. The memory circuit receives information about the telesensory images and how they have been combined as the local image in the anterior temporal neocortex where the hippocampus is located. In fact, almost every region of neocortex sends association fibers (or chains of association fibers) toward the anterior temporal neocortex, where they are assembled for the hippocampus (in an adjacent region, called the “entorhinal cortex”). The hippocampus projects by way of the fornix to the anterior nucleus of the thalamus, though many of its fibers pass first to the mammillary body (located in the hypothalamus) which relays them to the anterior nucleus. The anterior nucleus projects to the entire cingulate gyrus, which is the extreme medial edge of neocortex adjacent to both anterior and posterior regions of neocortex. The cingulate neocortex has two way connections with neurons in adjacent areas of neocortex. That completes the memory circuit for the local image and its bundle of telesensory images, since those images are affected by their own projection through the memory circuit. And the function of this circuit is to form memory groups of neurons throughout the neocortex that are involved at some moment in the (synchronized) processing the image of some local scene. That is, by strengthening the synapses among the neurons involved throughout the neocortex, the whole group tends to fire when some crucial group of them fires for some reason, recalling the local image.

The behavior generator for covert behavior receives the local image (and its telesensory images) by way of the projection from the entire posterior neocortex to the caudate nucleus of the corpus striatum. That is the perception of the object in space that is used to guide behavior. The corpus striatum also receives a projection from the entire anterior neocortex, which includes both its perception of its own body and the behavioral schemata contained in the frontal neocortex. The corpus striatum can project to both the ventral lateral and ventral anterior nuclei of the thalamus, but when behavior is covert, the projection to the ventral lateral nucleus is suppressed and only the ventral anterior nucleus is affected. The ventral anterior nucleus projects to the entire frontal neocortex (except for the motor neocortex itself and supplementary neocortex). Thus, when behavior is covert, the premotor neocortex and behavioral schemata located in the frontal area are both also projected to the anterior cingulate gyrus, and since the anterior cingulate neocortex projects to the posterior neocortex and, indirectly, to the local image, covert locomotion can call up images from memory in sequences, as required for spatial imagination.

The body image for overt behavior includes the motor neocortex, supplementary motor neocortex and somatosensory neocortex, all of which are organized somatotopically, like an image of the body. The overt bodily image is the source of motor commands to all parts of the body, but it is mediated by a projection (not depicted) from the overt body image to the cerebellum and its projection back to the motor neocortex by way of a part of the ventral lateral nucleus of the thalamus. (The cerebellum evens out the gross motor commands of the premotor and supplementary motor areas both spatially and temporally so that the precise motor commands work together smoothly in generating the prescribed behavior in the body as a whole.) This overt body image located in the neocortex is also the source of the input about bodily condition that is used to construct the local image. Its projection (via association fibers) to the inferior parietal neocortex is used to combine telesensory images as the local image representing the spatial relations among object in the current local scene relative to the body. Finally, the overt body image also sends a projection to the anterior cingulate neocortex, and since it projects to the posterior cingulate, the overt body image provides the labels for recording memory images according to the locomotion and turning that are responsible for them.

When behavior is being generated overtly, both parts of the circuits through the corpus striatum are active. A behavioral schema in the frontal neocortex is used to set up behavior in the premotor area, and when the signal (from the centromedian nucleus of the thalamus) to the putamen calls for the behavior to be generated overtly, the schema is used to send motor commands to the body. (The centromedian nucleus is in a position to tell when to generate behavior overtly, because it is at the center of the thalamic nucleus receiving processes from all its nuclei as the thalamus synchronizes processing in all parts of the neocortex.) When behavior is overt, the anterior cingulate gyrus receives input from both the overt and covert body images, and thus, the labels attached to memory groups that are formed when behavior is overt can be used to recall those images in sequence as spatial imagination when behavior is covert.

All the circuits combined are the subjective animal system of representation. The auditory system (in the superior temporal neocortex) and the tactile system (in the superior parietal neocortex) are not depicted.

All that is needed to complete the subjective animal behavior guidance system is the goal selection system. It is also a complete circuit through both the thalamus and the neocortex. The route from the neocortex back to the thalamus so that a circuit can be completed is provided in this case by the amygdala. Located in the anterior temporal lobe, the amygdala receives the same information from throughout the neocortex that the memory circuit receives by way of the hippocampus, except that it passes through an ancient form of cortex surrounding it (the piriform cortex). Thus, the amygdala is in a position to attach desires to the objects (or read affective labels already attached to objects) that are used by behavior schemata to generate behavior in relation to them. The amygdala projects to the dorsomedian nucleus of the thalamus, which projects in turn to the whole frontal neocortex. A diffuse projection to most of the frontal area is all that is needed to activate appropriate behavioral schemata. A denser projection from the dorsomedian nucleus is received by the orbitofrontal region, and it sends association fibers (by way of the uncinate fasciculus) back to the piriform cortex surrounding the amygdala. Thus, the goal selection circuit is able to make sure that desires are attached to the right objects.

Internalizing the spatial structure of the world. Even telesensory animals internalize a map of their territory. But their map plays very specific roles in generating complex, “hardwired” instinctive routines in telesensory animals. However, much of what is hardwired instinct in telesensory animals is learned by subjective animals from the environment. That is partly what makes the subjective level of neurological organization possible. As we have seen, what makes learning so much more important in subjective animals is a form of reproductive causation contained in individual brains with spatial imagination by which behavioral schemata evolve by reinforcement selection. (A similar mechanism has been described by Edelman, 1987, 1989, under the name of "neural Darwinism".)

The basic structure of the forebrain systems is set up in mammals by the biological behavior guidance system during embryological development, including the circuits of 2-D arrays that constitute the basic subsystems of the subjective animal behavior guidance system. But more neurons are created than are needed, and many neurons can make synapses more or less randomly with certain other neurons. The basic circuits line up 2-D arrays so that sensory input is registered in a way that can be used in generating behavior, and correspondingly, the mechanisms of the behavior generator are set up to make use of such sensory input in guiding behavior. But the specific neural connections needed to analyze and store sensory input in the most useful ways are lacking, and genetically prescribe behavior in response to sensory input is little more than reflexes built into in the behavioral output system and more or less random combinations of them.

Behavioral schemata in the behavioral output system evolve by a contained form of reproductive causation. As random variations on behavioral schemata are tried out, there is a natural selection of those that are successful in some way by a reinforcement that works through the memory circuit.

Though the memory circuit is depicted in the functional diagram as the basic structure of the sensory input system, it is realized in the brain in such a way that it is able to work the same way on neurons throughout the neocortex, including the behavioral schemata and body image in the anterior as well as the local image in the posterior neocortex. When some set of neurons is successful in some way, the memory circuit ties those neurons together in a memory group. That is, it instructs them to form synapses with one another so that if any crucial group of those neurons fire, the whole group will fire together. And with their synapses with one another strengthened, the whole group is more likely to be included as parts of other random variations on behavioral schemata.

Let us call such groups of neurons, which may be in the same 2-D array or in many different 2-D arrays, “memory groups.” Though the formation of memory groups depends on the memory circuit, once they are formed, they can be called up without any help from the memory circuit. The newly formed synapses among the neurons will make them act as a group when aroused by other neurons in the neocortex.

This increase in their likelihood of firing together again as a group is a form of natural selection of the group. It call it “reinforcement selection,” because the criterion for forming memory groups is, in mammals, the kind of desire satisfaction behaviorists were actually referring to in talking about reinforcement. The memory circuit is an ancient structure that includes the seat of desire, sometimes called the “limbic system,” and thus, success in satisfying desire in some way or other can easily be what triggers the formation of memory groups. In the case of learning behavioral schemata, success can easily be detected, for as we shall see, it is just success in internalizing some aspect of the world.

Mechanisms for identifying objects from the analysis of sensory input evolve in a similar way in the sensory input system. At the beginning of this phase of neurological development, groups of neurons respond to sensory input more randomly, and the memory circuit internalizes detailed structures that enable the sensory input system to recognize objects in sensory input and discriminate among them.

Telesensory input in any modality, such as vision or hearing, is registered in many different 2-D arrays. Those arrays may be determined to respond to them in different ways by the biological behavior guidance system, but the memory circuit, using built in criteria for success, can tie neurons together that are regularly active in processing sensory input in one way in one 2-D array with other neurons that are regularly involved in processing the same input in another way in another 2-D array. Thereafter, when sensory input is recognized in one 2-D array, such association fibers make it more likely that the input will also be recognized in the other 2-D arrays. Thus, processing in the various telesensory images work together to disambiguate sensory input.

At a later stage of neurological development, when mechanisms for recognizing objects of certain kinds have been established, this mechanism can also be used to identify particular objects. Different objects of similar kinds can be distinguished by tying a general memory group together with additional neurons in various 2-D arrays that are distinctive of it in a new memory group.

When new sensory input causes patterns of neuronal firings in many different 2-D arrays of the sensory input system that conform to such a memory group, the memory group is activated, and the sensory input system settles into equilibrium. (Since these areas of neocortex are all coordinated by the thalamus, such a settling into equilibrium may be what causes the distinctive “gamma oscillations” that are detected by EKGs when objects are recognized.)

For our purposes, what is most relevant about this contained form of reproductive causation is how the evolution of behavioral schemata internalizes the spatial structure of the world as the structural cause of spatial imagination. Though the behavioral schemata are certain groups of neurons in the frontal neocortex that the behavior generator uses to issue motor commands from the body image, what evolves are neural connections throughout the neocortex, because motor commands must be generated in relation to sensory input. These groups of neurons are the “organisms” (or primary structures) that evolve, because they are what go through reproductive cycles and have both essential structural effects. Random variations on them are naturally selected by success in reproduction, though in this case reproduction occurs when they generate overt behavior and it is reinforced through the memory circuit.

The basic schema has the part-whole complexity required of an organism that can evolve, since it is made up of motor commands to different parts of the body as well as different sequences of such sets of motor commands in time. Thus, many varieties of the basic schema are possible.

These schemata also do both kind of work that are required for organisms to evolve. Their non-reproductive work is the behavior they generate in relation to sensory input when they are firing. And they reproduce when the groups of neurons involved are signaled to strengthen and extend their synapses, that is, are reinforced for working together in the various circuits of 2-D arrays in a way that satisfies desire.

Thus, behavioral schemata evolve gradually, starting off simple, uniform and weak, and becoming complex, diverse and powerful. The ecological niches to which they adapt are all the various situations in which some special kind of behavior in response to sensory input is needed to satisfy a desire, that is, are reinforced.

Memory groups for identifying the telesensory images for situations in which behavior is reinforced are part of the selected behavioral schemata, that is, like discriminative stimuli. But since it is a faculty of spatial imagination, connections are also established between telesensory images and behavior that work the other way, so that when the behavior is generated covertly, telesensory images representing its effects are called up from memory.

In order to construct even a local image, the telesensory input must be registered in a way that indicates the bodily condition at the time, such as the direction the head and eyes are pointing when visual input is registered. That is a regular relationship in any given local scene viewed from a certain location, and thus, the memory circuit can establish their neural connections as a memory group. But in order for them to serve as a local image that can be recalled from memory, it must be possible for the behavior generator to use the combination of telesensory images recorded in memory as a local image to anticipate what telesensory images will occur when it behaves in various way, and that is a result of the evolution of behavioral schemata in the behavior generator.

Starting with whatever behavioral schemata are built into the behavior generator genetically, such as standing up, walking, focusing eyes together on an object, behavioral schemata for more complex or more precisely controlled behavior can be acquired by reinforcement selection of random variations on them. But since telesensory images are recorded in the local image according to the bodily condition at the time, schemata for generating those bodily conditions become labels for calling up those telesensory images in imagination. Thus, as behavioral schemata evolve, the subjective animal learns the motor commands to use in moving its head and body in order to make an object that appears to the right visual field move to the center of the visual field.

Though local images vary with the local scenes they represent, the same behavioral schemata for calling up particular telesensory images from them will work for them all, because bodily movements have similar effects in all situations. The behavioral schema that evolves for that function becomes, in effect, the structure for recording all local images, and the covert behavior for generating bodily conditions become labels for calling up the telesensory images in different directions. Thus, the evolution of behavioral schemata internalizes an aspect of the spatial structure of the world.

Once the ability to construct and recall local images has been acquired, much the same kind of process will internalize the structural causes needed to link them in sequences as a map of its territory (assuming that the cingulate gyrus contains a mechanism that can link memory groups in sequences). Given that behavioral schemata for locomotion and turning in relations to perception have been acquired, the key to spatial imagination is recording and recalling entire local images in a way that corresponds to such behavior.

Starting from a certain local scene in the territory, the effects of locomotion and turning on the local images encountered are determined by the spatial structure of the actual world. Thus, assuming that the memory for sequences of local images (in the cingulate gyrus) receives input about its overt locomotion and turning, its neural connections to the resulting changes in local images become labels for recording and recalling local images as a map of the territory. Using those behavioral schemata to generate covert locomotion and turning in relation to a given local image would, therefore, enable the subjective animal to explore the map of its territory.

Once again, however, the same kinds of behavior, turning and locomotion, work much the same way in any local image of the territory. Thus, as these behavioral schemata evolve, the memory for sequencing local images (and for shifting from one sequence to another when the body turns in a different direction) acquires labels that are used for every local image. That is a general understanding of the structure of space in terms of the effects of motion, and it informs even the local image, that is, enables the subjective animal to see its telesensory input from objects in the local scene as spatial relations that can change by motion. For example, as it learns to register local images according to turning, it learns that turning far enough brings it back to the same direction, and it can come to see how it would have that effect even in the local image.

The capacity to acquire structural causes from the environment eases the burden on the biological behavior guidance system to provide structural causes, but once the basic structure of the mammal’s higher level of neurological organization had been selected, evolution by reproductive causation would provide the additional structures needed to make this learning mechanism more efficient and complete.

The representation of the local scene is, in effect, a representation with polar coordinates, whereas the memory map of all the salient objects in the territory uses, in effect, Cartesian coordinates. This translation between polar and Cartesian coordinates is mathematically too complex to be provided genetically, but it can be acquired from experience. As the mammal experiences the consequences of moving in different directions from the local scene and finds the same objects showing up as a result of different combinations of bodily movements, behavior schemata for turning and moving in each direction evolve, so that later they can be used by the behavior generator as labels (in the anterior cingulate) to switch from one sequence of local images to another in exploring its subjective map. The mammal discovers, for example, the direction in which the body winds up moving as a result of various combinations of bodily movements, such as turning, backing up, rolling over, and the like, and so those combinations become packaged as behavioral schemata, or possible intentions, to move in certain ways in local scenes. They provide the translation from the "polar coordinates" of the local image to the Cartesian labels of the memory map. Only when a young mammal has learned the effects of turning and locomotion in the local scene is it able to start using the memory circuit to construct its own 3 .D memory map of the territory.

The origin and detailed structure of the mammalian brain. Assuming that much of the detailed connections among neurons can be acquired from the structure of the world by experience, or learning, all that is needed for telesensory vertebrates to try out the higher level of neurological organization required for a subjective animal system of representation is a random variation that sets up the basic circuits depicted in the functional description of the behavior guidance system. By considering the structures of the non-mammalian and mammalian vertebrate brains, we will see how it can be accomplished by a relatively simple, albeit radical, the random variation. That description of the basic structure of the mammalian brain also reveals the detailed neural mechanisms that serve the various functions in the subjective animal behavior guidance system.

In the non-mammalian vertebrate brain, as we have seen, the three subsystems serving the three subfunctions of the animal behavior guidance system are distributed to three anatomically distinct regions of the brain, the segment of nervous system rostral to the spinal chord, which connects the brain to the body. Those regions are the forebrain, midbrain and hindbrain.

Any behavior guidance system, as we have seen, must register sensory input from the world, select from among incompatible kinds of behavior, and generate the kind of behavior chosen. In the vertebrate brain, sensory input is registered in the midbrain, selection among incompatible kind of behavior is mainly the responsibility of the forebrain, and behavior is generated by the hindbrain. Connections between the midbrain and hindbrain enable them to serve as the telesensory animal system of representation.

The transformation of the non-mammalian into the mammalian brain is often described as the centralization of functions in the nervous system. That is, the three subfunctions of the animal behavior guidance system, which are parceled out to the three anatomically distinct sections of the non-mammalian brain, are all served by one of those sections in mammalian brains, namely, by the forebrain.

It is obvious that the mammalian forebrain serves the output subfunction, since motor output is generated directly from the neocortex, a distinctively mammalian structure in the forebrain. (Motor output from the hindbrain, which generates motor output in non-mammalians, is fully under its control.) Muscles throughout the body are controlled by a somatotopically organized 2 .D array of neurons in the motor neocortex.

Although visual input is already received by the forebrain in non-mammalians (along with the optic tectum in the midbrain), it is joined in mammals by well defined relays to the neocortex for auditory and somatosensory input (all three via nuclei in the thalamus).

Since the subfunction of selecting goals for behavior is already contained in the forebrain, it is apparent that the mammalian forebrain is using its sensory input to generate motor output, thereby serving all three subfunctions. Hence, it is the mammal's entire animal behavior guidance system.

The shift of all three subfunctions from the three distinct parts of the non-mammalian brain to the forebrain resembles the evolution of the vertebrate brain from brainless chordates: just as the rostral end of the chordate neural tube became a brain that took over the control of behavior from reflexes located throughout the neural tube, so the mammalian forebrain takes over the control of behavior from the midbrain and hindbrain. The midbrain and hindbrain structures are still there, but they are slaves to the forebrain (and are omitted from the mammalian diagrams unless they play an essential role).

Furthermore, the neural connections among the subsystems in the mammalian brain are just what would be expected of an animal system of representation with spatial imagination. We have seen functionally how the subjective animal system of representation requires four subsystems (the local image, body image, behavior generator, and memory), and the simplest and most convincing way to show how their functions are served by structures in the mammalian forebrain will be to describe how those mammalian structures evolve from simpler mechanisms in the non-mammalian forebrain. The relevant structures of the vertebrate brain have already been described (see Stage 5. Telesensory animals: Structure of the non-mammalian vertebrate brain).

There are, as already mentioned, two kinds of changes in the non-mammalian forebrain that result in mechanisms for the subjective animal system of representation — the evolution of the neocortex, and a restructuring of the thalamus that redirects the non-mammalian forebrain output back to the (telencephalon of the) forebrain (by way of the thalamus) to form the complete circuits of its higher level of neurological organization. The first change occurs in the telencephalon of the forebrain and the second in the diencephalon.

The neocortex evolves from the integration of the DVR and dorsal cortex, the two main telencephalic targets of thalamic nuclei in reptiles. During embryological development in mammals, cells in the telencephalon that would become the DVR in reptiles migrate to the dorsal cortex (the extended flap of neural tube at the diencephalon) and lay themselves out in the dorsal cortex against the outer surface of the mammalian telencephalon. The result is the six layers of cells distinctive of mammalian neocortex. (Compare the diagram of the reptilian brain with that of the mammalian brain.^xv) The evolution of the neocortex adds to the telencephalon a somatotopic representation of the body (the body image) and all the telesensory images that make up the local image.

The thalamus is restructured so that it redirects the non-mammalian forebrain's three kinds of output back to the telencephalon, and this results in the creation of three circuits in the mammalian forebrain. Each circuit is a pathway of neural projections that includes both the thalamus and the neocortex along with special structures that make them different from one another. And each circuit serves one of the basic subfunctions of the animal behavior guidance system. The sensory input circuit serves as local image with the memory in the functional diagram. The behavioral output circuit combines the systems labeled body image and behavior generator in the functional diagram. The third circuit is the affective system, for selecting goals of mammalian behavior, which attaches desires to objects in the local image by activating dispositions in the behavior generator.

Since the neocortex and thalamus are what are linked by the three circuits, these two main changes are connected. Each of the areas of neocortex and nucleus of the thalamus is on roughly the same level of neurological organization as each of the basic systems making up the telesensory animal behavior guidance system, and thus, when they are linked in a three different circuits, each serving one of those subfunctions, there is obviously a higher level of neurological organization. But the best way to see how this basic structure is tried out is to start with the change in the thalamus that gave the neocortex a somatotopic representation of the body to serve as the behavioral output system of the subjective behavioral output system.

The body image. Motor output is generated from the body image, a region of the neocortex that is somatotopically organized. It receives somatosensory input from all parts of the body and it generates the motor output controlling all parts of the body. Like the local image in the posterior cerebrum, the body image is a region of neocortex located in the anterior cerebrum. But somatosensory and motor neocortex represent the body like a picture (or, rather, several pictures), and a somatotopic organization is such a highly improbable mechanical order that the behavioral output system is a good example of a complex structure that seems unlikely to be tried out as a random variation by the mechanism of embryological development. But it most come from somewhere.

The image of the body in the neocortex cannot come from either of the geometrical structures from which the neocortex evolved, because neither the DVR nor the dorsal cortex have a somatotopic organization. But telesensory animals needed such a somatotopic representation of the body in order to even out motor commands to muscle groups in each region of the body so that whole body behavior would be coordinated. That requires the command neurons to be related spatially to one another corresponding to spatial relations among the parts of the body they control, and that was the function of the cerebellum.

Even before reptiles, there was a rough somatotopic organization in the cerebellum (the archicerebellum), but the evolution of legs required a more distinct somatotopic organization. As mentioned above, it is found in a new region of the cerebellum (the paleocerebellum) and in the red nucleus to which it projects in the midbrain in order to affect motor commands to the limbs.

There is a further development of a similar kind in the mammalian cerebellum. Yet another region is added to the cerebellum (the neocerebellum). The mammalian cerebellum projects to the red nucleus and (joined by a projection from the red nucleus) to the motor neocortex (relayed in both cases by a new nucleus of the thalamus, the ventral lateral nucleus). In other words, the red nucleus now sends motor commands to the limbs by way of a somatotopic representation in the neocortex. (See diagram of the behavioral output system.) This relay of its output to the motor neocortex required a new nucleus in the thalamus, and that may have been the original random variation that is responsible for both the reorganization of the thalamus and the neocortex.

Not only does it locate a somatotopic behavioral output system in the neocortex, but it is also the source of the somatotopic organization of somatosensory input to the neocortex (which is also relayed to the neocortex by a new thalamic nucleus, the ventral posterolateral nucleus).^xvi In primitive mammals, such as the hedgehog, somatosensory input and motor output share the same body image in the neocortex, and only later do their images come to occupy adjacent areas of neocortex across the central sulcus.

The local image. The telesensory images making up the local image are on the same level of part-whole complexity as the body image. Both are regions of neocortex receiving highly organized 2-D projections from specific nuclei of the thalamus. As in earlier vertebrates, telesensory input is relayed to the telencephalon by nuclei in the thalamus. Visual input is relayed by the lateral geniculate body to the occipital neocortex, and auditory input is relayed by the medial geniculate body to a region of the temporal neocortex. But the evolution of the neocortex provides a more powerful mechanism for its analysis than in telesensory animals. (See the diagram of the local image.)

Regions of neocortex all have a similar structure. Thalamic neurons send axons in ordered, 2 .D arrays to certain 2-D areas of neocortex where they synapse with certain kinds of neurons (that is, with neurons in one or another of its six layers). And neurons in target areas of the neocortex send 2 .D arrays of axons to three kinds of targets in the forebrain: directly back to thalamic nuclei, to other neocortical areas, and to the corpus striatum and its special projection to certain thalamic nuclei (behavior generator). These connections are determined genetically, by instructions from the multicellular biological behavior guidance system. It is a good example of the more complex structures that can develop from the neural tube in deuterostomes: neurons in the thalamic nuclei and their neocortical targets are born with molecular labels by which they can somehow recognize their own locations in their own 2 .D array and seek out corresponding locations in other 2 .D arrays.^xvii

In the case of telesensory images, all the 2 .D arrays in the thalamus and neocortex are usually processing sensory input from the same objects in the local scene at any given moment, but following genetic instructions to analyze it in different ways. With evolution by reinforcement selection, therefore, they can use the results of one another's analysis to confirm their own conclusions, thereby improving the efficiency of them all.^xviii Jointly, they are a subsystem with a 2 .D representation of the object at a distance.

The local image is, however, a more encompassing 2-D representation of the current scene, which includes all the currently perceivable objects relative to the body. The local image is constructed by an interaction between the body image and specific telesensory representations. The local image is constructed in a region of neocortex (the inferior parietal lobe) adjacent to the visual and auditory analysis areas, on one side, and the body image, on the other, and it receives association fibers from both sides. (See diagram of the local image.) The image of the body in the motor and somatosensory neocortex projects association fibers providing information about the current bodily condition (its stance and motion), and the parietal area uses it to locate objects of telesensory images in the scene relative to the body by taking account of the direction in which the head and ears are pointed when they are received.

The eyes are, however, a special case. Their fixations are controlled by the frontal eye fields (an area of frontal neocortex, anterior to the motor cortex, which we are counting as part of the behavioral output system). The frontal eye fields also report their oculomotor commands to the inferior parietal lobe (via association fibers), where an interaction with the visual neocortex (in the occipital area) constructs a larger representation of the scene (the local image) from the visual images that show up in each fixation.^xix (See diagram of the local image.) The already constructed local image guides the fixations of the eyes to objects in the scene; that is apparently the function of a highly unusual, ordered 2-D projection of fibers to the frontal eye fields from the thalamic nucleus (pulvinar) that serves the inferior parietal area.^xx The local image is not, therefore, just a collection of telesensory images, but an ordering of them that indicates the direction and distance of each from the body, or what serves as representation of the current local scene.

Touch is a new sensory modality, which depends on a certain kind of somatosensory input to the body image. As we have noticed, somatosensory input is relayed (by the posterolateral nucleus of the thalamus) to the somatosensory neocortex (across the central sulcus from the motor neocortex), where reports from joint and muscle receptors supplies feedback about the effects of motor commands from the body image. But it is also, in effect, a new sensory modality, because input from skin receptors (of various kinds) is combined with the representations of the scene and the body (in the superior parietal area served by the lateral posterior thalamic nucleus) to yield information about other objects in the current scene (though this does not yield much information about them except location until the evolution of manipulative animals). (See diagram of local image.) Since the objects are distinct from the body, but located not at a distance for it, touch might be called an "extrosensory modality."^xxi

The evolution of the neocortex, in sum, accounts for one part of each of the two basic subsystems of the subjective animal system of representation, the sensory input and behavioral output systems. Almost every area of neocortex receives a projection from one or more thalamic nuclei (and sends fibers back), but the body image is located in the anterior neocortex, and the 2 .D telesensory images of the objects in the scene and their combination as a local image is located in the posterior neocortex. But these regions of neocortex act on the thalamus in two different ways, each of which makes the neocortex a link in a complete circuit. The rest of each circuit is the other part of the sensory input and behavior output systems represented in the functional diagram of the subjective animal system of representation, and that is the part of each circuit that is provided by the other major change in the mammalian forebrain, the redirection of the output of the non-mammalian forebrain back to the telencephalon by relays in the thalamus. (The same also holds for the goal selection system, the third part of an animal behavior guidance system, as we shall see.)

We have seen that there are three pathways of output from the non-mammalian forebrain: the ancient olfactory pathway, the striatal pathway, and the hippocampal pathway. And each is responsible for a new, complete circuit in the mammalian forebrain. Indeed, the functions are parceled out to these circuits according to the three subfunctions of any behavior guidance system.

The striatal pathway becomes part of the behavior generator which works together with the body image to serve as the behavioral output system.

The hippocampal pathway becomes the memory which works together with the local image to serve the sensory input subfunction of mapping the territory.

And the olfactory pathway becomes the goal selection system which works together with both frontal and posterior areas of neocortex to serve the subfunction of selecting goals,. We will put the olfactory pathway aside for now and take it up only after detailing the subjective animal system of representation, because the subjective animal behavior guidance system is what results when olfactory pathway is added to the subjective animal system of representation. Let us begin with the hippocampal pathway and how memories are recorded.

The memory. The mammalian memory is a forebrain circuit that results from redirecting the hippocampal output of the non-mammalian forebrain back to the telencephalon by way of another new thalamic relay (the anterior nucleus) in the diencephalon. Its target is, however, a new region of neocortex, the cingulate area, which runs parallel to all the other areas of the neocortex at the medial extreme of the neocortex (including the local image, body image, and other regions of frontal neocortex where behavioral schemata are located. See diagram of the memory.) This provides a new, complete circuit, because association fibers connect the cingulate area with all the areas of neocortex running parallel to it, and those areas all have association fibers to (a staging area in the temporal lobe that projects to) the hippocampus. Since the hippocampus receives information about the "images" in 2-D arrays throughout the neocortex, it is what enables the mammalian brain to learn from experience with the three dimensional structure of the world how to use the input about the body condition (association fibers from the behavioral output system to the parietal cortex) to construct the representation of the local scene and how to label such representations by their locations relative to one another in three dimensional space as it forms new memory.

The basic mechanism involved in the formation of memories is the strengthening of synapses of association fibers connecting sets of neurons in various regions of the neocortex that are firing at the time, so that later, when enough of them fire together again, it makes the others in the group fire as well. Although synapses are strengthened anyway among 2-D arrays in nearby areas of neocortex that are closely interconnected,^xxii the hippocampus-cingulate circuit connects, as memory groups, neurons from all areas of neocortex that are active at the moment.^xxiii This connects images of the same object from different sensory modalities as the same object and images of various objects in the current scene as a local image so that they can be called up together as units. But it is necessary to have input about the current bodily condition to label telesensory images by the behavior involved in perceiving them in the scene. That is provided by association fibers from the behavioral output system to the inferior parietal neocortex, and if input from the bodily condition is not what is combined in the memory groups for the local image, it must be the relevant groups of neurons of the behavioral output system itself.

Given how the memory system (the hippocampus-cingulate circuit) works, it is required to form such cortex-wide memories. But it is not involved in recalling memories. Recalling memories is simply a matter of making the whole group fire together by enough of its members firing for some reason.^xxiv

Indeed, at an earlier stage of embryological development, as mentioned above, the memory circuit is responsible for acquiring the behavioral schemata by which overt inquisitive behavior can construct local images and similar covert behavior can extract information about the locations of objects in the local science from local images called up from memory. The memory circuit provides the “natural selection” for a contained form of reproductive causation in which the “reproducing organisms” are connections among neurons serving as behavioral schemata, neurons representing the bodily condition, and neurons serving as telesensory images, and these connections evolve as parts of schemata that the behavior generator can use, as inquisitive behavior, to construct local image, or as covert behavior, extract information about them. The correlations between telesensory input and bodily condition that hold for objects of every kind in any local scene depend on the structure of space (and the structure of the body driven by the brain), and the memory circuit enables the brain to acquire the general connections between cells in the local image and body image so that behavior schemata for constructing and using local images can evolve by the natural selection of a reinforcement that strengthens the connections when they are successful, for example, when the animal can find objects it desires in the scene. Thus, the structural cause of the capacity to record and use local images is internalized from the structure of the spatiomaterial world by a form of reproductive causation that occurs as a later phase of the process of the embryological development of the brain.

There is evidence, by the way, that the schemata for this kind of behavior is derived from experience. When human subjects are fitted with glasses that reverse right and left or up and down in the visual field, there is, after a long period of awkward attempts to compensate, a dramatic change in which subjects report that everything "suddenly" seems oriented in the "right" direction again. As the memory circuit lays in new connections for behavioral schemata to construct and use local images with the reversing glasses and they take over, one's sense of direction changes.

The memory circuit also has a built-in structure that makes it possible to connect local images in sequences corresponding to the direction of locomotion and turning relative to them, though linking them in such sequences depends on the cingulate neocortex functioning in an additional way. When the cingulate neurons in a memory group fire, so do the associated images in the adjoining regions of neocortex, and vice versa. The means that the cingulate neocortex is in a position to determine the local images called up in sensory input system. Thus, in order to serve as the memory for spatial imagination, all the cingulate gyrus needs is the capacity to link local images together in long sequences and to be able to switch from one such sequence to another when their local images overlap.

The posterior cingulate gyrus is in a position to serve as the memory for spatial imagination, because the posterior cingulate receives input about the bodily condition, overt and covert, from the anterior cingulate gyrus. The anterior cingulate gyrus is connected to the body image and the behavioral schemata in the behavior generator in a way that is similar to the connection between the posterior cingulate gyrus and the local image, except that the influence runs the opposite direction. The body image and behavioral schemata project to the anterior cingulate gyrus, and the anterior cingulate gyrus is an (agranular) motor neocortex like the body image and behavioral schemata, except that it has not effect on overt motor output and projects to the posterior cingulate gyrus.

Since the body image contains information about how the body moves and turns overtly in the scene, the connections it makes with the posterior cingulate gyrus would become labels that are recorded with the sequences of local images. And since the behavioral schemata contain the same kind of information about covert behavior, and it is projected to the posterior cingulate gyrus in the same way, those connections can be used as labels to call up the local images according to how it move and turns covertly in relation to the images called up in memory.

As sequences of local images become richly interconnected, the mammal acquires a map of its territory by which it can travel almost any route. It is the structure of space that ensures that such interconnections of sequences can accumulate without contradictions. This internalization of the structure of space is an example of the a contained form of reproductive causation that takes place in neurological development as a result of reinforcement selection. The memory labels required for constructing and exploring memory maps are part of the behavior schemata that evolve gradually toward greater efficiency in satisfying desires, in the first instance, getting the animal where it wants to go.^xxv

The behavior generator. In reptiles, the DVR is the main source of input to the striatum (which is one pathway of non-mammalian forebrain output to the midbrain), and thus, since those DVR cells migrate in mammals to the dorsal cortex and combine as the neocortex, the neocortex becomes the main source of input to the striatum (called the corpus striatum or basal ganglia). In fact, all areas of the neocortex project to the corpus striatum, including the local image, the body image, behavioral schemata in the frontal neocortex, and the cingulate neocortex. But the output of the corpus striatum, which in reptiles was projected to the midbrain as motor commands, is mostly redirected in mammals back to the neocortex by way of a relay in the thalamus (the ventral lateral and ventral anterior nuclei). The targets of the corpus striatum are all in the frontal neocortex (in the anterior forebrain), including both the body image and the behavioral schemata. This new circuit is the behavior generator. But there are two channels through this circuit, which were not distinguished in the functional diagram except for the ability to generate behavior either overtly or covertly.

Part of the corpus striatum's output is relayed by the (ventral anterior) thalamus to regions throughout the frontal neocortex where the behavioral schemata are located. This part also projects to a region called the “premotor cortex” (an anterior part of Brodmann area 6), which is the behavioral output system for covert behavior. It also projects to the frontal eye fields, which controls the fixation of the eyes on objects in the local image.

The other part of the striatum’s output is relayed by the (ventral lateral) thalamus more specifically to the motor neocortex itself, the part of the body image that is responsible for overt behavior. This includes both the motor neocortex (Brodmann area 4) the supplementary motor neocortex (an area of neocortex adjacent to the motor neocortex which modifies motor commands directly, which is part of Brodmann area 6.)

The motor neocortex (the body image from which overt behavior in generated) also receives a projection from the ventral lateral thalamus that relays the output of the cerebellum (where motor commands are evened out spatially and temporally in a detailed way). The motor commands actually sent to the body depend, therefore, on the cerebellum as much as the circuit through the corpus striatum and ventral lateral thalamus. But the cerebellum is controlled by these circuits through the striatum and thalamus, because the cerebellum follows motor commands from the body image, including both parts, Brodmann areas 4 and 6. (The premotor commands, a part of the body image that generates covert behavior, enables the cerebellum to anticipate the next overt motor commands.)

The corpus striatum has just the connections required of a subsystem whose function is to generate behavior in relation to the object at a distance. It receives 2 .D arrays of fibers from all areas of the neocortex, including the local image in the posterior neocortex, on the one hand, and the behavioral schemata and body image (both premotor and motor areas) in the anterior neocortex. But it projects only to the behavioral schemata and the body image in the anterior neocortex. (See diagram of the behavior generator: overt behavior.)

The local image sends fibers almost exclusively to a distinct part of the corpus striatum called the caudate nucleus. The caudate nucleus apparently compiles an image of the object situated in the current scene from all parts of the posterior neocortex, because 2 .D arrays of posterior neocortex that are connected by association fibers tend to converge on the same areas of the caudate nucleus.^xxvi

Similarly, the body image send fibers almost exclusively to a distinct part of the corpus striatum, called the putamen. The putamen compiles an image of the body from all areas of the anterior neocortex, including the frontal areas containing behavioral schemata and the body image, for it merges 2-D arrays from parts of neocortex that are closely connected by association fibers. With behavioral schemata contained in the frontal neocortex, the putamen has instructions by which to generate a specific kind of behavior (depending on which desire predominates at the moment).

A third distinct part of the corpus striatum, called the globus pallidus, combines the compiled image of the body with the compiled image of the object according to the selected schema to produce detailed motor commands for each part of the body as needed to adjust its behavior to the object in space.^xxvii The globus pallidus can generate behavior, because it projects by way of nuclei in the thalamus to areas of premotor and motor neocortex that are responsible for motor commands to all parts of the body.

For the animal system of representation to have a spatial imagination, however, the behavior generator must be able to generate motor commands in relation to objects in the scene without the body actually acting on them. And the corpus striatum does, indeed, have connections that make it possible to generate behavior covertly rather than overtly. There are two distinct channels by which the corpus striatum projects to the thalamus (and from there back to the neocortex, which completes a circuit because of the cortex’s projection to the corpus striatum). (Both originate in the internal segment of the globus pallidus, the third part of the corpus striatum, where both the local image and body image are represented).

One channel (by way of the ansa lenticularis) projects to the ventral anterior nucleus of the thalamus which relays it to the premotor and other frontal areas of neocortex where behavioral schemata are contained. These areas of neocortex project in turn to the anterior cingulate gyrus, whose connections with the posterior cingulate gyrus enable covert behavior to affect the sequences of images in memory.

The other channel (by way of the lenticular fasciculus) is relayed by the ventral lateral thalamic nucleus to the supplementary motor neocortex, which lies alongside the motor neocortex and generates overt behavior. (The ventral lateral nucleus also relays the detailed motor instructions from the cerebellum and red nucleus, but that is a later effect of this circuit for overt behavior through the striatum and thalamus, because its motor commands are what the cerebellum uses to work out the detailed motor commands.) These areas of the body image also project to the anterior cingulate gyrus, where they can establish labels for the sequences of local images in spatial imagination.

Both channels of the are active when behavior is overt. The covert route is never suppressed, because it is the circuit that contains the behavioral schemata and uses them to set up complex, multi-step motor commands in advance of acting. But when the channel to the motor neocortex is suppressed, behavior is generated covertly, as imagination, because the anterior cingulate gyrus still receives the projection from the behavioral schemata and premotor cortex. That is enough information about locomotion and turning to call up memories of local images by the labels that were established when both overt and covert parts of the body image were being projected to it.

The subjective animal’s behavioral output system has, therefore, two body images. Both are used for generating overt behavior, but one can be used for generating covert behavior. Covert behavior is the motor output in the cingulate gyrus, which acts, not on the actual world by way of the body, but on the world as represented in memory by way of covert behavior. Since the anterior cingulate gyrus projects to the posterior cingulate gyrus in much the same way that the motor neocortex (and associated areas) project to the parietal and sensory neocortex containing the local image, it is not surprising that the memory circuit can register images according to the behavior that causes them, that is, by labels. Nor is it surprising that covert behavior can use those labels to call up the images from memory as imagination.

The difference is that telesensory images are registered according to input from the overt bodily condition so that they become a local image, which can be recorded as a unit in memory, whereas local images are registered according to input from the overt locomotion so that they become linked in a sequence as a map of the territory. One occurs in the non-cingulate region of the neocortex, the other occurs requires the cingulate area. Likewise, when a local image is remembered, its individual telesensory images can be called up by input from covert behavior in the non-cingulate neocortex, whereas other local images connected to it can be called up by input from covert locomotion in the cingulate gyrus.

This parallel suggests that labels can be established in both cases by the memory circuit working as a form of reinforcement selection for the evolution of behavior schemata. The labels are simply connections of the behavioral schemata with the rest of the brain that are reinforced as parts of those schemata when behavior is overt, and thus, since the behavioral schemata can be used to generate the same behavior covertly, they automatically have labels by which to call up the relevant images from memory.

What is crucial to internalizing the structure of space as spatial imagination about the consequences of locomotion and turning is the capacity of the cingulate gyrus to link complex memory groups in sequences. That is what the non-cingulate neocortex lacks. Sequences of images are not needed to construct local images, because they can be accessed in any order by the appropriate bodily condition, turning the head, eyes, etc. But it is the use of sequences, and their being projected to the behavior generator (via the caudate nucleus of the corpus striatum) as time passes, that makes it possible to imagine locomotion and motion. And that is the key to their being an understanding of the structure of space. This is a capacity to see the actual locations of objects against the background of what is possible by motion, which is to understand the structure of space.

The subjective animal’s map of the world becomes an understanding of space simply because the same kinds of locomotion and turning have the same kinds of effects relative to any set of local images. That is because the world from which those sequences were recorded is a world of objects that are actually related by being contained by space. Thus, experience with the world gives the subjective animal is understanding of the general effects of the motion and direction of motion of an object on its spatial relations to other objects. It is, of course, an intuitive understanding, not a linguistic understanding. But it is nonetheless an understanding by which it can foresee what will happen and understand what has happened.

More generally, however, the power of the memory circuit as a form of natural selection on behavioral schemata working by the reinforcement of synapses to form memory groups is broader. Assuming that during the process of development, the whole range of behavioral schemata that are possible because of the genetically provided basic schema are tried out, gradual evolution will occur, and the schemata will becomes increasingly powerful. Each behavioral schema will come to be as effective as possible in controlling some relevant condition, that is, generating behavior is some kind of situation to satisfy desire. That is actually the result of the gradual evolution of that schema, since it is made up of different motor commands as parts, and it is by alterations in them that variations are tried out. But different behavioral schemata will also be fit together as harmoniously as possible as parts of behavioral routines that satisfy desire. And new schemata will be added as long as they control additional conditions that affect their reproduction. Thus, learning from experience that provides subjective animals with behavioral schemata for many kind of behavior. The schemata that serve as structural causes for spatial imagination is just the most important kind of behavior, given the nature of the world in which animal find themselves and their need to act on objects in space.

This theory of imagination as covert behavior offers a plausible explanation of schizophrenia. Hallucinations that are not recognized as hallucinations (usually auditory hallucinations) are the main symptom of schizophrenia. They make it difficult for schizophrenics to tell the difference between fantasy and reality. It is known that schizophrenics often show a lack of activity in the frontal neocortex when hallucinating (apparently due to an unusual level of the neurotransmitter, GABA, in the region). Those areas of neocortex contain the behavioral schemata that control the anterior cingulate gyrus, whose effect on the posterior cingulate is to call up images from memory, and thus, it is possible that schizophrenia is a condition in which covert behavior is generated without control by behavioral schemata in the frontal neocortex. Since the images are not called up by activating some behavioral schema, as in normal behavior and imagination, they are not part the process of carrying out an intention, and thus, they seem to originate from the world, that is, to be real.

The goal selection system. Not only does reproductive causation in neurological development require reinforcement, but once animals have acquired a map of the territory and an understanding of the structure of space, they still need a mechanism to choose which goal to pursue in relation to which objects. These functions are served by the redirection of the third output of the non-mammalian forebrain back to the telencephalon. The redirection of the olfactory pathway back to the telencephalon makes it the goal selection system of the mammalian behavior guidance system.

The olfactory pathways involve, as described in the non-mammalian vertebrate brain,^xxviii the amygdala and its many connections with the hypothalamus (and septum). This is still the seat of desire in mammals. The amygdala is mainly responsible for arousal, fear and anger, whereas the hypothalamus is responsible for hunger and sexual desire.

In mammals, the output of the amygdala (and indirectly the hypothalamus) is redirected by a thalamic nucleus (the dorsomedian nucleus) back to the behavioral schemata in the frontal neocortex (especially, the orbitofrontal area). This system selects which of the schemata for kinds of behavior that are built into the frontal neocortex (genetically or by learning) will guide the corpus striatum in generating behavior relative to the object in the local image.

The goal selection system is a complete circuit, for there are projections from the orbitofrontal area back to the amygdala (via the ancient piriform cortex surrounding the amygdala) which make sure that there is no confusion about which object is the object of desire.

Furthermore, the goal selection circuit is in a position to record and read desire labels with memory images. The amygdala has a projection to the hippocampus by which it can attach desire-labels to objects (for example, when the hypothalamus reports to the amygdala that an object satisfies hunger or sexual needs), and it can read the desire-labels already attached to objects, because it receives a projection from the staging area by which all areas of neocortex reach the hippocampus. (See diagram of the goal selection system.^xxix)

A desire about an object sets a problem for the subjective animal system of representation to solve. Covert locomotion can, for example, explore its map and figure out a new route to an unperceived goal when its path is blocked or use its representation of the current scene to figure out how to approach or avoid some object. But a spatial imagination is only part of what is possible for a system that uses a somatotopic representation of the body to generate behavior by its parts, like the body image. Instead of having to evolve new instincts, it can learn new kinds of behavior involving different combinations of motor commands to parts of the body. And mammals can, in principle, figure out how to use such complex routines in the current scene by imagining variations on them and using memory images that are called up to anticipate whether the consequences will satisfy its desire. At least, this is the direction of subsequent evolution, as we shall see.

Acting. Once the problem is solved and a plan of behavior has been selected, the imagined behavior must be generated overtly. Covert behavior depends on one of the pathways through the behavior generator (the one from the corpus striatum via the ansa lenticularis to the ventral anterior nucleus of the thalamus and back to the frontal neocortex and premotor area). The behavioral schema that has been set up in imagination can be generated overtly by sending the same motor commands in relation to the perceived object along the other pathway as well (via the lenticular fasciculus to the ventral lateral nucleus back to the motor cortex).

What controls whether covert behavior is generated overtly or not is the centromedian nucleus of the thalamus. It projects to the putamen, the part of the corpus striatum that receives the schema from the frontal neocortex for the kind of behavior to be generated. The centromedian nucleus is located within the medullary lamina of the thalamus (separating its medial and lateral subdivisions), and since the thalamus is what synchronizes activity throughout the neocortex, that is a position from which it can to tell when an equilibrium is reached in systems throughout the brain. The intralaminar nuclei of the thalamus receive fibers from all parts of the neocortex, the brainstem, cerebellum and spinal chord.^xxx (See diagram of the mechanism of acting.)

In the transformation of the non-mammalian into the mammalian brain, therefore, we find all three subsystems required for the subjective animal behavior guidance system (sensory input, behavioral output, and goal selection systems). Each involves a distinct circuit through the thalamus and neocortex, which allows neurons in multiple 2-D arrays throughout the circuit to be coordinated and aligned with one another. That puts each subsystem on a higher level of neurological organization than the non-mammalian vertebrate brain. Moreover, in the sensory input and behavioral output circuits we find both subsystems required according to our functional diagram for the subjective animal system of representation with spatial imagination (that is, local images and memory in the sensory input system and behavior generator and body image in the behavioral output system).

As we have seen, such a complex system is possible, at least in chordates (with the nervous system set up in a separate neural tube), because the higher level of neurological organization can be generated by a couple of relatively simple, albeit radical, modifications in the non-mammalian vertebrate brain, and neurological development involves a contained form of reproductive causation that internalizes the spatial structure of the world as the detailed structural causes of spatial imagination. Since the subjective animal behavior guidance system is also functional, we infer by the nature of reproductive causation that this stage of animal evolution in inevitable.

In the next section, we will consider the empirical evidence of the subjective animal stage of evolution. Though empirical confirmation of necessary truths is not necessary, it is relevant, because empirical evidence can falsify the foundation of ontological philosophy.

That will leave one final conclusion to be drawn, about the unity of consciousness in mammals.

It is appropriate to think of the mammal as a subject, since its spatial imagination gives it an understanding the structure of space and the regularities about motion and interaction for which it is responsible as an ontological cause. By seeing the actual locations of objects against the background of what is possible by motion, the subject sees the world as a world of objects in space. Even its own body is seen as located in space alongside other objects. But the mammal is not just a subject. It is a conscious subject.

When combined with the explanation of the basic nature of consciousness (that is, phenomenal properties as intrinsic essential natures of bits of matter), the structure of the mammalian brain also explains the unity of subjective consciousness, that is, why all the sensory qualia appear to a single subject at one time. There is a phenomenal appearance to the world of object in space and the body by which the subject acts in that world. Nor do the objects that subjective animals experience as located in space appear merely as object in space, because they also feel desires of various kinds about them. We will return to the unity of consciousness after considering the empirical evidence about the gradual evolution of mammals.

The gradual evolution of mammals. Though mammals are named after their distinctive mammary glands, their neocortex is an equally distinctive trait, and as suggested in discussing the structure of the non-mammalian vertebrate brain, it comes from a reorganization of the thalamus that transfers responsibility for all three subfunctions of the animal behavior guidance system to the forebrain. Since the neocortex derives from the reptilian DVR, mammals could not evolve until reptiles had evolved.

This reorganization had be tried out soon after reptiles, however, rather than later, for it is such a radical random variation that only the most primitive reptiles could continue to function. By the time reptiles had acquired as much power as possible for animals of their kind, their DVR would have become so essential to so many different kinds of behavior that such a radical random variation would probably have been fatal.

This obstacle is most obvious in the avian brain, where the DVR/striatum is divided by well-defined laminas into many separate regions serving special functions, such as controlling pecking and generating bird songs. Each part of the telencephalon generates behavior separately, by its influence on the midbrain and hindbrain. It is not that the advantages of complete circuits through the forebrain are entirely overlooked in birds. It does occur, but in a more limited way. As we have seen, birds evolved a mammal-like memory; the "visual Wulst" is part of a mechanism that resembles the mammalian memory circuit.^xxxi But the avian brain lacks spatial imagination, because without a behavior generator that operates on a somatotopic representation of the body, it cannot acquire behavioral schemata from experience with the structure of space, but must rely on mechanisms supplied by the primary structure. Nor does avian memory include any sensory modalities beyond vision. It appears that the DVR-striatal circuit had become too complex by the time birds evolved for the DVR to migrate to the dorsal cortex and become a neocortex. Thus, birds have only a memory which is, at most, an advanced telesensory memory, that is, using a one-dimensional series of stimulus-response connections to get around in space as part of an instinctive routine for controlling specific conditions. But the visual Wulst is all birds need to record locomotor commands in relation to visual images and calculate directions and distances to unseen objects, for that enables them to find their way back to their nest, patrol at territory, and migrate with the seasons using visible landmarks.

Fossil evidence shows that mammals did evolve from primitive reptiles as our theory predicts. The last common ancestor of mammals and extant reptiles was 300 million years ago, about the time that reptiles first evolved. But there is still a problem with our explanation of mammalian evolution, which accidentalists often use to argue that mammals are not inherently superior, but merely different from, non-mammalian vertebrates: if mammals are more powerful, why were they dominated by dinosaurs for nearly 150 million years before the radiation of mammals? It seems that there would never have been a radiation of mammals, if it had not been for the impact of an asteroid. To answer this objection, we must consider the course of mammalian evolution.

Earth was dominated by mammal-like reptiles before dinosaurs evolved (about 225 million years ago). Mammal-like reptiles (therapsids) had tucked-in elbows and legs positioned more directly under their bodies, so they were better able to scamper over land than reptiles and probably fed on them. They used the energy, not only to stand upright, but also to supply a warm-blooded metabolism. Although some therapsids were as large as wolves, they were largely eclipsed by two-legged predatory dinosaurs about 225 million years ago.

But mammals continued to evolve during the age of dinosaurs. About 190 million years ago, mammal-like reptiles gave rise to a branch of primitive mammals (prototheria) which seem to have living descendants, the monotremes: the duckbilled platypus and the spiny anteater.

To judge by them, primitive mammals were warm-blooded and hairy. Although the platypus is still an egg-laying animals, it nurses its hatchlings and cares for its young, which is a radical innovation, considering that most reptiles have so little concern for their offspring that they sometimes eat their hatchlings when they come across them hungry. And monotremes have the mammalian neocortex (although it is not differentiated into as many areas and lacks the corpus callosum, the massive bundle of fibers that links the two hemispheres of neocortex in true mammals).

Later during the age of dinosaurs (about 135 million years ago), marsupials (metatheria) branched off from true mammals (eutheria), indicating that mammals had evolved all the basic traits that distinguish them from non-mammals during the reign of the dinosaurs, including live birth. But that did not enable mammals to replace dinosaurs in their energy-rich ecological niches, even though prototheria had about 55 million years and metatheria and eutheria had 70 million years to do so.

It seems, therefore, that what finally brought the age of dinosaurs to an end was not the inherently greater power of animals from a later stage of evolution, but an accident — the impact of a giant meteor or asteroid about 65 million years ago. The age of mammals might never have begun, if it depended only on the greater power of a higher level of part-whole complexity in the brain.

This accidentalist argument against the inherent superiority of mammals can, however, be answered when evolution is explained by reproductive causation. Incumbency in an ecological niche has an obvious advantage, and to deny that evolution is merely a matter of tracking changes in the environment is not to deny that catastrophic environmental change shakes out the natural kinds best suited for the more energy-rich ecological niches by forcing incumbent species from earlier stages to compete on a more equal footing with inherently more powerful kinds of living objects. This is the role of environmental change in the case of mammalian evolution. Indeed, it suggests that the question should be turned around. If mammals were not inherently superior, then how did they manage to displace dinosaurs when a catastrophic change did finally occur?

The mammalian nervous system evolved during the age of dinosaurs, and the more profound question is how mammals could evolve at all in competition with the incumbent dinosaurs. The answer seems to be that mammals occupied a more demanding ecological niche, where dinosaurs could not compete. And what made that possible was an animal system of representation with spatial imagination.

The first mammals were small, rodent-like animals that apparently foraged (for insects) at night, when dinosaurs could not see them or, perhaps, were immobilized by the cold. Sight was not their major telesensory modality, if we judge by the relative smallness of their eyes. Instead, they had long snouts and external ears, which suggests they had highly developed olfaction and hearing, both of which can be used just as well in the dark. Since all the telesensory modalities contribute in the same way to spatial memory in the subjective animal system of representation,^xxxii mammals could get around in the dark at least as well as reptiles do with light using only touch, hearing, and olfaction. Touch (including whiskers) would enable them to detect nearby objects, and using their map of the territory, they could get about well enough by keeping track of how far they move in each direction. Their spatial imagination would give them an experience of moving among salient objects in their territory much like the "virtual reality" generated by computers. Hearing (and olfaction) would tell them about objects at a distance, both their location and kind. And olfaction would enable them to recognize particular objects, confirming locations in their map. Thus, mammals could get around in their territory just as well when they could not see.

The subjective animal system of representation also explains parental behavior, including nursing, by which mammals are named. We have seen how the structural cause for various kinds of behavior, that is, the behavior schemata for setting up and using both local images and maps of the territory, are acquired from experience with the structure of space in moving around among objects in 3-D space, rather than from the biological behavior guidance system. Thus, mammalian young are simply not able to acquire energy in the ecological niches they inherit from their parents until they have matured enough to construct local images and link them together in their own maps of the relations of objects in space, that is, as a World Image. Just as birds must care for their offspring before they can fly and acquire energy for themselves, so mammals must care for their offspring until experience in locomotion enables them to develop a spatial imagination. Thus, mammillary glands (in monotremes) and live birth (in marsupials) are probably just an elaboration of the nurturing behavior required by the subjective animal system of representation (as indicated by the early evolution of the neocortex).

One hundred fifty million years is surely long enough to make the subjective animal system as effective as possible in representing the world as a world of objects in space, and so, when the impact of an asteroid caused clouds that changed the climate, destroying rain forests and rich vegetation over much of Earth, mammals were better able to adapt to the new conditions than dinosaurs.

As telesensory animals, dinosaurs had to rely on more or less complex fixed action patterns that enabled them to construct maps, acquire energy, and attain other goals in the previous, lush environment, and reproductive causation was the only way to adapt those complex instincts to radically new conditions.

Mammals, however, had the advantage of spatial imagination; when a desire was strong, they had the capacity to predict what would happen if they moved their bodies in space before they acted, so that "hypotheses die[d] in their stead." And with a behavior generator that operates on a body image to send separate motor commands to all parts of the body, mammals were able to generate new kinds of behavior by putting local motor commands together in new ways and, thus, could learn new kinds of behavior by trial and error within a single lifetime.

Hence, mammals had a distinct advantage when the environmental catastrophe put them on a more equal footing with dinosaurs. Dinosaurs were, of course, already much larger animals, and so it is not surprising that it took many generations before the mammalian population increase and the adaptation of their bodies to the new ecological niches deprived dinosaurs of their sources of energy.

Dinosaurs may have continued to exist for thousands of years after the impact of the asteroid, but that would not be long enough for them to evolve the new instincts needed to exclude mammals from their high energy ecological niches. Or to put it the other way, if there had been no mammals, dinosaurs would not have had to compete for energy, and they would probably have adapted to the new environment in the end.

Therefore, although the “radiation” of mammals was occasioned by the extinction of dinosaurs some 65 million years ago, the basic cause was not that dinosaurs were selectively wiped out by an asteroid, leaving mammals to inherit the earth. The asteroid merely changed all the sources of usable energy tapped by animals of both kinds so radically that mammals were able to replace dinosaurs in the new ecological niches because of the inherent superiority of the mammalian brain, with a neocortex, in which a spatial imagination made them better able to acquire usable energy.

It may still seem that the evolution of mammals is not inevitable, because evolution would not proceed through the whole series of possible stages if it were not for such catastrophic events shaking things up enough to make subsequent stages of inherently more powerful primary structures inevitable.

However, it is not an accident that radical changes occur in all the ecological niches at once. It is inevitable on planets like ours. For example, if asteroid bombardment is a result of perturbations in an Oort cloud of debris farther out from the star than where planets can form, as has been suggested, it would probably happen on any planet where life evolves at all. And there are other sources of asteroids. Thus, catastrophic events are normal on planets that orbit stars, and the dependence of evolution on them would not make the stages any less inevitable.

Furthermore, to assume that the overall course of evolution depends on occasional catastrophes is not to suppose that natural selection is caused, after all, by externally originating changes in the environment. What makes it seem that evolution is merely tracking externally caused changes in the environment is thinking of evolution as if only a single species were involved. But when evolution is explained by its ontological causes, we see that many species evolve during each stage of evolution, and from that broader perspective, we can see that the main effect of catastrophic changes in the overall course of evolution is to shake things up so that inherently more powerful organisms are not stymied by the accumulation of accidents. It makes evolutionary stages inevitable. Catastrophes cause mass extinction of species, and the “adaptations” that do take place are the increasing power by which the gradual evolution of inherently superior organisms taps usable energy in all parts of the environment, such as the radiation of mammals after the extinction of the dinosaurs.

The mammals’ higher level of neurological organization does, therefore, account for their gradual evolution, both before and after the catastrophe with which the Age of Mammals began some 65 million years ago. They could occupy more demanding ecological niches alongside dinosaurs before the catastrophic change, and then, once they could compete on a more equal footing, there was a bush-like radiations of mammals. After overcoming the dinosaur's advantage as incumbents in ecological niches, reproductive causation would adapt mammals to acquire free energy from all possible sources in all possible habitats, from jungles and forests to meadows and deserts, and from oceans and rivers to caves and polar ice caps. In short, from our ontological foundation, we can predict not only the revolutionary change with which the age of mammals began, but also the radiation of mammals. It eventually occurs on any planet where life evolves at all.

There is, however, a puzzle. If mammals are inherently more powerful, why didn’t they also displace the birds? Mammals can evolve the capacity to fly. Bats are proof of that. But bird continue to occupy almost all the other high-energy ecological niches open to flying animals.

Are birds incumbents in ecological niches that require a more severe environmental catastrophe before they can be displaced?

Or do ecological niches that depend on flying require only a one-dimensional visual memory for chains of stimulus-response connections that are imbedded in instinctive routines? Since bats fly at night and in caves, where birds usually cannot fly, are they merely taking advantage of their subjective animal system of representation to occupy an ecological niche that is not open to birds? That is, does a vision-based memory without spatial imagination make telesensory animals so powerful in ecological niches that require locomotion by flying that animals with a multi-modal memory and spatial imagination have no advantage — at least, none great enough to compensate for the greater costs of developing a nervous system with a higher level of part-whole complexity?

The unity of consciousness. In Properties, the nature of consciousness, that is, the existence of phenomenal properties, was explained by showing that material substances must have an intrinsic aspect to their essential natures. Spatiomaterialism implies that elementary bits of matter have intrinsic natures. That is enough to explain simple sensory qualia. But that is not a full explanation of the nature of consciousness, because it does not show that intrinsic natures can explain the kinds of phenomenal properties we have (as we noted when explaining the nature of the necessary connection that solves the contemporary naturalists problem of mind in Properties: Ontological explanation of the necessary connection between physical and phenomenal properties).

What reflection (or introspection) reveals are complex phenomenal properties with qualia of many different kinds all appearing to the subject at once. But spatiomaterialism entails a kind of panpsychism, in which only the most elementary bits of matter must have intrinsic natures. Since the intrinsic natures of elemental bits of matter are presumably only proto-phenomenal properties, it remains to explain what Nagel calls the “unity of consciousness.”

But how can the intrinsic natures of the most elementary physical objects account for complex phenomenal properties? It cannot come from how simpler physical objects are related spatially as parts of more complex physical objects, for there is no reason to believe that a composite physical object, like the brain, will have an intrinsic nature as a whole. The parts of the brain are outside one another in space, and the unity of the whole brain depends on the extrinsic natures of the parts, since what holds the parts together and enables them to interact are the forces that they exert on one another. Thus, it may seem that spatiomaterialism cannot explain why the subject as a whole has phenomenal properties in which qualia are combined in such rich appearances as those that occur in perception.

The nature of complex phenomenal properties. There is one way that spatiomaterialism can explain phenomenal properties (and only one way, as far as I can see). In order to see how it works, we must take into account both the basic nature of matter and the structure of the mammalian brain.

The nature of matter. Spatiomaterialism takes “matter” to refer to all the forms of mass and energy whose quantities are counted in the principle of the conservation of mass and energy, including all the kinds of particular entities to which the basic laws of physics refer. Quantum field theory distinguishes two different kinds of basic particles, fermions and bosons. They have opposite natures in a relevant way.

Fermions and bosons have opposite relationships to other particles of the same kind.

Particles such as electrons, quarks, and nucleons are fermions. With “½ spin” (or a multiple of it), they exclude other objects of the same kind from occupying the same location or quantum state (except for one other particle with the opposite orientation of spin).

Photons, with a spin of 1, are the prime example of bosons (though bosons can also have spins of 0 or 2). Bosons do not exclude one another from occupying the same quantum states, and so there is no limit to the number of bosons of any kind that can have the same location.

Fermions and bosons have opposite relationships to space.

Fermions (with mass) are most like ordinary physical objects, for they are point-like particles (or spatial complexes of them) which are able to be at rest is space.

Photons are interacting electric and magnetic forces, and by contrast to fermions, they seem to be spread out in space, for even though they exist only as whole (quantum) units, they move through space at the velocity of light. (A boson-like nature is also found in the electric forces by which fermions interact with one another, but as we have seen this form of matter is spread out as a field and the way it coincides with space means that its quantity is included in the total rest masses of the objects exerting the forces.)

According to spatiomaterialism, all the simplest bits of matter mentioned by physics must have intrinsic natures. But since bits of matter can occupy more than just a single point in space, there is no reason to deny that their intrinsic natures can have spatial structures. That suggests that, since photons seem to be units spread out in space, they could have intrinsic natures with complex spatial structures, even if fermions do not.

The basic nature of photons opens up, therefore, the possibility of an explanation of complex phenomenal properties by intrinsic natures. But we are still far from seeing how it works.

To be sure, the photon-like nature of the electromagnetic forces binding electrons to nuclei in atoms and atoms to one another in molecules may also give each of them an intrinsic nature as a composite whole. But their intrinsic natures extend only as far as the objects they bind, and since that is not far enough to include whole brains, their intrinsic natures can hardly account for phenomenal properties. To see how it is possible, we must consider the structure of the brain.

The structure of the mammalian brain. The basic structure of the mammalian forebrain involves a massive projection of neurons from the thalamus to all parts of the neocortex (and back), and as we have seen, the brain’s main functions are all served by its massively parallel information processing. Different nuclei in the thalamus project to distinct regions of neocortex, and there are three complete circuits from the neocortex through other structures back to the thalamus and neocortex. Information is being processed within those circuits in two-dimensional arrays of neurons (as shown by association fibers that connect them topographically). Many such 2-D arrays in the posterior neocortex are clearly processing sensory information about the same objects in space at the same time, and many other 2-D arrays in the anterior neocortex are processing both sensory input from and motor output to the body at the same time. Finally, a 40-75 hertz pattern of firing set up by the thalamus apparently synchronizes activity in all areas of the neocortex, integrating the three complete circuits.

Crick and Koch (1990) defend the hypothesis that the 40-75 hertz synchronization of the firing of thalamic neurons to the neocortex is the foundation of consciousness. But they do not explain how it gives rise to phenomenal properties. Given the spatiomaterialist explanation of intrinsic natures, however, phenomenal properties could be explained as the intrinsic natures of the electromagnetic waves set up by the synchronized firing of neurons throughout the thalamic projection to the neocortex.

Electromagnetic waves are, of course, photons, one of the basic forms of matter contained by space, and since they are generated by the acceleration of charged particles, they are clearly being generated by brain activity. A neuron carries signals from one place to another by an “action potential” which propagates along its axon as ions of one kind at each successive point rush into the neuron and then ions of another kind flow back out. The acceleration of such ions makes the synchronized firing of thalamic neurons act like an antenna, generating a complex electromagnetic wave.

Since electromagnetic waves, being composed of elemental photons, are a form of matter whose spread-out nature could give their intrinsic nature a spatial structure, there is an elemental bit of matter generated by active brains whose intrinsic nature could have enough spatial structure to account for complex phenomenal properties. It is the electromagnetic energy being given off as a series of complex photons by a human brain that is not asleep.

This is all the more plausible when we consider that the brain, despite making up only a few percent of body weight, accounts for nearly 20% of the body’s total energy consumption.

In order to be sure that the intrinsic nature of the energy being given off by the brain accounts for phenomenal properties, more would have to be known about the complex geometrical structure of the photons generated by the synchronized firing of neurons in the thalamic projection to the neocortex. Indeed, it is likely that much more remains to be discovered about the basic nature of light than physicists suppose. But that is beyond the scope of this argument. But for our purposes, it is enough to see how this ontological explanation of the nature of properties, this ontological explanation of the truth of physics, and this ontological explanation of the structure of the subjective animal system of representation combine to provide an explanation of the kinds of phenomenal properties that beings like us have.

Complex phenomenal properties. To make it plausible that what is relevant is the energy being given off by the thalamic projection to the neocortex, let me suggest how it would explain what Nagel called the “unity of consciousness.”

The unity of consciousness can be seen in perception, for at any moment, many particular qualia from several sensory modalities all appear to be located in and around one’s body in what can only be called phenomenal space. Objects with colored surfaces appear to have locations around the body, and they often make noises that seem to come from their locations. Color and tactile qualia also seem to be located in the body, and as it moves, one can feel objects at certain locations in space outside the body. The spatial coherence of the perceptual appearance is so complete that many philosophers who are otherwise critical realists still assume that the space in which sensory qualia appear to be located is the same space in which the objects (and body) they represent actually exist, that is, the the qualia are somehow projected outside the brain. But since spatial aspects of perception are just as much part of phenomenal properties as the sensory qualia themselves, we must distinguish phenomenal from real space.

There are at least three reasons to believe that complex phenomenal properties like these can be explained by the intrinsic natures of the photons generated by the thalamic projection to the cortex.

First, as the anatomy of the brain suggests, all the information processing of sensory input leading to motor output that is going on in the brain is registered in the firing of neurons in the thalamic projection to the neocortex and, thus, in the electromagnetic waves it generates.

There are three way in which the projection from the thalamus to the neocortex projects back to the thalamus, completing a circuit. All areas of neocortex have association fibers that project to the temporal lobe near the hippocampus and thereby connect (via the fornix) with the anterior nucleus, which projects back to the cingulate gyrus of the neocortex. All areas of the neocortex also project to the corpus striatum and thereby connect through the ventral anterior and ventral lateral thalamic nuclei back to the frontal neocortex. Also located in the temporal lobe is the amygdala which connects by way of the dorsomedian nucleus of the thalamus back to the frontal regions of the neocortex. The first circuit clearly mediates the formation of long term memory; the second generates behavior in relation to objects in space; and the third attaches desires to objects by arousing disposition to behave toward them in certain ways. Thus, the thalamo-cortical projection seems to mediate all the main brain functions.

But since the neocortex is one of the mechanisms involved in all three complete circuits which realize the subsystems of the subjective animal behavior guidance system in mammals, its neurons (including association fibers between 2-D regions of neocortex) may also contribute to the photons whose intrinsic nature constitutes phenomenal properties.

Second, it seems possible to explain the spatial coherence of complex phenomenal properties, at least, in principle. It is likely that simple sensory qualia are parts of the electromagnetic wave generated by thalamic neurons projecting sensory input to primary sensory areas of neocortex, for when they fire, they fire at an unusually high rate. The appearance of green at a certain location in the visual field, for example, is presumably due to the rapid firing of certain neurons in the 2-D array projecting from the lateral geniculate body of the thalamus to the visual (striate) cortex.

Given how colors vary with different combinations of the intensity of opponent colors (red-green, blue-yellow, and black-white), the relevant wave patterns presumably depend on the combination of neurons projecting to each region of the visual cortex that originate at different lamina of the lateral geniculate body and fire at different synchronized rates.

Since all the 2-D arrays processing visual input in the neocortex are connected to one another topographically by association fibers, the neurons in each that represent the same parts of an object’s visual appearance are presumably synchronized throughout the neocortex. That ties higher-level processing to the corresponding neurons responsible for sensory qualia and integrates all their effects on the electromagnetic wave, so that its spatial structure could contain all the information the brain uses for guiding behavior.

The same is true of the various 2-D arrays representing the body, and given how those body representations are connected with visual and other sensory 2-D arrays, it is not implausible to suppose that the result is a series of photons generated by the entire thalamo-cortical projection whose intrinsic natures are spatially coherent. That could be why sensory qualia seem to have locations in phenomenal space.

The fainter qualia of all sensory modalities that occur in memory and imagination could likewise be explained as due to centrally-generated firings of neurons that otherwise occur only in later stages of the process of sensory analysis.

Finally, locating the phenomenal property in nature as the intrinsic nature of the electromagnetic wave generated by the thalamic projection to the neocortex would explain the phenomenon of blindsight. When the projection from the thalamus to the visual cortex is damaged and subjects claim not to have any visual experience, they are still able to answer questions about the locations and shapes of objects and to take them into account in their behavior. The lack of visual qualia is what would be expected on this theory, since what is missing is the relevant thalamo-cortical projection. And the residual visual discrimination could be explained by the visual processing still going on outside the forebrain in the superior colliculus (the midbrain nucleus that was responsible for using visual input to guide behavior in reptiles) and its limited projection to a region of the thalamus (the pulvinar) that projects to secondary areas of the visual neocortex.

Ontological philosophy offers, therefore, a plausible explanation of the unity of consciousness. The physical properties of the photons generated by the brain suggest that they are a form of matter whose intrinsic natures could be the complex phenomenal properties we have. What makes it possible to solve the explanatory problem that Nagel finds in panpsychism is the recognition that space is a substance. Coinciding with space explains not only why bits of matter have spatial relations to one another, but also how they can coincide with whole regions of space. Thus, it shows how their intrinsic natures could have complex spatial structures, and that makes it possible to see how photons can have a spatial structure that depends on activity throughout the brain, accounting for the complex structure of the phenomenal properties that we are calling "consciousness."

An attractive feature of this explanation is that it suggests a research project. Complex phenomenal properties might be explained in detail by working out precisely the geometry of the electromagnetic waves generated by ions being accelerated in and out of cylindrical axons of certain neurons in each of many 2-D arrays of the massive, basically parallel projection from the thalamus to the neocortex as they fire simultaneously 40-75 time each second.

Furthermore, if the synchronization of firing cycles throughout the thalamus is required for the coherence of the complex phenomenal property, it can settle a question about the unity of consciousness in split-brain patients. In split-brain patients, the massive corpus callosum which connects the two hemispheres of the brain is cut (usually in order to prevent epileptic seizures). Whether they have one or two minds, that is, one or two unified appearances made of sensory qualia in phenomena space, would depend on whether their thalamic nuclei are still synchronizing the firings of neurons in both hemispheres. That is something that could be determined empirically.

Implications. Even without carrying out those research projects, however, this explanation of phenomenal properties, if true, has consequences that are relevant to the positions mentioned in the discussion of consciousness in Properties.

Epiphenomenalism. Thomas Huxley likened epiphenomenal properties to the whistle or steam giving off by a steam locomotive, because they have no causal role in propelling the train. If we take “epiphenomenal” to mean being an effect of physical properties without having any effects in turn on physical properties, the spatiomaterialist explanation implies that phenomenal properties are epiphenomenal in two different ways.

First, as we have seen, phenomenal properties are epiphenomenal relative to physical properties as such, because they are kinds of intrinsic natures that are caused to exist as a result of extrinsic natures of the bits of matter involved. That is, the spatial structures of the photons that account for the complexity of the relevant phenomenal properties are also aspects of the extrinsic natures of those bits of matter, because those spatial structures can in principle, be explained by physics.

Second, since the relevant bits of matter are the electromagnetic waves, they are just a form of energy being dissipated by the brain as a by-product of its activity, and so those bits of matter themselves are epiphenomenal relative to the physical properties of the brain itself. Those photons are effects of the brain’s activity that do not, in turn, affect its states. (What happens in the brain is caused by the synapses made by the neurons that fire, not by the photons generated by their action potentials.)

Thus, phenomenal properties depend on two “causal” connections, the efficient cause by which the brain activity causes electromagnetic waves, and the ontological cause linking the extrinsic natures of the electromagnetic waves to their intrinsic natures.

Robot consciousness. Given that phenomenal properties are the intrinsic natures of the brains’ electromagnetic waves, it is not very likely that robots whose behavior is guided by computers made of silicon chips will be conscious in the way we are. Though they will also generate electromagnetic waves and will, therefore, have some intrinsic nature or other, it is unlikely that their phenomenal properties will be anything like our own.

Their information processing is basically serial, rather than parallel, and since silicon chips have, in any case, a completely different geometry from brains, the rising and falling electric and magnetic forces in the “wires” of silicon chips will generate photons with a completely different geometry in space and time.

Nor can such robots experience sensory qualia as located in space, if what is responsible for the unity of consciousness is, as suggested above, the synchronized processing of representations of the same objects in different, interconnected 2-D arrays of neurons projecting to the neocortex.

Ontological philosophy also implies, therefore, that Chalmers (1996, Chapter 7) was mistaken to believe that phenomenal properties are caused by functional, rather than by physical properties. His argument was the implausibility of qualia slowly “fading” out as parts of the brain were replaced by functionally equivalent silicon circuits, and the implausibility of color qualia “dancing” from one kind to another (or to none at all) as the processing of part of the visual array was switched between brain mechanisms and silicon chips. Implausible though it may seem to Chalmers, that is what must happen, if phenomenal properties are the intrinsic natures of electromagnetic waves generated by the processing. But at this point, his fading qualia and dancing qualia arguments show, not the implausibility of phenomenal properties being caused by physical properties, but rather the perils of giving up the empirical method (as in empirical ontology) in favor of philosophical arguments from plausibility (where functions and other properties seem more basic than substances).

Knowledge of phenomenal properties. Ontological philosophy makes consciousness a part of natural science without abandoning the empirical method in favor of the traditional epistemological approach to philosophy. But since it implies that phenomenal properties are epiphenomenal, they have no effects on what happens in the natural world, and thus it may seem that phenomenal properties cannot be known even privately. How can subjects know about their phenomenal properties, if those properties are never causes of what they say about them?

That phenomenological properties do cause beliefs about them is apparently what Descartes assumed in arguing, "I think, therefore I am." In order for thinking to show the subject that he exists, the subject must know that he is thinking when he is thinking, and Descartes seems to take it for granted that the subject knows that he is thinking because the appearance of the ideas in the mind makes the subject aware of what is happening in his mind. (That is the "illusion involved in reflection" that Descartes still does not see through after he sees through the "illusion involved in perception" and becomes a critical realist.)

Nor would this problem arise if phenomenal properties played the kind of causal role mediating between sensory input and behavioral output that Searle (1992, 1995, and 1997) ascribes to pain, that is, being an effect of, say, a pinch, which in turn causes one to say “Ouch!” In that case, phenomenal properties would be effects of sensory input, and they would be the causes of reports about them. But causal emergentism of that sort is incompatible with spatiomaterialism.

Given this explanation of the mammalian brain and consciousness, however, it is not necessary for phenomenal properties to be efficient causes of behavior in order for them to be private objects of knowledge.

First, to see how we can know that we have phenomenal properties, we need only recognize that such knowledge comes from (and arose historically in modern philosophy from) accepting critical realism, that is, distinguishing phenomenal properties from physical properties. It is like something to be a human being, as we have seen, because the functioning brain involves a bit of matter whose intrinsic nature registers the activity of the entire brain. We assume, as naive realists, that the world as it appears to us in perception is the real world, with qualia located in objects that are assumed to exist independently of us in space. But when we recognize that perception is a physical process in which the objects stimulate our sensory organs, thereby giving rise to brain states representing them, we can come to see that our sensory qualia are parts of us, as the subject who is perceiving, not parts of the independently existing objects. And if we follow this argument to its conclusion, we also come to recognize that the space in which sensory qualia seem to be located is merely phenomenal and, thus, distinct from the space in which the physical objects actually exist. Critical realism about perception makes it clear that objects with physical properties in real space exist somehow “beyond” the complex phenomenal properties we have, so that we discover that we have phenomenal properties by recognizing that physical properties do not appear to us at all, except indirectly through phenomenal properties.

These spatial configurations of sensory qualia are not the only complex phenomenal properties we have, but they are an important variety, and the failure to give up naive realism about space in favor of critical realism about space is the source of much confusion about the nature of consciousness.

Thus, second, there is no problem explaining how it is possible for subjects to pick out particular qualia included in the structures of their phenomenal properties. The phenomenal properties involved in perception are configurations of sensory qualia in phenomenal space, and particular qualia can be picked out in the same way as the objects in real space that they represent, for once we recognize the difference between physical and phenomenal properties, it is one and the same brain capacity being understood in two different ways. We can take our reference to the green apple on the table to be a reference either to the physical object in real space or to a part of the appearance that the world has to us as we perceive the world.

Finally, there is no problem explaining how we know about the kinds of particular sensory qualia that are picked out that way, for once again, it is just to make the same discrimination that we make in describing the properties of physical objects in real space together with the recognition that there is a difference between physical and phenomenal properties. When I call the cup green, I am ordinarily understood as referring to a physical property of the cup (its disposition to cause a certain kind of experience in us). But when I distinguish the phenomenal property from the physical property, I can also identify the kind of qualia representing the physical property. And there is a kind of incorrigibility to the belief about the kind of particular sensory qualia that does not hold for the physical property, for what is meant by the kind of sensory qualia is how it appears to the subject and that is something that is known ostensively in the phenomenal property.

Ontological philosophy, therefore, makes a natural science of consciousness possible. Though we know about our own phenomenal properties in a unique and private way, we can know that others have them. If other brains generate the same kinds of electromagnetic waves as ours, we can know from what experience is like for us, what it is like for them.

But traditional epistemological philosophy will not survive this change, for it makes even the starting point of modern philosophers, like Descartes, part of the essential nature of a world that is explained ontologically. That is, what will make a natural science of consciousness possible is that there will no longer be any difference between empirical science and philosophy when philosophy takes empirical ontology as its foundation (and science recognizes ontology as a more basic branch than physics). But this is to get ahead of ourselves, for that is how ontological philosophy completes the tenth stage of evolution.

7 Manipulative stage. Having traced the evolution of the animal system of representation from somatosensory through subjective animals with spatial imagination, the manipulative animal system of representation can be predicted, in principle, by the function of structural imagination. Just as spatial imagination gave the mammal an intuitive understanding of spatial causation, structural imagination gives primates an intuitive understanding of structural causation. That is, subjective animals were more powerful than telesensory animals because they could understand how the structure of space imposes regularities on the object’s change of location, and in a similar way, manipulative animals are more powerful than subjective animals because they can understand how the geometrical structures of material objects in space imposes regularities on their interactions. Though there must be some new kind of behavior for it to guide, structural imagination makes it possible to guide such behavior in using structural causes to control relevant conditions. It would be such a basic addition to the power of animal behavior to act on other objects in space that it could begin a stage

In order to predict a stage of evolution during which manipulative animals change in the direction of maximum power in using structural causes, however, it must be possible for subjective animals to try out a random variation that gives animals structural imagination. The functional description of the structures required for structural imagination shows why such a “manipulative animal system of representation” would require a higher level of neurological organization than subjective animals. Thus, only its possibility remains to be shown, in order to infer its inevitability as a necessary truth of ontological philosophy. But the higher level of neurological complexity required for structural imagination does not require such a radical change in brain structure that it is problematic. Moreover, what it does require explains all the ways that actual primate brains are different from mammalian brains.

After giving a functional description of the manipulative animal system of representation, I will describe the structures in the primate brain that realize it and, finally, confirm that it causes a stage of evolution by considering the empirical evidence for a radiation of higher primates.

The function of the manipulative level of neurological organization. The reason that a less radical random variation is needed to try out the manipulative level of neurological organization is that it happens in animals that already have imagination. It is just a higher level of part-whole complexity in the faculty of imagination.

Subjective animals have a faculty of spatial imagination that enables them to understand the structure of space. As we have seen, it comes from a memory that can link local images in sequences as a map of the territory and a behavior generator that generates covert locomotion that can call them up. This gives them subjective animals capacity to anticipate the consequences of locomotion, and motion generally, on the relations of objects in space. It is a conception of space, for it gives the subjective animal an understanding of spatial causation. They can perceive objects as having locations in space. It even enables them to see their own bodies as objects alongside other objects in space, and so the world in which subjective animals act is seen as singular and whole.

Besides the effects of motion on spatial relations, however, there is another spatial (and spatio-temporal) aspect of the world that is nearly as basic, which subjective animals cannot understand. That is structural causation, or the effects of geometrical structures on the interactions of objects that have them. Though mammals can guide locomotion in relation to large geometrical structures in their territory, they merely inhabit such structures and do not see them as the structures of material objects. Mammals have no need to understand structural causation, for they lack the ability to generate animal behavior of a kind that would use structural causes to control relevant conditions, that is, the capacity to manipulate material objects.

Structural imagination. What would make mammals more powerful, therefore, is an ability to manipulate material objects that is guided by an understanding of the consequences of manipulating them on how their geometrical structures appear, how the objects interact, and how their structures change. Understanding requires a faculty of imagination, but since mammals already have one form of imagination, the addition of another kind of behavior and another way recording images in memory is all that is required for what I will call “structural imagination.” It would enable manipulative mammals, for example, to see that round pegs won’t fit in square holes and that cups have to be oriented in a certain direction in order to contain water. More generally, it would enable them to see, in the geometrical structures of material objects, the structural global regularities they would cause, and with the capacity to manipulate objects, they would be able to use their geometrical structures as machines, or tools, in attaining their goals.

A faculty of imagination enables the animal subject to see the actual against the background of what is possible (where “the possible” is basically various sets of sequences of images over time representing the kinds of events that can occur). In the case of manipulative animals, that is to see the actual geometrical structures of objects in the local scene against the background of what is possible by manipulating them.

If its mechanisms paralleled spatial imagination in subjective animals, what is possible by manipulation could be presented to the animal subject (via the projection of the local image to the caudate nucleus) as sequences of images along with perception (or the images derived from current sensory input).

Using the same basic memory system for recording memory groups in sequences (the cingulate gyrus), the detailed structure of the brain mechanisms for generating such sequences of images could be learned by experience. We have seen how the faculty of imagination can contain a form of reproductive causation in which behavior schemata evolve by reinforcement selection. The detailed brain mechanisms for structural imagination can be internalized from the world itself, because that is where structural causes actually generate global regularities, and those regularities are evident in now sensory input depends on manipulative behavior.

Since covert behavior would call up images from memory, thought about geometrical structures would involve appearances to the animal. Given our ontological explanation of the nature of consciousness, those appearances would be the kinds of ideas of imagination and memory to which the modern philosophers were referring. In manipulative animals, therefore, the representation of geometrical structures would be explicit.

None of these consequences of behavior is even conceivable by subjective animals, because the geometrical structures of objects are merely implicit in their local images (the combined telesensory images of objects located in the current scene). When the subjective animal focuses on an object, its location in space is represented explicitly, because its telesensory effects are registered along with other telesensory images as parts of a local image (according to input from the bodily condition), and that image contains information that can guide locomotion in relation to objects located in the local scene. The local image is the perceptual appearance of the local scene to the subjective animal, and it is conscious perception, because it has a phenomenal appearance.

But even though the object’s geometrical structure may correspond to a structure in the local image, or telesensory image in the complex idea representing the local scene, its geometrical structure is not represented as a geometrical structure, because the object’s geometrical structure is not used to guide manipulation in relation to it, but, at most, to identify the object or to recognize its kind. The geometrical structure may enable the mammal to see that it is an object of some kind that is located in space. But the mammal does not see it as having a kind of shape that can be changed or used in some way. It is as if subjective animals moved around in a world of shapeless (yet identifiable) objects with locations in space, and with the evolution of structural imagination, those objects acquired shapes that could be used as means in attaining animal goals.

The goals pursued by manipulative animals would be somewhat different from goals of subjective animals. Goals would be selected in the same way, by attaching desires to objects, where desires are basically dispositions to behave in a certain way toward an object. But manipulative animals would have new ways of behaving. For example, apes can pick gnats from one another’s fur and build beds, while cats can only lick themselves (or their kittens) curl up somewhere comfortable. New desires would evolve, because with structural imagination, manipulative animals would be controlling relevant conditions that were out of reach for subjective animals.

In short, whereas subjective animals have a conception of space, manipulative animals would have a conception of geometrical structures in space. And whereas subjective animals perceive objects as being located in space, manipulative animals would perceive objects in space as having geometrical structures.

The various functions and sub-functions of the manipulative animal system of representation are depicted in the accompanying diagram of the manipulative animal behavior guidance system. Though neural mechanisms serving the function of selecting the kind of behavior are essential to the animal behavior guidance system, only the mechanisms serving the sensory input and behavioral output sub-functions are involved in the animal system of representation (the parts with the gray background). The diagram of the subjective animal behavior guidance system is also included here, because the contrast brings out what kind of higher level of neurological organization is required by the manipulative animal system of representation.

The functions of the systems making up the subjective animal behavior guidance system will be assumed, and only the additional systems required to supplement spatial imagination with the capacity to understand structural causation will be described. (The new neural mechanisms required to serve these new functions are identified below in the section, which uses the structure of the primate brain to show the possibility of the manipulative level of neurological organization.)

The brown squares represent the sensory input and behavioral output systems, and the black lines represent their basic connections to one another and the body (including telesensory input, somatosensory input, input about the current bodily condition, their combination as the perception of the object, and how that is responsible for overt behavior when some kind of behavior is selected). They are the basic structure of the telesensory animal system of representation. They are all depicted in the subjective animal behavior guidance system, but for simplicity in the manipulative animal behavior guidance system, the internal connections between the sensory input and behavioral output system (perception and input about the current bodily condition) are suppressed.

The red lines and red circles in the sensory input system and behavioral output system are what is added to the brain to give the subjective animal spatial imagination. Their complete circuits indicate the higher level of neurological organization in subjective animals (though as we have seen, the behavior generator is actually another complete circuit in itself, which is not represented in these diagrams).

The lavender lines and circles in the local image and body image of the subjective animal system of representation only suggest the kind of higher level of neurological organization required to give manipulative animals structural imagination, because there are actually four sets of new sub-systems, one for each hand and one for the object each hand can manipulate (which are not all represented for the sake of simplicity). The lavender lines represent the causal connections between the new sub-systems by which they function as the manipulative animal’s structural imagination.

Behavioral output system. Overt behavior for the whole body is caused by motor commands from the body image, as in other subjective animals. Those commands are issued by the behavior generator for the whole body using one of its behavior schemata. The behavior of hands in manipulative animals is caused in the same way, but within the context of the body. Hence, the behavioral output system for the hands is depicted as being located within the body image (though it is just a distinct part of the complete circuit through the frontal neocortex, corpus striatum and ventral thalamus for the whole body).

Overt manipulation is caused by motor output to muscles in each of the hands (and limbs) from each of the hand images, and the motor commands are generated by behavior generators for the hands using their behavioral schemata for manipulation. But the entire behavioral output system for the hands is depicted as being part of the body image, because, functionally, manipulation is a kind of behavior that is generated in just certain parts of the body.

Both are behavioral output systems, each with its own behavioral schemata, and thus, they are basically independent structural causes of behavior. In other words, there is a part-whole relationship between the behavioral output systems for the hands and for the body that corresponds to the part-whole relationship between the hands and body themselves. The behavior of the body as a whole is the larger context in which manipulative behavior is generated, as if manipulative behavior were simply appended to the behavior of the whole body. But they are distinct circuits, which can operate independently (and as we shall see in the linguistic brain, body and hands can both be operated by higher level linguistic schemata as if they were on a par).

The behavioral output system for the hand is labeled “hand image” because motor output to the hands is organized somatotopically as representations of the hands. The hand images are just parts of the body image, for the body image is organized somatotopically and includes the hands. And just as the body image receives somatosensory input from all parts of the body, the hand images receive somatosensory input from all parts of the hands.

But since tactile input, which is a kind of somatosensory input to the hands, is used to perceive the geometrical structures (and locations) of objects in the local scene, the diagram also represents tactile images as sensory input to the object image. (Thus, it might be called “exteroception,” to distinguish it from proprioception and interoception.)

The behavior generator for each hand contains schemata for all the various ways that that hand can manipulate objects, and depending on input from the goal selection system, the behavior generator uses one of its manipulative schemata together with the perception of the object in the local scene (that is, the object image, or the input from the sensory input system) to generate precise motor commands that are adapted to the geometrical structure of the object. Thus, hand-eye coordination is possible.

The behavior generator itself for both the body and the hands is also actually a complete circuit (through the ventral anterior nucleus of the thalamus, the frontal neocortex, and the corpus striatum, though it is not represented in the functional diagram). The behavioral schemata are structures recorded in the frontal neocortex, but it is a different region of the neocortex from the body image and hand images from which motor commands are issued (that is, the motor area).

The behavior generator can, with the appropriate behavioral schemata, generate a wide variety of manipulations. Since motor output sends commands separately to each part of each hand, they can be combined in many different ways. And manipulative schemata may involve many steps, because the behavior generator for each hand has feedback from the motor output to its hands by which the completion of one motor command can trigger the next in a sequence, generating temporally complex patterns of manipulation.

Sensory input system. As in subjective animals, the manipulative animal’s local image is constructed from the telesensory input of objects in the local scene, using input from the bodily condition to register telesensory images according to the stance of the body, head, eyes and ears that controls them in the local scene. But there is a new level of part-whole complexity in the local image, because telesensory (and tactile) images from objects are also registered as parts of an “object image” according to input about the bodily condition indicating the current motor commands and sensory input to the hands.

What makes an object image possible is that the local image also contains a new memory system by which telesensory and tactile images of objects can be recorded in sequences according to overtly generated manipulation and by which those images can be recalled in sequences according to covertly generated manipulation. The entire sensory input system for objects, both the object image and its memory, are contained within the local image, because, functionally, the object image is framed by the local image. It must be in order to represent effects of the geometrical structures of objects, because they occur within the local scene.

The object image functions more like the subjective animal’s entire map of local images than like their local image, because structural imagination gives the object image a meaning that resembles the meaning that spatial imagination gives to the local image.

As we have seen, the subjective animal’s capacity to see the telesensory images combined in the local image as spatial relations between objects that can change as they move comes from spatial imagination and its capacity to call up sequences of local images by covert locomotion. It gives the local image an “outside” relationship to other local images, and that makes the spatial relations among objects represented within the local image meaningful in a new way, because their locations can be seen as places where the animal might go and turn, calling up a new local image.

With the evolution of structural imagination, the local image has a comparable relationship to object images, except that object images are “inside” the local image, rather than “outside.” The object image is made up of sequences of telesensory and tactile images, representing the consequences of manipulation. But as they change, the local image remains the same (except for those changes). When a rock is rotated, for example, one side after another comes into view, but the background remains the same. However, the changes in the rock do not just happen, but are caused to happen by turning it in a certain way, and thus, the telesensory and tactile images that are part of an object image are meaningful. The geometrical structures that appear to the manipulative animal in those images have a meaning that comes from understanding geometrical structures in terms of the consequences of manipulating them, in much the same way as the meaning of the spatial relations among objects in the local scene comes from understanding them in terms of the consequences of locomotion and turning in relation to the objects. The manipulative animal can see the geometrical structure of the object as something that would change in a certain way, if it were rotated or twisted appropriately, just as the subjective animal can see the spatial relations among objects in the local scene as some that would change in a certain way, if some object were to move appropriately.

In other words, the object image and the territorial map have opposite relations to the local image and the telesensory and tactile images of which it is composed. The object image involves sequences of telesensory and tactile images within the local image, whereas the territorial map involves sequences of local images themselves, that is, outside the given local image.

In both cases, sequences of images are recorded in memory in conjunction with the kind of behavior being generated overtly at the time, and so they can be called up in the same order when behavior of the same kind is generated covertly. The difference is that the behavior that is relevant to changes in object images is manipulation, whereas the behavior that is relevant to changes in the local images is locomotion (and turning).

This parallel between spatio-temporal and structural imagination means that memory can function in basically the same way in both cases. In both cases, there must be a system that can record images in sequences. It must be able to record them according to the kind of overt behavior being generated at the time the images are received. And it must be able to recall images from memory according to covert forms of such behavior as labels, so that they appear as imagination to the subject. The same system that serves these functions in spatial imagination can be used for structural imagination, if (1) manipulative animals have a new form of behavior and (2) the images called up from memory can be handled somehow independently of the local image in which they occur.

(1) The foregoing description of the behavior generator for the hands explains how manipulative animals can have a new form of behavior. It comes from having hands as four new parts of the animal body. Thus, in addition to locomotion, turning, and the orientation of the body, head, eyes, etc., the manipulative animal has ways of behaving that depends on the hands and how the arms put the hands in certain locations in the local scene.

There are many different ways of manipulating objects. Objects can be turned, for example, in three independent ways in three dimensional space. The fingers can trace their outlines in different ways. And there are various ways of acting on objects to change their shape, as in folding paper.

Assuming that overt and covert behavior have the same kinds of connections to the memory system (projections to the anterior cingulate gyrus and its projection in turn to the posterior cingulate gyrus), each kind of manipulation could call up a different sequence of sensory images.

(2) However, since the memory system is already being used for spatial imagination, the new memory system must be able to have a different kind effect on the local image than locomotion and turning. In order to serve its function, instead of calling up new local images, it must be able to call up new telesensory (and tactile) images within a given local image. That is what is labeled as the “object image” within the local image of the functional diagram.

Though at any moment, the object may be just one of the telesensory images that are combined as the local image representing the current local scene, the object image is different, because it can be changed by covert manipulation independently of the rest local image, at least in imagination. That is the object image’s connection to the memory system within the local image in the functional diagram.

The world appears differently to animals with structural imagination. Not only do they see themselves as a body located in a local scene along with other object with spatial relations to one another that can be changed by locomotion, but they also see the objects in the local scene as having structures.

As the manipulative animal plays with an object, say turning it, it receives a series of telesensory and tactile images, and sensory images are registered according to what its hands are doing to it. This can record an object image for that particular object in memory. Thereafter, even though only one aspect of the object may be causing sensory input at the moment, the object image can represent other aspects of the object as well, for images of the other sides can be called up from memory. Thus, manipulation involving the backside, for example, can be rehearsed in imagination before it is generated overtly. The manipulative animal perceives the object as having a certain back side. Or objects with moving parts, such as a box with a lid, can be imagined to have configurations that are not seen.

But the capacity to record and recall sensory images according to manipulation is not just a memory for particular objects, any more than the capacity to record and recall local images according to locomotion is just a map of a particular territory. As we have seen, learning to construct and use memory maps gives the subjective animal a general conception of space, by which they can understand any relations in space by imagining the kinds of motion that would be involved in traversing or changing them. Similarly, the manipulative animal acquires the concept of geometrical structure.

The subjective animal’s general understanding comes from the structure of the memory system on which imagination is based, because the same kinds of behavior generated in similar situations have the same kinds of effects. That is what the spatial structure of the world contributes, and thus, as behavioral schemata evolve by reinforcement selection, the connections in the memory system internalize those general relations. Their internalization is the subjective animal’s conception of space.

The memory system in manipulative animals internalizes a further spatial aspect of the world in the same way. The same kinds of manipulation have the same kinds of effect on objects with the same kinds of geometrical structures. Rotating them in any of the three independent planes possible leads to similar sequences of telesensory images, for example, and likewise for bringing the object closer or moving it to the side. The appearance of hollow objects from the outside can be used to infer how they would appear from the inside. Similar shapes also cause similar tactile images when the fingers move relative to the object in certain ways.

Thus, by recording objects with similar geometrical structures together as the same generalized object images, there would be a “map” of the consequences of manipulation that would work for all objects of that kind involving that kind of manipulation. And the different sequences of images involved in manipulating them in different ways could be interconnected like the sequences of local images representing different directions of locomotion from the same scene, because changing the direction of rotation would have effects that parallel changing direction at some point in the territorial map.

The contained form of reproductive causation in which behavioral schemata evolve by reinforcement selection, which has been described in subjective animals, would enable manipulative animals to acquire the ability to manipulate objects in all ways that are physically possible for the kinds of hands they have, as long as they enabled the animal to control some relevant condition and were reinforced by the memory circuit (in alliance with the goal selection system). Thus, they would internalize structural global regularities about change in the world as part of the structure of their structural imagination. And manipulative schemata would tend to evolve in the direction of more abstract representations of the geometrical structures of objects, though there may be a limit to how useful such abstract understanding is in ecological niches where they do not help satisfy desires.

Structural imagination would also enable manipulative animals to learn complicated tasks involving hand-eye coordination, if that were useful in satisfying desires. The motor output is sent to the hands from an image of the hands that is part of the body image, and by sending separate motor commands from different parts of those images of the hands to different parts of the hands, it is possible for the behavior generator to generate very complex bodily movements in relation to objects in the object image. A set of motor commands is sent each moment and it can generate long sequences of such sets of such motor commands.

To be sure, the behavior generator for the hands needs a “schema” for each kind of behavior, but such manipulative schemata can also be learned from experience with the world, that is, by operant conditioning and the evolution of behavior schemata in the behavior generator, just as subjective animals learn complex routes through their territories.

Manipulative animals may even learn a behavioral schemata that enables them to recognize how other manipulative animals are manipulating objects. That is, when they learn to manipulate objects in certain ways, they also learn to recognize when other manipulative animals are manipulating objects in the same way. Manipulative animals with that skill could not only recognize kinds of manipulation in other animals, but could also understand the manipulation in the sense of knowing how to act the same way. Since manipulation can be generated covertly, manipulative animals would be able to call up telesensory images from memory of another body behaving in a certain way, so that the behavior it is rehearsing could be seen from the outside, where it may be easier to imagine how it would fit into the current scene.

However, far from being a mere recording devise for learning complex manipulative tasks or for viewing aspects of objects in imagination, the most general new power is the capacity to think about objects as having geometrical structures. With abstract concepts of geometrical structure, particular objects can be represented in structural imagination by adding whatever details about the particular object may be relevant to a general concept. Cups hold water in the same way, and that general conception of cups becomes a formula for memories of particular cups. And their intuitive understanding of geometrical structure would enable manipulative animals to think about objects in terms of how they would interact with other objects in the local scene because of their geometrical structures, that is, as an understanding of structural causation. Thus, an ape can see branches from trees as something to be assembled as a bed to sleep comfortably, or, as in the case of Kohler’s ape, see how a box and a stick would enable it to knock down a banana which was otherwise out of reach. It is, in other words, the capacity to see objects as tools or machines. That is the sense which objects in space are seen as having geometrical structures.

The goal selection system serves the function in the manipulative animal behavior guidance system as the subjective. It attaches desires to objects. Such desires are actually dispositions to use certain behavioral schemata in relation to the object identified, and thus, not only can manipulative animals have new or refined kinds of desires to attach to objects, but new kinds of problems can be solved in satisfying them. Though it may not be possible to remove an obstacle that is frustrating the satisfaction of a desire by locomotion, it may be possible by manipulation. For example, primates can figure out how to unlatch gates, though dogs cannot.

The possibility of the manipulative level of neurological organization. The functional description of the manipulative animal system of representation shows how a higher level of neurological organization would make animals more powerful in a basic way, by giving them the use of structural causation. Since the manipulative level is functional in a profound way, all that is required to infer its inevitability is sufficient reason to believe that such a neurological structure can be tried out as a random variation on the brains of subjective animals.

The possibility of the higher level of part-whole complexity is not very problematic in this case. Since subjective animals already have the kind of memory that can record and recall images in sequence according to the kind of behavior that causes them, it requires only two kinds of changes, one each in the behavioral output and sensory input systems. One change is the addition of four new subjective level behavioral output systems, one for each hand, installed as parts of the behavior generator for the body as a whole. The other change is some way of handling as many as four object images within the local image of the sensory input system.

These changes are less radical than what was needed to cause earlier stages of chordate evolution, because they do not involve a further centralization of the whole nervous system.

In order to use telesensory input to guide locomotion, the functions of all the local reflexes of the somatosensory chordate's nervous system had to be centralized in the non-mammalian vertebrate brain where the interaction between sensory input and behavioral output could be separated from the goal selection system.

And in the evolution of subjective animals, the three systems of the animal behavior guidance system (behavioral output, sensory input, and goal selection), which were located in the hindbrain, midbrain and forebrain in non-mammals, had to be centralized in the mammalian forebrain, where the behavioral output and sensory input systems could each be composed of several telesensory level brain mechanisms and interconnected so that behavior could be generated both covertly and overtly.

Centralization is not, however, the only way a higher level of part-whole complexity can be introduced in neurological mechanisms. Instead of housing multiple lower-level systems alongside one another as part a whole new structure, it is possible to introduce a higher level of part-whole complexity by multiplying parts within the main systems of an existing animal system of representation. Though this is a less radical way of organizing nervous mechanism on a higher level of part-whole complexity, it is just as much the cause of a new stage in animal evolution, because it is the fountain of a whole new range of powers that can evolve gradually over a long period of time.

Since a relatively minor change of this kind is surely within the range of random variations that can be tried out by the biological behavior guidance system, we could take the possibility of mammals with structural imagination for granted and conclude that manipulative animals are inevitable. But there is further confirmation, because the kind of manipulative mammal we are looking for does exist on earth, and its brain does have just the kinds of structures we expect.

The mammals that most obviously have structural imagination are primates. But they may not be the only manipulative animals. It is possible that elephants also have a kind of structural imagination for guiding the behavior of their trunks.

In the primate brain, at least, the is good evidence of both kinds of changes in the mammalian brain.

In the behavioral output system of primates, there is clear evidence of multiple behavioral output systems within the behavior generator for the body as a whole.

And there are just the kinds of changes in the sensory input system we should expect for accommodating object images within the frame of the local image.

Behavioral output system. Since the evolution of hands for manipulating objects is the clearest evidence of a higher level of neurological organization, let us begin with the behavioral output system.

The body image for issuing overt motor commands to all parts of the body includes the primary and supplementary motor cortex as well as the somatosensory cortex, and as we might expect, the areas devoted to the hands in the primate brain are much larger than in non-primates. They are the hand images for overt behavior in the functional diagram.

There are presumably also larger areas for the hands in the covert body image (that is, in the premotor neocortex and in the anterior geniculate neocortex) for generating covert manipulation in parts of the body as a whole.

The new hand images of the behavioral output system are connected to the behavior generator in the same way as the rest of the body, for the hand images are just part of the body image. That is, manipulation in each hand is generated as a separate part of the circuit from the anterior neocortex through the corpus striatum, the ventral lateral and ventral anterior nuclei of the thalamus, back to the anterior neocortex. Yet these hand behavior generators are just part of the body behavior generator. That is how we expect the higher level of neurological organization to be accomplished from the functional diagram.

In mammals, behavioral schemata are contained in the frontal neocortex, and in primates, there is such a great overall increase in the size of the frontal neocortex that primates are often said to have a new "prefrontal" lobe. (The prefrontal neocortex is just anterior to the frontal eye field, including areas 9 and 10 as well as 45 and 46, and all these areas granular, having all six layers of cortex.) These new areas of neocortex, like the frontal neocortex of non-primates, are available to the behavior generator, because they are parts of its circuit for generating behavior.

They all project to the putamen of the corpus striatum, and because the corpus striatum projects to the ventral anterior nucleus of the thalamus, the circuit is completed by the projection from the ventral anterior nucleus back to the frontal neocortex. This circuit lines up 2-D arrays of neurons in each structure it passes through, and thus, as one cycle of interactions through the circuit follows another, the spatial complexity of the behavioral schema in the frontal neocortex can be translated into a temporal sequence of motor commands. But since the projections to the putamen tend to consolidate different areas of the neocortex that are involved in generating each part of the body, there are distinct circuits within the circuit for the body as a whole for generating the behavior of each hand separately.

The corpus striatum is the central organ of the behavior generator, and there are indications of special provisions for generating manipulative behavior. The corpus striatum, as we have seen, uses the active behavioral schema to combine the local image containing (as we shall see) the object image with a similar projection from the hand images and body image to issue precise motor commands to relevant parts of the body.

Since the object images are contained in the local image as their frame, they are supplied to the corpus striatum via their projection to the caudate nucleus, that is, as what the manipulative animal perceives.

However, in order to issue motor commands to the hands that coordinate their movements with visual input from objects in the scene, the behavior generator must be able to identify the parts of the visual input that are coming from the hands so that it can guide the hands in relation to the objects.

No such identification of telesensory input is required for locomotion, since the animal does not need to be able to see its body to move around in space relative to there objects.

But manipulation generally involves hand-eye coordination, and thus, in order to facilitate it, we should expect that the projection from the local image to the behavior generator circuit (via the caudate nucleus) would enable the animal to identify which part of the local image is coming from the hands.

This would account for the primate's new and highly unusual projection from area 9 of the prefrontal cortex, just anterior to the frontal eye fields, to the caudate nucleus. This is the only projection from the frontal neocortex to the caudate nucleus (where the corpus striatum receives the representation of the object).^xxxiii It could provide markers in the local image indicating where the hands should be located. (There is, of course, no comparable problem using tactile sensations to control manipulation, because they have a fixed location relative to the hand and body images.)

Structural imagination requires the capacity to generate manipulation both overtly and covertly, and their effects on the brain must be parallel (despite being so different in their effects on the body), because in order for memory groups to have labels by which covert manipulation can recall them, those memories must have been recorded according to the overt manipulation that was causing them when they were received. That is how spatial imagination works, and now we are assuming that the same brain structure can also be used for as the memory system for structural imagination, that is, with manipulation and not just locomotion.

The crucial brain structure for imagination is the cingulate gyrus, which is part of the memory circuit (starting from the anterior temporal neocortex, proceeding though the hippocampus, fornix, and anterior nucleus, and then back to the cingulate gyrus, which has rich interconnections with adjacent areas of neocortex). Since the behavioral output system contains four hand images within its body image, the hand images have the same connections to the cingulate gyrus as the body image used in spatial imagination, and they have similar effects.

Both hand and body images for overt behavior project from the frontal neocortex to the anterior cingulate gyrus (by way of association fibers from the motor and supplementary areas), and both the hand and body images for covert behavior also project from frontal neocortex to the anterior cingulate gyrus (by way of the association fibers from the premotor neocortex and frontal neocortex where behavioral schemata are stored and activated).

The anterior cingulate gyrus is (agranular) motor-type neocortex, like the rest of the anterior neocortex, and it projects to the posterior cingulate gyrus, which has rich interconnections with the sensory and parietal areas of neocortex in the posterior cerebrum. Since both anterior and posterior regions of the cingulate gyrus are part of the memory circuit, it is likely that the cingulate is where images are recorded in sequences with behavioral labels for both spatio-temporal and structural imagination.

In the case of structural imagination, the only difference (apart from effects on images in the sensory input system) is that the behavior is manipulative, rather than locomotor. That is, when object images are recorded in memory, behavior is overt and object images are recorded with labels indicating the kind of manipulative behavior, and then, when behavior is covert (and the projection to the anterior cingulate gyrus from the hand and body images for overt behavior is not active), there is still input to the anterior cingulate indicating the kind of behavior (via the projection from the premotor and frontal neocortex). Thus, covert behavior gives the anterior cingulate gyrus sufficient information of the right kind to call up memory groups by their behavioral labels.

It should be emphasized, again, that most of the detailed neural connections required for the memory labels can be acquired from experience with the world, since the late phase of neurological development, called “learning,” is a contained form of reproductive causation in which behavioral schemata evolve gradually in the direction of greater power to satisfy desires by a form of natural selection through reinforcement.

That is, when a behavioral schema is successful in generating behavior that satisfies some desire, the memory circuit (using criteria built into it with its close and ancient connections with the seat of desire) ties the active neurons in every area of the neocortex together in a memory group (by the growth of synapses among them), so that when some significant portion of them is activated again, the whole group of neurons tends to fire. This occurs not only in the anterior and posterior neocortex, but also in the cingulate area and its connections to them.

Thus, when behavioral schemata that are responsible for successful actions on objects are naturally selected, connections are established through the cingulate gyrus between the kinds of behavior involved and the images of the sensory input system that are involved so that those images are labeled by the relevant kind of behavior. The labels are simply part of the behavioral schema that is naturally selected by reinforcement.

Such labels can, as we have seen, become generalized as abstract, intuitive concepts about the structure of space and the geometrical structures of object in space whose meaning is spelled out by how sequences of images represent the effects of locomotion and manipulation.

What makes structural imagination different from spatial imagination is that, instead of covert locomotion and turning calling up local images in sequences to represent their effect, covert manipulation (such as rotating or bending the object) is calling up telesensory and tactile images of object in sequences to represent their effects. But that difference means that they must have different effects on images in the sensory input system, and thus, it remains only to see how the object image is installed.

The sensory input system. In the sensory input system, the higher level of neurological organization should show up as a new capacity for representing objects within the local image that keeps track of how the geometrical structure of each is affected by rotation, translation, and other forms of manipulation. There is evidence for such object images in the memory circuit, but in order to see what is different, let us begin by recalling how the local image is constructed in the subjective animal system of representation and consider what is added in the manipulative animal.

The telesensory images registered in the sensory neocortex (the striate neocortex for vision and the superior temporal neocortex for hearing) are assembled as parts of a local image, as we have seen, in the inferior parietal neocortex, using projections from the body image as input about the current bodily condition.

In primates, however, there is additional input about the current bodily condition, because the body image now contain four hand images, each with its own somatosensory input. This information is used in a new way to construct the local image, because it reveals the shapes (and certain other properties) of objects in the local scene as well as their precise locations. Touch is a new (extroceptive) sensory modality, along with the other modalities, and its tactile images must be assembled as part of the local image as well. Somatosensory input from the hands is transformed into tactile images in the superior parietal neocortex, posterior to the somatosensory neocortex, and its connections to the inferior parietal neocortex make it possible to include them as another part of the local image, along with visual and auditory images.

The inferior parietal area also receives information from the frontal eye fields about the direction of fixations of the eyes, so that visual images from the different fixations of the eyes can be assembled into a visual appearance of the whole scene. There is evidence from primates that fixations of the eyes mark targets for manipulation in the representation of the current scene before it is projected to the behavior generator (that is, to the corpus striatum by way of the caudate nucleus).^xxxiv

Furthermore, there is abundant evidence that local image is required in order to guide the behavior of the hands in relation to objects. The object image is contained by the local image, just as the object itself is located in the local scene, and the local image is assembled in the inferior parietal neocortex. Lesions in the inferior parietal lobe of one hemisphere may cause subjects to neglect entirely the limbs on the side of the body it controls. Even when the hands are not paralyzed by the lesion, patients may be unable to locate objects on that side of their bodies or to identify them by touch (or visually). Lesions may show up, however, only in the inability to put one dimensional units together as a two dimensional configuration, for example, when drawing.^xxxv

The local image is, however, just the frame for the object image. Structural imagination calls up sequences of telesensory and tactile images of objects within the local image according to the kind of covert manipulation. (Imagine turning a cup of water upside down.) Thus, the object images themselves must be handled in a different way from local images by the sensory input system. They must be contained in the local images like objects contained in the kind of space that mammals can understand. There are four pieces of evidence that the posterior cerebrum contains the new way of handling images that we expect.

(1) There are two changes within the memory circuit itself that suggests that images are being recorded as groups in a new way. The object image needs a new pathway, because its telesensory and tactile images must be recorded as groups separately from the local image if the later is to serve as its frame. The hippocampus, which is the staging area for forming neurons into memory groups, projects by way of the fornix to the anterior nucleus of the thalamus, which is basically a relay back to the cingulate neocortex. But this projection divides into two pathways, one that passes through the mammillary body and thence to the anterior nucleus, and the other that proceeds directly to the anterior nucleus. In primates, the later, direct pathway is relatively larger than in other mammals. The former, indirect pathway must be responsible for the local image, because the mammillary bodies are known to be essential to spatial orientation. If the images being processed through it were all oriented as part of the local image, then the images passing through the direct pathway could be processed independently of the local image, as if the local image were its frame.

(2) There is further evidence that the expanded, direct projection of the fornix to the thalamus is for processing the object image, because it sends fibers not only the anterior nucleus of the thalamus, but also to a new (or expanded) nucleus of the primate thalamus, the lateral dorsal nucleus. The lateral dorsal nucleus is only indistinctly separated from the anterior nucleus and appears to be a posterior extension of it. The lateral dorsal nucleus has two-way connections with the cingulate gyrus, parietal lobe and, perhaps, even the occipital cortex. Such direct connections with the parietal and occipital cortex are not found in other mammals, but they would make it possible to connect the separate object image to the local image as its frame. The result would be that the object represented by the object image would appear to be located somewhere in the local scene represented by the local image, that is, as located in the space of which subjective animals have a conception.

(3) Just posterior to the lateral dorsal nucleus of the thalamus is another thalamic nucleus newly prominent in primates, the lateral posterior nucleus. It projects to the superior parietal neocortex, where tactile images are analyzed, and that suggests that its function is to help integrate tactile images as parts of the object image, rather than the local image. The lateral posterior nucleus has connections within the thalamus to the pulvinar, which projects to the inferior parietal (and occipital) neocortex, on one side, and with the ventral posterior nucleus, where somatosensory input is relayed to the hand images, on the other side. Thus, its function seems to be connected with manipulation, just as the object image would require.

(4) Finally, there is a new, direct projection found in primates from the anterior temporal neocortex to the pulvinar.^xxxvi The anterior neocortex is the staging area for all input to the hippocampus and the only area of neocortex that does not receive a projection from the thalamus, and thus, it contains information about both the local image and the object image. The pulvinar, to which it projects, is the nucleus of the thalamus (just beneath the lateral dorsal nucleus) which projects to the parietal and occipital cortex, where the local image and the object image are processed. It is, therefore, a new circuit through the neocortex and thalamus (from the parietal/occipital neocortex to the anterior temporal neocortex to the pulvinar and back to the parietal/occipital area), and its function could well be to integrate the object image into the local image.

There are various ways in which these circuits might work in detail, but taken together, these four prominent changes in the posterior primate cerebrum are just what the sensory input system would need, if it were able to processes telesensory and tactile images as parts of an object image independently of the local image. They can be taken as evidence, therefore, of the new circuit between the object image and memory depicted as contained by the local image in the functional diagram of the manipulative animal behavior guidance system.

Nor is there any reason to doubt that the object image can handle as many objects as there are handles, which would put it on a higher level of neurological organization in the same way as the behavioral output system.

These differences between (higher) primate and non-primate brains suggest just the kind of higher level of part-whole complexity we would expect of animals with a structural imagination that have evolved from subjective animals. It seems that there are multiple channels through the behavioral output systems of the subjective animal system of representation which could be handling each of the hands separately as parts of the body as a whole. And there is a new way of representing the objects they manipulate as part of the local image. Thus, the cingulate neocortex has connections to both systems of just the right kinds needed to record and recall sequence of telesensory and tactile images as object images according to covert manipulation. Since this way for random variations to try out a higher level of neurological organization is not problematic, given that chordates sets up nervous system using 2-D arrays of neurons as units, we may take this as evidence that such a level of neurological organization is possible. Since it is possible, we infer that the evolution of animals like higher primates is inevitable.

The gradual evolution of primates. That primates are more powerful than other mammals in the way that is implied by having structural imagination is, perhaps, patent in the vast superiority of their hand-eye coordination, but there is not much data about their cognitive capacities.

The most famous evidence of structural imagination is Kohler's ape, which put one box on top of another in order to be able to use a stick to reach a banana. Moreover, when monkeys or apes are provided with paints and a canvas on which to paint, they enthusiastically construct geometrical structures of bright colors, whereas other mammals do not. It has been obvious for so long that they like to play with unchanging geometrical structures of matter that such behavior is often called "monkeying around" with them.

But more systematic evidence is conceivable. Primates should be able to count (or keep track of) more objects in the current scene than other mammals. And a properly trained primate should be able, for example, to tell how an object is oriented after a series of rotations. That is, if a primate were conditioned to pick out a distinctive face of a die and the die were rolled, then it should be able to learn to point to the side of die that the distinctive face is on, even when it cannot be seen. But other mammals should not be able to do so. Or primates should be able to pick out from a group of similar objects the one that is the folded up version of a pattern laid out flat, as in standard tests of spatial imagination, while other mammals cannot. Experiments like these would show that primates can make the inferences implied by the mechanism described in the last two chapters as structural imagination.

Evidence that primate evolution is due to the greater power afforded by structural imagination can also be found in the history of evolution, although it may not be obvious at first, because it seems possible to explain primates a mere adaptation to a special habitat. That is, it might be argued that the evolution of primates from mammals can be explained on the model of the evolution of amphibians from fish, of reptiles from amphibians, or of birds from early dinosaurs. In these cases, as we have seen, there is no change in the part-whole complexity of the nervous system, but merely an adaptation of the same kind of animal behavior guidance system to new habitats — to life on land and in the air. In other words, the significant changes occurred in the body, not the brain.

Living in trees is certainly a special habitat, and there is no doubt that primates have bodily characteristics that are well adapted to it. All primates have hands that are capable of grasping structures on trees. They all have acute binocular vision, with both large eyes directed forward. More generally, they are active and restless animals which react quickly to stimuli.

Living in trees is not, however, just a specialized environment. It is also a more demanding environment in which the power that comes from structural imagination would be richly rewarded. Arboreal life is surely possible without having a structural imagination. Indeed, the earliest ancestors of primates probably did not have structural imagination. They stem from which all the species of mammals radiated were insectivores, and primates are more closely related to those insectivores than any of the other classes of mammalian species (except possibly bats). The species from which primates are thought to have evolved has a living remnant, the small, primitive tree shrew (Tupia), and it is highly unlikely that tree shrews have a structural imagination. But given the demands of their arboreal habitat, this lineage of mammals must have had a "need" for structural imagination, if the required random variation was within the range of those being tried out, for it would have made them more powerful animals. And the need would account for the evolution of structural imagination, given that evolutionary change is how reproductive cycles add up in space over time. That means, however, that there must be some juncture in the evolution of primates at which it was added.

There is, indeed, fossil evidence of such a development, for there have been two radiations of primates in forests. The first radiation was that of the prosimians, represented by lemurs and tarsiers, about 65 million years ago during the radiation of mammals. Then there was a second radiation, the anthropoids — represented by the New World monkeys, the Old World monkeys, the great apes and humans — roughly 40 million years ago. As a result of the first great primate radiation, there were lemurs as large as chimpanzees, and anthropoids are thought to have evolved from lemurs of some kind.

Although prosimians typically have elongated flexible limbs with grasping hands and adhesive pads for grasping branches firmly as well as binocular vision, there are marked changes in anthropoid primates. Anthropoid eyes are directed forward more completely. Most anthropoids are able to sit in an upright position, which frees their hands for manipulating objects. The thumb is set apart from the other digits more extremely. Arm joint, elbow and wrist are capable of more rotation, so that the hand can be rotated in all directions possible in space. These are indications of a new capacity for manipulation, beyond a mere grasping reflex, which is probably all that prosimians have.

Moreover, only a general increase in power can explain why the radiation of anthropoid primates replaced prosimians in all but the lowest-energy ecological niches. It cannot have been tapping a new source of energy, because primates of all kinds eat almost anything edible in their habitat.

The actual history of the evolution of higher primates confirms, therefore, that they are a later stage in the evolution of multicellular animals, with a higher level of neurological organization. They are not merely better adapted to their environment, but inherently more powerful as animals. Thus, we would expect a primate radiation out of the forest. Much as mammals took over the high-energy ecological niches once occupied by dinosaurs, anthropoid primates should invade ecological niches outside the forest, displacing less powerful animals from those sources of free energy.

The almost complete absence of anthropoid apes from ecologies other than dense rain forests does not show, however, that there has not been a radiation of primates. Human beings are a kind of anthropoid primate that are adapted to tapping energy in this new environment. Although they have occupied all the other ecologies on the planet, they are not a mere radiation of primates, because they are so powerful that their radiation is now even displacing the great apes from their original environment. The primate radiation into the grasslands occurred long ago and has already led to another stage of evolution, which has already displaced anthropoid apes from this new environment. Indeed, as we shall see, the evolution of human beings involves such a revolutionary change that it starts yet another ladder of evolutionary stages in a different direction — as different from the stages of neurological evolution as those stages are from the stages of biological evolution.

8 Linguistic stage (primitive spiritual animals). We have followed the series of levels of neurological organization, tracing how multicellular animals evolve, stage by stage, from somatosensory animals, through telesensory and subjective animals, to manipulative animals. In each case, the increase in animal power came from increases in the capacity of the animal system of representation to internalize spatial aspects of the world. We now take up the final three stages of evolution leading up to beings like us. Though they continue the series of stages caused by levels of neurological organization, they also involve something quite novel. Each of these last three stages is also caused by a higher level of neurological organization, but they are levels of organization in a linguistic system of representation, and the function of language is not just how it increases the power of individual animals, but also how it increases the power of groups of individuals. What is novel about these stages is that they are also the evolution of spiritual animals.

The linguistic system of representation is built on the animal system of representation, but it does not increase the power of individual animals, at least, not originally. Just as higher levels of neurological organization introduced, first, spatial imagination and, then, structural imagination, to the animal system of representation, so each of these three yet higher levels of neurological organization introduces new forms of imagination in the linguistic system of representation (naturalistic, rational and philosophical imagination, as we shall see). And just as the new forms of imagination in the animal system of representation made individual animals more powerful by enabling them to adapt their behavior to spatial aspects of the world, so these new forms of imagination in the linguistic system of representation do eventually make individual animals more powerful by enabling them to adapt their behavior to further aspects of the world. However, such contributions to the power of individual animals are, at most, only half of the story. (The new forms of imagination in the linguistic system of representation are the blue panels in the accompanying diagram.)

The linguistic system of representation is not just a new kind of imagination in the individual, but also a new form of interaction among individuals. Linguistic interactions among individuals make groups of animals more powerful as a whole, and that is the original function of language, from which the increase in individual power derives. Indeed, it is a source such great power that groups of language using animals constitute animals on the social level of biological organization. It is, as we shall see, a new form of life, and such groups will be called “spiritual animals.”

What makes these final three stages different from all earlier stages is that organisms are evolving on two levels of biological organization at once. Not only do individual members, by their reproduction, impose natural selection on themselves at the individual level, but the social level animals they constitute impose natural selection on themselves at the social level by their reproduction at the social level. Thus, gradual evolution during these final three stages is change in the direction of the natural perfection of organisms at both levels of biological organization at once. And since they evolve together, there is also a natural perfection about their combination.

To mark this difference, these final three stages will be called “spiritual stages of evolution,” distinguishing them from the multicellular animal stages of evolution just discussed, and the animals evolving on the social level will be called “spiritual animals.” The appropriateness of calling the “spiritual” will be explained after we explain the function of language.

Since these final three levels of neurological organization are also stages in the evolution of a new kind of organism on the social level, the first stage has two ontological causes at once, according to this ontological explanation of evolutionary stages as a revolutionary global regularity, both a higher level of neurological organization and a higher level of biological organization. Once spiritual animals have evolved, subsequent evolutionary stages are caused ontologically by higher levels of neurological evolution in the individual multicellular animals, though their higher levels of organization are also evident in the linguistic representation they exchange.

Primitive spiritual animals. Primitive spiritual animals are groups of primates with the capacity to use a language of natural sentences (that is, sentences with a simple subject-predicate grammar). The use of language is functional, as we shall see, because it enables their behavior to be coordinated so that they can act as a whole. It is a new animal behavior guidance system that is possible only at the social level of biological organization. But language requires a higher level of part-whole complexity, the linguistic level of neurological organization, and such a higher level is possible, as we shall see, because it evolves within the faculty of imagination. The new form of imagination, called “naturalistic imagination,” gives subjective animals the conception of a state of affairs in the natural world, and that enables them to understand efficient causation.

Rational spiritual animals. Rational spiritual animals are also animals at the social level of biological organization, but they have the capacity to use psychological sentences (that is, sentences with predicates formed of verbs of propositional attitude, such as “believes” and “desires,” together with complete sentences). We shall see what its original function was, and how it too was possible because of a higher level of neurological organization in the faculty of imagination. It is aptly called the reflective level of neurological organization, because this higher level brain gives subjective animals the conception of a psychological state and enables them to think about such states as causes of behavior (and belief). The new form of imagination it gives them will be called “rational imagination,” because as they use psychological sentences to think about the causes of their own behavior, the causes of their behavior become reasons. (Reasons are causes of behavior that are represented as causing behavior as part of the very process of causing behavior.) Rational imagination gives them an understanding of rational causation, but since that enables them to understand arguments, it is also the foundation for a new form of evolution by reproductive causation, namely, cultural evolution, which is contained within spiritual animals. Thus, reason makes language a very powerful animal behavior guidance system, which takes over responsibility for behavior at both the individual and social level.

Philosophical spiritual animals. Philosophical spiritual animals are social level animals in which the arguments accumulated as culture have evolved a higher level of organization. That is, in philosophical arguments, all the arguments of the rational spiritual level are organized as parts of a single argument. That promises a new way of proving that propositions are true, and thus, it is a new way of discovering the true and the good, one that yields necessarily truths in one way or another. Though this is a stage of cultural evolution, it gives the members of the spiritual animals in which it exists a higher level of rational imagination, and thus, it is also the philosophical level of neurological organization. But there are, as we have seen, two ways of constructing such philosophical arguments, epistemological and ontological, and only one of them is able to succeed in the end.

Primitive spiritual animals evolve at the first spiritual stage of evolution. In order to show that a stage of evolution is inevitable, according to reproductive causation, it is necessary to show that the higher level of part-whole complexity in the structure of evolving organisms is both functional and possible.

The higher level must be functional in the sense of opening up an entire new range of powers for controlling relevant conditions, which can evolve gradually over the stage, and it must be possible in the sense that the higher level of organization can be tried out as a random variation in the evolving organisms.

In the case of primitive spiritual animals, however, there are two kinds of higher levels of part-whole complexity, a higher neurological level and a higher biological level, and the simplest way to explain their function is to assume, for now, that the linguistic level of neurological organization is possible, and to explain its origin by its functions, that is, by how it was naturally selected.

That will put us in a position to consider the nature of spiritual animals in the second section.

Only in the third section will I take up the issue about the possibility of the linguistic level of neurological organization, and that will include an explanation of the structure of the linguistic brain and how naturalistic imagination affords an understanding of efficient causation.

Finally, in the fourth section, I will consider the empirical evidence about the gradual evolution of primitive spiritual animals on earth.

Function of the linguistic level of neurological organization. The original function of a level of neurological organization higher than manipulative animals is a power it gave to entire groups of such animals, and thus, the easiest way to explain its function is to consider how spiritual animals evolved from animal societies. Thus, we begin with the radiation of primates. Such a radiation was inevitable, once higher primates had evolved, and it would lead some higher primates out of the forest, if it was possible, because that would open up new sources of free energy.

With the addition of structural imagination, higher primates were more powerful than other mammals, and though they started off simple, uniform and weak, manipulative animals gradually became more complex, diverse, and powerful. Such gradual evolution is change in the direction of maximum holistic power at both the level of the organisms and the ecology, which is natural perfection for organisms of their kind. Thus, as each primate species became as powerful as possible at controlling relevant conditions in its ecological niche, new primate species were added, dividing up the sources of usable energy and invading new habitats, and species generally adapted to one another, maximizing the use of the available free energy to fuel reproductive cycles generally. It was inevitable, because, as we have seen, reproductive causation always makes every possible increase in power actual.

Hominids. The radiation of primates beyond their original arboreal habitat was just a special case of species tapping new sources of free energy. As primates diversified to fill all possible ecological niches, some invaded the grasslands beyond the forest to tap the energy available there (such as grass seeds, berries and small animals). These primates evolved into hominids as their bodies and behavior became as powerful as possible in controlling the conditions that affected their reproduction in this new ecological niche. The traits that primates would evolve, once they invaded the grasslands, are predicable, in principle, because only a certain range of random variations can be tried out by their biological behavior guidance system and the conditions affecting their reproduction were fixed by their new ecological niche.

Carrying clubs. The main obstacle to occupying the grasslands were carnivores, such as lions and packs of wolves. The ungulates already inhabiting the grasslands protected themselves by traveling in herds and running away from these predators. But primates are relatively slow-moving, which made them easy prey. However, grasslands were not closed to them, because, as manipulative animals, they had another means of protection, not available to other mammals. They could carry clubs into the grassland with them and beat off carnivores that tried to prey on them.

Social life. This means of protection would be effective, however, only if several adults traveled together carrying clubs. Predators might still overcome one or two primates with clubs, especially if they were parents with children to protect. However, several adult primates carrying clubs could attack simultaneously from different directions, and that would thwart carnivores that were adapted to preying on ungulates, including not only the most ferocious, but also packs of smaller predators.

The need to stay together in a group would not be a great obstacle to their evolution, because group life in the forest had already given higher primates desires that enabled multiple families to live together in groups. They had instinctive desires that would establish a dominance hierarchy among them, and conflicts would be resolved by some members having power over others. Thus, grassland energy sources were open to any small group of primates that carried clubs and had learned how to wield them. This variation was well within the range of those being tried out randomly by existing primates, especially considering that, at first, nomadic primates could return to the forest at night for protection.

Since neither club-carrying nor social life was optional for nomadic primates, the evolution of two kinds of traits were inevitable, one a change in the biological behavior guidance system and the other a change mainly in the animal behavior guidance system set up by it.

Bipedal stance. The need to carry clubs entails the evolution of a bipedal stance in the primates that invaded the grassland. On the ground, primates were naturally disposed, like most mammals, to travel on all fours. And the further they could travel in gathering food, the wider the range of grasslands that they could invade. But nomadic primates could not travel on all fours, if they had to carry clubs along with them. As manipulative animals, however, they had another alternative. The precise control of muscles in their hands enabled primates to balance their bodies on two of their hands, leaving the other two hands free to carry clubs. Thus, the primates that invaded the grasslands would eventually acquire bodies suited to bipedal locomotion: random variations in embryological development that made them better able to balance their bodies on two legs controlled a condition that affected their reproduction and, thus, was selected as part of their biological behavior guidance systems. The primate predecessors of humans who walked upright, on two feet, are now generally known as “hominids”.

Although the traditional evolutionary explanation of bipedalism is also that it evolved for carrying things, this explanation is different. A century ago, Darwinians explained bipedalism by the need to carry tools. But that did not really explain bipedalism, because they attributed tool use to an increase in brain size or intelligence without being able to explain why an increase in brain size was necessary.

Sociobiologists have now dropped the assumption that brain size naturally increases, but their explanation does not make increasing brain size any more necessary. They claim that bipedalism evolved in order to carry the food required for the practice of food sharing. But that is no explanation, for they do not explain why hominids must share food. Apparently, increasing sociality has replaced increasing intelligence as the motor behind hominid evolution. (See, for example, Wilson and Lumsden 1983, pp. 10-12.)

To insist that the cause of bipedalism was the need to carry clubs for protection is not to deny that hominids also carried other tools. Nor to deny that they shared food. It is only to insist that bipedalism be explained by the function that made the trait inevitable, that is, by the one that predicts its evolution, rather than other functions which were made possible by its evolution. There is no reason to believe that bipedalism would have evolved to carry other tools or to share food, if nomadic primates did not have to carry clubs. And it would have evolved to carry clubs, even if it did not have those other functions.

Altruism. Another set of traits can be predicted by another function that needed to be served in their ecological niche. Protection from predators required not only traveling in groups, but also a disposition to use their clubs to assist other members of the group when they were endangered. Since this exposes the protectors to greater danger than sitting out the attack or running away, at least, in the short run, it is an example of altruism.

Altruism poses a challenge to explaining the evolution of nomadic bands of primates, therefore, because it seems that altruism cannot evolve by the natural selection of reproducing organisms. If individual animals are naturally selected by their success in reproducing, traits that benefit others at the expense of the animals conferring the benefits, then natural selection will eliminate individuals with those traits in favor of those who receive the benefits.

The altruism required of nomadic hominids resembles the bees’ use of stingers to protect the hive, but bees cannot be the model for explaining primate altruism. Defender bees die as they use their stingers to protect the hive, and that can be explained in social insects, because individual bees are parts of a multisomatic organism set up by way of a single fertilized egg cell. By including some members with stingers, the insect colony is able to do the non-reproductive work of protecting the hive as a whole. But hominid groups are not multisomatic organisms, because their member continue to reproduce sexually as individuals. Thus, another explanation is needed for the trait of protecting other members of their nomadic group.

The received solution to this puzzle about altruism is called “kin selection,” but it depends on a theory of evolution, called the “selfish gene,” which is incompatible with reproductive causation. The received view is, however, pointing to a relevant cause, which is explained in another way by reproductive causation. Though it does not quite explain the phenomenon of altruism in hominids, it will serve to introduce a cause that does make altruism inevitable.

What makes it appear that the gene is the unit of selection is, as we have seen, the sexual mixing of lower level structural causes in the process of reproduction, for it means that as organisms are evolving greater power, natural selection is focused on only certain of their genes (or chromosomes), which distinguish individuals from one another. Sexual reproduction is a way of internalizing reproductive causation so that lower level structural causes within the organism continue to evolve as the organism goes through reproductive cycles. And thus gradual evolution can be seen as genes competing with one another to appear in the next generation by the traits that are their non-reproductive structural effects, that is, as “selfish genes.”

The selfish gene theory explains altruistic behavior by the fact that siblings are likely to share the same genes. Thus, if altruistic behavior increases the likelihood of their siblings succeeding in reproducing more than it costs in terms of the animals own likelihood of reproducing, then the gene will be selected to appear in the next generation.

What the theory of kin selection of selfish genes is pointing to is another aspect of the evolution of the sexual mixing of genetic structures in reproduction. The obstacle to explaining the evolution of altruism is only an appearance that comes from failing to recognize that what is actually going through reproductive cycles, the primary structure, is not the individual multicellular animal, but the mating pair — or even the whole family.

The basic ontological cause of gradual evolution is, as we have seen, the reproductive cycle, because reproduction is what combines with space to make free energy scarce and that is how material structures that generate the whole cycles, including both reproductive and non-reproductive work, impose natural selection on themselves. But in the case of sexually reproducing animals, as we saw when the origin of sex was explained in eukaryotes (Stage 3), the individual animal is not that whole primary structure, because it cannot reproduce by itself. The individual organism must mate in order to reproduce, and that means, in effect, finding its other half. The mating pair is, therefore, the primary structure which is shaped by reproductive causation.

The primary structure is the “unit of selection,” and so the unit of selection is larger than the individual (rather than smaller, as the selfish gene hypothesis would have it), for it includes both members of the mating pair (though the pair that makes up a particular reproducing organism is not determined until they mate). Traits evolve in individual animals, because they help control conditions that affect the reproduction of the mating pair. Mating itself is the most obvious example of behavior that serves this function, but it includes, indirectly, at least, all the “sexually selected” traits required to mate, from suitable organs for the mating process to brilliant plumage in some male birds and fights over mates among male herd animals. Such genes can evolve, like any gene, because of their contribution to the maximum holistic power of the reproducing organisms of which they are part. It is just that the reproducing organisms of which they are part are the peculiar, disjointed primary structures of the kind entailed by sexual reproduction.

After the evolution of sex, therefore, what is evolving might be called a “composite organism,” or "composite primary structure," for the unit of selection is composed of more than one individual organism. And after the evolution of multicellular animals, the individual organisms may be in different generations. Reproduction is carried out by specialized cells, and thus, the mating pair does not necessarily die in reproducing sexually. Multicellular animals may, therefore, live side by side with their offspring, and when reproduction comes to depend on offspring being nurtured and protected by parents, the composite reproducing organism includes the whole family. The family is the primary structure that goes through the reproductive cycle (which is the ontological cause of gradual evolution), and traits evolve in its members because they control conditions that affect the reproduction of the primary structure as a whole.

Altruistic genes can evolve, like other genes, because they are structural causes of behavior in one, disjointed part of the primary structure, and they control a condition that affects the reproduction of the whole primary structure by promoting the reproduction of another individual organism of which the whole is composed. The disposition of children (and even grandchildren) to sacrifice for one another is just another way, along with caring for offspring, in which the same disjoint primary structure does the non-reproductive work that controls all the conditions affecting its reproduction as a whole. Like any gene, altruistic genes are working together with all the other genes of an organism to control all the conditions that affect its own reproduction as a whole. It is just that the primary structure, or reproducing organism in this case, is a collection of distinct multicellular animals.

Reproductive causation offers, therefore a ready explanation of altruism in the family (as an ontological explanation, if you will, of so-called “kin selection” on the “selfish gene” theory). But that is not quite an adequate explanation of the kind of altruism required for the existence of nomadic bands of hominids, because their protective altruism must extend beyond members of the family to primates that are not kin. Several families must band together in order to have enough adults for the protection of everyone, and in the long run, inbreeding among them is ruled out by its deleterious effects. As sociobiologists have noted, primates had already evolved mechanisms to prevent inbreeding, such as the disposition of young males to leave their home group at sexual maturity and seek mates in other groups, and hominids without some mechanism for spreading their genes beyond the nomadic band would not have been successful for long.

If strangers, rather than kin, are benefited by animals who sacrifice themselves altruistically, altruistic genes will make strangers who lack the altruistic gene more likely to reproduce, and that will make the primary structure (or “reproducing organism”) of which the altruistic individuals are part less likely to reproduce, given the scarcity of resources caused by population growth. A family of altruistic animals is likely to be invaded by “free riders,” who benefit from altruism without reciprocating, and altruism will be extinguished.

It is possible, of course, to conceive of mechanisms that would extend altruism beyond the family. For example, if altruism happened to be accompanied by a “tit-for-tat” policy of aiding only others who reciprocate, but not aiding those who do not, a group of altruistic animals would be able to resist invasion by “free riders.” Computer simulations suggest that such conditional altruistic behavior would enable altruism to evolve beyond the family. But to explain the evolution of an altruistic trait in a whole species in this way would require a series of different selection pressures whose origins remain unexplained. The altruistic gene must first evolve by kin selection in groups made up only of family members so that the “tit-for-tat” condition can be added later when for some reason family groups are joined by strangers. This is just the sketch of a possible explanation which depends on unexplained changes in the environment. In order to explain altruism among hominids, it would be necessary to fill in the concrete details of human evolution. And in the end, it would be merely a “just-so” story, which makes the evolution of hominids an accident.

There is, however, another explanation, which entails that the evolution of hominid altruism is inevitable. It is not an accident that the radiation of manipulative animals includes some that invade the grassland, because manipulation is only likely to evolve in animals living in trees. And their new ecological niche imposes a form of group selection on the nomadic primates. In other words, there is a primary structure, or "composite organism," that is even more inclusive than the family and is evolving by reproductive causation (though in this case, there are actually two units of selection (or primary structures), because the individuals or families continue to evolve by reproductive causation within them).

Under the conditions in which nomadic primates found themselves, there would be at least a weak form of group selection, and it would inevitably become stronger. What is needed is a disposition to protect other members of one’s nomadic band from predators even when the others are not members of one’s own family. Groups having some members who happened to be disposed to fight off predators, regardless who in the group was attacked, would be the groups that were most likely to succeed in acquiring energy-rich objects from the grasslands. Thus, altruistic protection of others from predators would evolve in individual primates.

The selection pressure at the group level was probably not very strong at first, because nomadic groups would tend to disband and regroup rather fluidly when they met or returned to forested regions where they were safe from predators. Groups that happened to have families with courageous altruists would be more likely to return whole, and that would tend to favor the altruists. The desire to carry clubs and protect others in one’s group would tend to evolve.

Group level natural selection would, however, become more powerful, because they would be less likely to disband. Groups with altruistic protectors would be more powerful in controlling relevant conditions as they formed bonds that made them stay together, because they would have established habits and routines that worked together more effectively in protecting against predators and controlling other conditions. And as groups became more powerful and more permanent, group level selection would become stronger, for they would eventually impose natural selection on themselves at the group level. Not only would the populations of those bands increase faster than those of other primates venturing into the grasslands, but the groups themselves would reproduce. Groups must divide up as their populations grow, because there is a limit to how many members can be sustained by the energy acquired from the amount of land that can be covered by wandering around. Hence, there would be organisms (or primary structures) going through reproductive cycles at two levels of organization at once: at the individual (or family) level and at the level of nomadic bands. And the reproducing organisms (or primary structures) on both levels would impose natural selection on themselves by their population growth and the scarcity it causes. Thus, while individuals continued to evolve functional traits that made them increasingly powerful as members of such groups, the groups themselves would evolve traits that made them increasingly powerful in controlling conditions which affect the reproduction of the group as a whole. That would include many traits in addition to the desire to protect other members of one’s group.

Limits of Social Coordination. Although motivating social, or even altruistic, behavior is not, therefore, an obstacle to the evolution of nomadic bands of hominids, there is nevertheless a severe limit on their power, because they are still just animal societies. This can be seen by analogy to multicellular animals.

On the individual level, animal power comes from two sources. One source is the size, shape, and strength of the body, and the other is the structure of its animal behavior guidance system. Both depend on its biological behavior guidance system, although the power of animal behavior comes from the geometrical structure it imposes on the motion and interaction of material objects in the region. We have seen how the animal behavior guidance system enables the animal to act on objects in space so that it structures the thermodynamic flow of matter from potential energy to evenly distributed heat.

On the social level, the power of a group has comparable sources. The size of its population corresponds to the strength of the body, and the mechanism for coordinating behavior corresponds to its behavior guidance system. Although in some ways, it is easy for the group to act as a whole on an object in space, say, by chasing it, there is a certain kind of structure that animal societies are not able to impose on the thermodynamic flow of free energy toward increasing entropy, even though it would make them more powerful. It is the coordination of members' behavior that would generate social level behavior like the behavior generated by manipulative animals. That is the function that explains the evolution of language.

What makes behavior animal behavior is that it acts on other objects in space, either to ingest energy rich object or for other purposes, and the function of the animal behavior guidance system is to adapt the spatial aspects of behavior to spatial aspects of the situation so that it controls the relevant conditions. Since the animal itself uses free energy to do work, the generation of bodily behavior is already one way of imposing a geometrical structure on the thermodynamic flow of matter in the region, and so when the body moves around in space and interacts with objects throughout the region, it imposes a further geometrical structure on the thermodynamic flow in the region. Manipulative animals are able to structure the thermodynamic flow even further by coordinating the behavior of its hands, and that points to the potential power of animal behavior at the social level: manipulative animal behavior is possible at the social level if the animal behavior of the members of the group can be coordinated.

Animal societies. By “animal societies,” I mean societies of animals, from schools of fish and flocks of birds to herds of ungulates and packs of wolves. Animal societies are so weak at the social level that they are not really animals at all. Groups of animals do have some power to control conditions in the world. It comes from the power of its members, and it can be increased up to a point by adding new members to the animal society. But animal power depends, because of the nature of animals, on adapting the spatial aspects of social level behavior to the spatial aspects of the situation, and that does not happen naturally in groups of animals. It requires a structural cause of some kind, that is, a social level animal behavior guidance system. Thus, the question is, Where is the material structure that would enable an animal society to behave like an animal on the social level? Or like a social-level manipulative animal.

The tendency toward randomness applies to animals like other objects that move and interact in the region. Solitary animals stay out of one another’s way, for the most part, and forage on their own, or, at most, in family units, so that the way their behavior adds up in space over time tends to even out their distribution in space.

To say that they are solitary is not to say that they are not social at all. Solitary animals often stake out territories from which to gather the energy they will need, and they defend it against conspecific intruders by a more or less ritualized fighting behavior.

Animal societies do exist, however, because some animals have instincts or desires that act like a force attracting animals of the same species to one another. Gregarious instincts are like gravitation, making the motion and interaction of such material objects adds up in space over time to the formation of social level objects in space.

But gregariousness results only in the minimal geometrical structure required to be a composite object in space, resembling gravitational objects, such as stars or drops of water, more than the kinds of material objects that can serve as structural causes. The disposition of fish to swim in schools and ungulates to run in herds are examples of such “gravitational” organizations at the social level. Though the members do not get very far apart, the spatial relations among the animals are continually changing at random.

In order to be a social level animal, the members of an animal society would have to act on objects at the social level like animals do at the multicellular level, and more power would come from acting like manipulative animals at the social level. Gregariousness itself is, perhaps, a way of acting as a whole. But its social level behavior is hardly up to the standard set by multicellular animals

In herd animals, the members’ desires to stay relatively close to one another includes the desire to start running when other members do. Thus, if the members also have the desire to run away from any predators they may spy, the whole herd will have protection from predators. Herd animals can usually run long and fast, and so as long as they run together, some members of the herd will avoid predation by outrunning any predators they may encounter. This is presumably the function of the herd instinct.

Leadership can make merely “gravitational” social level behavior more functional. Herd animals do not need a leader, because that role can be played by any member that happens to spy the predator first. But leadership can be useful to carnivores in acquiring energy. Wolves, for example, can all reliably attack the same animal, if they have a leader. Leaders are provided by dominance hierarchies. With the right kinds of conditional, instinctive desires, a competition or face-down among members can determine a “pecking order” among the members. The selection of goals for social level animal behavior is then centralized in a leader, and they can prey on animals that would be out of reach for individual animals, not to mention making it possible to settle conflicts among members over food or mates.^xxxvii

Locomotion is about the limit of social level behavior in animal societies, because the other aspects of animal behavior, such as attacking prey and eating, are left up to the individuals acting in parallel. Societies of subjective animals are inherently more powerful than societies of telesensory animals, since they are less dependent on the inheritance of rigid instinctive routines for individual animal behavior. And group level locomotion can be more powerful with a higher level of neurological organization to guide it. Packs of wolves make better use of group level locomotion than flocks of birds, and groups of dolphins can use locomotion for purposes that are beyond schools of fish. But even societies of manipulative animals can only act in parallel with one another. Elephants, for example, may join forces in tearing down a tree, but even if they are manipulative animals, they cannot intentionally fold a tree into some shape like two hands working in different ways to produce a single result.

Need for social coordination. To put it positively, in order for animal societies to have animal behavior at the social level that is analogous to the behavior of even multicellular animals, it must be possible for the members to divide up tasks that work together as whole like different parts of an animal body, such as jaws working against one another to catch prey. This would be especially valuable for groups of hominids in acquiring food, since they cannot run fast enough to prey on herd animals like predatory carnivores. For example, if the group could make some members chase herd animals down a ravine where others were waiting to club them or roll rocks onto them, the group could kill animals that would be out of reach simply by chasing them. It would enable hominids to tap sources of energy that previously were available only by scavenging leftovers from carnivores.

The key to generating animal behavior at the social level is, therefore, coordinating the behavior of the members in a sense that involves a “division of labor” among the members. That would make the animal society more like the body of a subjective animals, for the animal society as a whole could adapt the spatial aspects of its social level behavior to the spatial aspects of the situation, much as different parts of a multicellular body are coordinated by motor commands to act as a whole on other objects in space.

Furthermore, such coordination of the members’ behavior in group action would be even more powerful, if the “motor commands” to different parts of the body were not merely instinctive, nor even discovered by trial and error, but designed in structural imagination to adapt the spatial aspects of social level behavior to the spatial aspects of the current situation, like primates coordinating the movements in different hands to attain a single goal.

Social coordination by the biological behavior guidance system. It is possible for the division of labor among the members on which coordination depends to come from the biological behavior guidance system, because the goals that animals pursue depend on the desires that it builds into them. But the biological behavior guidance system is not much help, because it cannot divide up labor very much, except by crippling social level animal behavior in another way.

In animal societies. It is possible for the biological behavior guidance system to give different members of the same species different desires, because in sexually reproducing multicellular animals, as we have seen, the unit of selection can be the entire family. When the organism going through cycles of reproduction is not just the individual, but the mating pair and its offspring, their behavior can be naturally selected for controlling conditions that affect the reproduction of the whole organism. Males and females can be given different desires.

In some African wolves, for example, the females have the desire to stay in the den and care for their young while the males have desires that lead them to hunt together in a pack, eat their prey, and return to the den and regurgitate food for their families.

More common are mating rituals and elaborate, ritualized fights by which males determine which of them will have access to females.

Likewise, the biological behavior guidance system can give parents and children different desires. We have seen how the peculiar disjointed nature of these “composite organisms” (or composite primary structures) can account for altruism among children and grandchildren.

Age and sex differences do not, however, afford enough division of labor to enable animal societies to act as social level animals. And even if it did, it would not divide up labor differently in different situations, because instincts are shaped only by natural selection of whole biological behavior guidance systems.

The maximum coordination in animal societies provided by the biological behavior guidance system is illustrated, perhaps, by the wild dogs of Africa. It is said that they can herd other animals in certain directions, using barking to coordinate their behavior, so that other dogs waiting for them can ambush the prey as they run by. This improbable geometrical structure in their social level behavior can trap their prey, like the limbs of a single animal body reaching out to pull energy-rich objects into its jaws, even though it is just how the motion and interaction of independent bodies add up in space over time because of the desires that motivate them. This is to add group level ingesting of energy rich object to locomotion in the repertoire of animal societies.

But like all instinctive behavior, it depends on the biological behavior guidance system, and thus, it still cannot be adapted to new situations except by the relatively slow process of biological evolution.

In multisomatic animals. There is one way that the biological behavior guidance system can impose a more complex division of labor. It occurs, as we have seen, in multisomatic organisms, such as insect colonies, where in addition to age and sex differences, members are determined to have different kinds of behavior by the pheromones, or messenger molecules, they encounter.^xxxviii But this mechanism of coordination requires animals to have specific locations in the geometrical structure of the whole organism in order for them to encounter the right pheromones at the right times. The unchanging geometrical structure is provided by a hive or labyrinth of tunnels. The pheromones are distributed to specific locations in the process of setting up the multisomatic organism, and in at least one mammal society as well as many insect colonies, it centers on a queen whose offspring populate the colony.

This possibility is exemplified by the blind mole rat of East Africa. Their reproduction is organized around queen, which is located at the center of a network of tunnels in the ground, and pheromones are distributed among them, determining different members to pursue different goals, by how they eat one another’s feces.

There is, in other words, a structural cause of animal behavior on the social level in multisomatic animals. But it is of no use to animal societies, because they have no unchanging spatial relations among the members. They are merely “gravitational objects” on the social level, sustained by gregarious desires, with the spatial relations among the members continually changing. To acquire a geometrical structure as a whole would constrain the motion and interaction of its members severely, for they would be sedentary and able to act only like moving parts in an otherwise rigid machine.^xxxix

As mere animal societies, therefore, bands of hominids had only a limited capacity to generate social level behavior. The radiation of these primates into the grasslands made them bipedal. They carried clubs and may even have wielded axes to fend off predators that attacked them, including members other families. These traits were inevitable, and adaptation to membership in nomadic bands may account for other hominid traits. Though dominance hierarchies resolved conflicts and provided leadership, the need to remain in proximity to one another strengthened and refined social desires. And being manipulative animals, they could accumulate and pass on useful skills and habits (especially if they had the capacity to imitate one another’s behavior). As skill at wielding clubs increased, other tools were probably added, making it possible to hunt and kill larger game. They may have evolved group level hunting behavior as complex as wild dogs, and their structural imagination may have given them more complex signals for coordinating their behavior. They may even have learned to control fire. And the group level natural selection that nomadic bands imposed on themselves by the scarcity caused by their own population growth may have favored neurological refinements that account for the expansion of the brain. But since those nomadic bands were still just animal societies, hominids encountered the same limit on their power to generate social level behavior as other animal societies.

The original function of natural sentences. Though the evolution of wild dogs and societies made up of other merely subjective animals had to stop, once reproductive causation had made them as powerful as possible, the evolution of hominid society would begin a new stage of evolution, because primate imagination, with its capacity to understand structural causation, made a revolutionary change possible. That change was a new kind of animal behavior guidance system at the social level. But it was unlike the structural causes that had evolved to guide behavior at lower levels of biological organization. It was a primitive language.

Though in animal societies, social level behavior is never anything more than how the animal behavior of members with different desires (and, thus, different intentions or goals) add up in space over time, language is a mechanism that reaches inside each individual’s behavior guiding system and controls its animal system of representation. By connecting all these innermost mechanisms, language can give all the members of the group a single, common intention, and thus, even though they may all be performing different tasks, the group acts on other objects in space as a whole.

The reason that hominid society could evolve into spiritual animals, while other animal societies, such as packs of wolves and herd of ungulates could not, was structural imagination. Language requires a higher level of neurological organization, and it could be tried out as a radical random variation only on hominid brains.

How natural sentences coordinate behavior. Only a primitive language is needed to guide social level behavior. By a “primitive language,” I mean a language with “natural sentences,” that is, sentences with a simple subject-predicate grammar (or subject-verb-objects grammar). Natural sentences can refer to individual members and represent them as behaving in certain ways (or in certain ways in relation to certain other objects in space), and thus, a set of natural sentences, one for each member, can represent a plan for social level behavior by assigning different roles to different members. Here is how it would work.

In the beginning, the leader of the group would imagine a way of coordinating behavior in the situation that seemed to satisfy their desires, and he would assign roles to individuals by using natural sentences, in everyone’ presence, to describe how each member was supposed to behave. That public linguistic interaction would give the members a shared understanding of what every member was supposed to do in advance of acting. That is, each member would know not only what he was supposed to do, but what everyone else was supposed to do. Since members could play complementary roles in a common plan, the society could act as a whole on other objects in space and thereby control relevant conditions that were previously out of reach.

Coordinating behavior was not necessarily as simple as a leader telling each member what to do, because the use of natural sentences depends on imagination, which is a form of understanding by which animals can see what is possible. The manipulative animal system of representation uses images and how they change over time to represent regularities about change that are caused by the motion of objects relative to others and by the manipulation of objects, and since public utterances can control everyone’s imagination, every individual would be able to “see” the difference that each member’s behavior would make. By fitting those individual contributions together in “mammalian space,” each member could see what consequences they would have jointly in the situation thereby understanding how their behavior would attain some goal. The coherence of the plan would be tested in the process of adopting it, because each individual would understand what his own behavior was supposed to contribute to the plan and they would not be as inclined to follow the leader, if the whole plan or their role in it did not make sense to them.

Analogy to the multicellular biological behavior guidance system. There is a useful analogy to the multicellular biological behavior guidance system. The use of natural sentences to coordinate the behavior of individual animals resembles how the multicellular biological behavior guidance system coordinates the behavior of cells in constructing the bodies of multicellular (and multisomatic) animals. In both cases, a copy of the entire plan for the higher level structure is distributed to each lower level organism. Each cell receives a copy of the entire genome by the asexual reproduction of the fertilized egg cell in the process of embryological development, and each member of the spiritual animal receives the same plan of coordinated behavior by public, linguistic interactions in which the leader tells each member what to do. And in neither case will this means of coordination work, unless each member receiving a copy of the plan identifies itself with a different role in the plan, for otherwise it will not be able to generate the special kind of behavior required of it.

In the multicellular biological behavior guidance system, each cell can identify with a certain part of the genetic blueprint for the multicellular body because each cell has a fixed location relative to all the others in the process of embryological development. Different cells are determined to open up different segments of their chromosomes and generate different kinds of behavior by their locations in the geometrical structure of the body as a whole and the messenger molecules received there. (In insect societies, the process of development typically uses a “queen” to produce most of the multicellular members and construct a hive, and different members are determined to behave in different ways by the pheromones located where they find themselves in that structure.)

With the use of natural sentences, an unchanging geometrical structure is not necessary, because the plan is distributed by public linguistic interactions. The members all have animal systems of representation by which they are aware of the locations of one another’s bodies and other objects in the region, and thus, when the leader assigns different roles to different members, not only do the members construct the same plan of behavior relative to the same objects in space in their own faculties of imagination, but the members also identify each member with a certain agent in the plan, including themselves. Thus, different members intend to behave differently when the time comes, but their actions all fit together as a whole.

Contrast to animal signals. Even a primitive language is fundamentally different from the communication used in animal societies. Cries and screams of various sorts are used by other social animals, but such signs do not control imagination in the same way as natural sentences. Signals do enable them to communicate with one another and affect one another’s behavior, but they are inherently incapable of assigning tasks to members of a group.

Wild dogs of Africa use a system of different kinds of barks to coordinate their behavior in herding other animals toward the kill, and honey bees perform a dance by which those returning from a source of energy can indicate its direction and distance to other bees that are just departing. Such animal signals can be versatile, communicating different messages in different situations. As many as sixty different cries have been identified in societies of monkeys, and the hominid mouth and larynx were probably shaped by reproductive causation to generate many more kinds of signals.

But signaling cannot be used to assign tasks to individuals in advance of generating social level behavior, because signals and signs depend for their meaning on the locations of the animals sending and receiving them. Honey bees can communicate the distance and direction to the source of energy, but only because the other bees emerging from the hive already have the goal of traveling to a source of energy and they know to take the directions for locomotion as relative to the hive, the stationary body of the multisomatic organism where the signals are given. Monkey cries are also relative to the location of the signaler, for example, indicating where a certain kind or predator has been detected or where help is needed. Likewise, barking may coordinate the behavior of wild dogs relative to one another so that together they herd other animals in a certain direction, but the goals are fixed and the messages are part of an instinctive pattern that has been shaped to have this effect by reproductive causation.

This dependence of animal signals on the context of their utterance for the communication of their references and meanings makes them useless in assigning different roles to individual members in a plan of social level behavior. In order for animals to use verbal behavior to share a plan that divides up tasks among them, it must be possible, in advance of acting and regardless of its context, to refer to particular members and describe how each is to behave at a later time so that every member can understand who is to behave how and in what situations. That is what the simple grammar of natural sentences makes possible, and since animal communication lacks a grammatical structure, other animals do not have even a primitive language.

Contrast to animal societies. Language makes spiritual animals fundamentally different from animal societies, because the use of natural sentences is a structural cause for social level behavior. Animal societies have no structural cause for their social level behavior. Their social level behavior is simply how the behavior of members with possibly different desires (and, thus, different intentions or goals) add up randomly in space over time. The members act alongside one another, each pursuing its own goal.

The use of natural sentences is, however, a structural cause of social level behavior. Though there are no unchanging spatial relations among the members, they are in more or less continual linguistic interaction, and their linguistic interactions distribute to every member a plan for social level behavior toward some object in space in which each member is assigned a specific task that is designed to fit together with other members so that the group as a whole attain some goal. The result is a form of animal behavior, because it acts on other objects in space. That is, the group as a whole channels the thermodynamic flow of matter toward evenly heat to do work by imposing a geometrical structure on the region in ways that control conditions that affect their reproduction. Their social level behavior is a structural global regularity, and it has a structural cause, even though it is not a simple material structure.

The structural cause is the use of natural sentences, because that is what distributes the same plan of joint action to all the members, including the special instruction that informs each member about his special task. Since the behavior of all the members is represented in the imagination of each member prior to acting, the members of spiritual animals can be said to have the same intention. Instead of pursuing private goals alongside one another, they are all pursuing a single, shared goal. That is the sense in which the spiritual animal itself may be said to intend to behave in the way described by the plan.

That is, the spiritual animal works like a machine. With each member of the group playing a different role in their common plan, each member is like a moving part of an invisible machine whose motion and interaction is constrained by its location in that invisible geometrical structure of the whole machine. But what makes the machine invisible is that its structure as a whole is just the shared plan. The plan requires only that each member be able to imagine how all the participants will move and interact in the situation as a result of exchanging linguistic representations and act accordingly, and thus, the machine's structure is not only invisible, but infinitely flexible.

But since groups of language using primates have no body apart from all the independently moving bodies of its members, the social level animal can be said to have spiritual body. That is the reason for calling it a spiritual animal.

Contrast to multisomatic animals. Multisomatic animals, such as insect colonies, also have social level behavior generated by a structural cause, but it depends on having a physical body at the social level and that makes them less powerful than spiritual animals.

Since the unchanging geometrical structure of the multisomatic body comes from a hive or network of tunnels, their physical body makes them sedentary. However, the spiritual animal is not sedentary. It can move around as a whole and act on other objects in space like a manipulative multicellular animal on the social level of biological organization. It can, in effect, send different motor commands to different parts of its body, except that, with a spiritual body, there is no constraint on how each part can move and interact in relation to one another. It is as if its hands could manipulate objects without arms connecting them to the body.

Furthermore, in multisomatic animals, the coordination of members’ behavior is like an inherited instinctive routine, because it is determined by their biological behavior guidance system. The spiritual animal, on the other hand, has the use of the most highly evolved animal system of representation at the multicellular level to coordinate its behavior. It does not have to wait for instincts to evolve in order to adapt spatial aspects of its behavior to spatial aspects of the situation, as telesensory animals do. As long as the members have a desire to do what the leader instructs them to do, it does not even have to rely on trial and error to shape its social level behavior to fit situations, as subjective animals do, because structural imagination can be used in advance of acting overtly to design social level behavior so that it will control relevant conditions by how it fits together spatially with the other objects in the current situation. Different “motor commands” are sent to different parts of its spiritual body in the linguistic interaction by which the leader explains the plan. Thus, spiritual animals can generate novel, but appropriate kinds of animal behavior in the situation — much as Kohler’s ape did in using a stool and stick to knock down the banana, except on the social level.

Spiritual animals. The evolution of a primitive language marks, therefore, the evolution of a new kind of animal. But it is unique, because, according to this ontological explanation of revolutionary evolution, this stage of evolution has two ontological causes. Like previous stages in the evolution of multicellular animals, one ontological cause is a higher level of neurological organization, because what makes it possible to guide social level animal behavior is the use natural sentences. But since it is also the evolution of an animal at the social level of biological organization, another ontological cause of this revolutionary change is a higher level of biological organization. Being caused by higher levels of part-whole complexity in evolving organisms in two different ways at once is unprecedented in the course of evolution. And it makes what evolves at the first spiritual stage unique is other ways.

Unique kind of essential nature. The use of natural sentences to coordinate behavior in groups of hominids is a new animal behavior guidance system. Indeed, it is the new kind of animal behavior guidance system made possible by the social level of biological organization, just as the nervous system was the new kind of animal behavior guidance system made possible by the multicellular level. And as we shall see, it is only the first stage in the evolution of that animal behavior guidance system.

What makes animal societies so much less powerful than spiritual animals is that they not no behavior guidance system to guide social level animal behavior. They have only the animal behavior guidance systems built into their multicellular bodies, and their social nature, such as it is, comes from desires built into their brains that make them gregarious and, perhaps, set up a dominance hierarchy among them.

Insect colonies and other multisomatic animals do have behavior at the social level that is generated by a behavior guidance system, but it is a biological behavior guidance system, not an animal behavior guidance system. That is, insect colonies are what we called “anomalous animals,” because the only animal behavior guidance systems involved in generating their behavior exist in the lower level parts, the individual insects. Insect colonies are like sponges, except that being on the social level, they are made up of insects, rather than collar flagellates. Thus, they do not have animal behavior at the social level at all. They do not move around in space as a whole, nor do they act on other objects as a whole. Only the parts have animal behavior. Their social level behavior is like that of a plant, acting on the world as a whole or, at most, orienting behavior in an ambient field. In short, multisomatic animals have only a biological behavior guidance system at the social level of biological organization., and even that is only an extension of the multicellular biological behavior guidance system (or the mechanism of embryological development) to construct a multisomatic body on the social level in addition to the bodies it already constructs on the multicellular level.

Social level biological behavior guidance system. Spiritual animals do have animal behavior on the social level guided by an animal behavior guidance system, as we have seen. But the first indication of their unique kind of essential nature is that their animal behavior guidance system is not constructed by a social level biological behavior guidance system. At all previous stages in which animals evolved at a higher level of biological organization, their new kind of animal behavior guidance system required a structural cause that was constructed by their biological behavior guidance system, and thus, the biological behavior guidance system had to evolve first.

Multicellular animals had to evolve a mechanism of embryological development before there were animals with nervous systems on the multicellular level, because that is what constructs their nervous systems.

And in both prokaryotes and eukaryotes, the first behavior guidance system to evolve was a mechanism that could lead them through their reproductive cycles independently of the cycle of night and day. Only later did they evolve the capacity to acquire energy by ingesting other objects in space and the special mechanisms required to choose between incompatible kinds of behavior toward other objects in space, such as whether to ingest them or not. And those animal behavior guidance systems were both constructed and maintained by the capacity of their biological behavior guidance systems to coordinate the behavior of the lower level organisms of which they were composed.

Spiritual animals are, therefore, radically different, because they evolved a behavior guidance system for animal behavior at the social level without first evolving a social level biological behavior guidance system.

The lack of a social level biological behavior guidance system is not so puzzling when we think about them concretely, because we can understand how the use of a primitive language of natural sentences makes it possible to coordinate the members’ behavior in generating social level behavior. That is why I introduced spiritual animals by explaining the function of language in groups of primates. We can see that its evolution is inevitable, if language is possible. However, an ontological explanation of the stages of evolution cannot afford to overlook the curious nature of spiritual animals. The use of language is clearly a social level behavior guidance system, because it guides animal behavior on the social level in groups of primates. But it would be wrong to conclude that spiritual animals have no social level biological behavior guidance system at all.

The truth is that the use of natural sentences is also a biological behavior guidance system at the social level. Spiritual animals also go through cycles of reproduction in which they use free energy to do both kinds of work, the non-reproductive work of controlling relevant conditions as well as reproduction itself, and since they choose for themselves when to grow and when reproduce, they have their own biological behavior guidance system.

Their non-reproductive work is the social level animal behavior that explains why language evolved. The use of language is an animal behavior guidance system, or the structural cause for social level behavior, and animal behavior is a form of non-reproductive work.

The spiritual animal also reproduces as a whole. Indeed, reproduction is easy for spiritual animals, because it is just a matter of the group dividing into smaller groups which go their separate ways. And reproduction becomes necessary from time to time, because the members continue to reproduce on the individual level and spiritual animals eventually become too large to gather enough food for everyone by hunting and gathering by wandering around.

The division of the group can be generated by the instructions of a leader in the same way as other kinds of behavior, and when they divide, the smaller groups have all the same kinds of powers as they parent group. That is, each takes their primitive language with them, and the instinctive desires that lead to a dominance hierarchy gives each daughter group a leader so that it can do the non-reproductive work of acquiring energy and growing.

A new form of life. Since spiritual animals have all the characteristics that led us to believe that prokaryotes were the first living organisms, it seems that they must be considered a new form of life.

What marked the beginning of life, we decided, was the evolution of the first biological behavior guidance system, for that enabled the cells to go through reproductive cycles on their own, independently of the cycle of night and day. Since each cycle included non-reproductive work as well as reproduction, those cells had the kind of autonomous activity that is ordinarily meant by “living.” And we took this ordinary meaning of life to be ontologically significant, because it indicated a change in the ontological cause of evolution. It meant that natural selection was no longer imposed on them from outside, by the circadian cycle. Reproductive causation takes the cause of natural selection to be reproduction, because population growth leads to a scarcity of free energy that requires some reproductive cycles to come to an end. After the evolution of the first biological behavior guidance system, therefore, organisms imposed natural selection on themselves by their own reproduction.

Spiritual animals clearly have autonomous activity in the ordinary sense, for they generate both growth and reproduction on their own. And it has the same ontological significance as it did in prokaryotes, because their social level reproduction does mean that growth in the population of spiritual animals will eventually make resources scarce. They will eventually impose natural selection on themselves, and thus, like other forms of life, they will make themselves evolve. Their social level reproductive cycles will add up in space over time to a gradual change in the direction of maximum holistic power for organisms of their kind, which is natural perfection for organisms of their kind.

Spiritual animals might even be called the “third origin of life.”

Life first evolved when cell enclosed loops of DNA with a regulatory mechanism evolved into a biological behavior guidance system that led prokaryotes through cycles of reproduction independently of the circadian cycle.

But much the same thing happened again when colonies of prokaryotes that constructed aquatic balloons evolved a nucleus and were also able to go through reproductive cycles independently of the cycle of night and day. In both of these cases, life began with the evolution of a structural cause that could take over responsibility for their entire reproductive cycle.

That is also what happened to nomadic groups of primates when they evolved the capacity to use language to guide their social level animal behavior, for that was the evolution of a structural cause that would generate the reproductive cycles by which they would impose natural selection on themselves. Though in this case, the mold for their reproductive cycles was no the cycle of night and day, it was just as inevitable, because they were imposed by the reproduction (and, hence, population growth) of its members. With the evolution of natural sentences, choices about social level growth and reproduction were made by a behavior guidance system.

There is one aspect of spiritual animals that may make us reluctant to think of them as living organisms, though it does not disqualify them in the end. It comes from how spiritual animals are different from multicellular animals. Individual multicellular animals can have minds, but spiritual animals cannot.

By “mind,” I mean not merely a process of guiding animal behavior, but one with the unity of consciousness as well. We have seen how the behavior guiding process that occurs in brains gives rise to a form of matter whose intrinsic essential nature accounts for phenomenal properties, that is, the appearances that subjective animals have in perceiving the world, thinking about it, and feeling desires. (See Stage 6: Subjective animals: Unity of consciousness.)

Spiritual animals cannot be conscious in that sense, apart from the consciousness of its members. Disjointed, composite organisms cannot have neurons working together as in the thalamic projection to the neocortex like a massive complex antenna generating photons that register activity throughout the brain. Spiritual animals do not have conscious minds. But the assumption that such a subjective aspect to experience is essential to life may explain the reluctance to think of spiritual animals as living organisms.

It is not, however, sufficient reasons to deny that spiritual animals are a new form of life, for if it were, we would have to deny that prokaryotes and eukaryotes, plants and telesensory animals are forms of life. They do not have the unity of consciousness. But they are surely alive. Thus, I see no reason to deny that spiritual animal are a new form of life. The fact that they are made up of parts that are themselves living organisms, indeed organisms with the unity of consciousness, does not mean that they are not alive. It only points up how spiritual animals are unique in the course of evolution.

Lack of a social level material structure. What makes spiritual animals different from the evolution of life in prokaryotes and eukaryotes is that spiritual animals do not have any unchanging structure on their level of biological organization, except the more or less continual linguistic interaction among its members.

The members must continually interact linguistically, for that is what coordinates their behavior as parts of a higher level organism. But since the continual exchange of linguistic representations is the only unchanging geometrical structure that is required at the social level for the use of language to guide the behavior of the spiritual animal, it is provided by their gregariousness, which is due to the biological behavior guidance system of each individual member.

This is the reason for calling the new kind of animal at the social level of biological organization “spiritual” animals. The spiritual animal has no body of its own, except the bodies of all its members, and since a form of life that does not have a physical body is the traditional meaning of “spiritual,” it is appropriate to call these groups of language using primates “spiritual animals.”

Having a spiritual nature gives spiritual animals a great advantage when it comes to the efficiency of reproductive causation, because it means that natural selection is at work simultaneously on two different levels of biological organization. At the same time that the reproduction of spiritual animal at the social level is causing a population growth that imposes natural selection at the social level, the sexual reproduction of its members is causing a population growth within spiritual animals that imposes natural selection at the individual level. Simultaneously on two levels of biological organization, therefore, there is a gradual change in animals in the direction of natural perfection for organisms of their kind. As spiritual animals become as powerful as possible for animals made up of language using multicellular animals as parts, their members become as powerful as possible for animals that exist as parts of spiritual animals.

What makes this two-level gradual evolution possible is having a spiritual nature, because that makes social level reproduction easy. The members of a spiritual animal move around in space separately from one another, and so reproduction at the social level is merely a matter of subgroups separating from one another and going off in different directions, terminating their linguistic interactions with one another. That is what makes it so easy for language to serve as a biological behavior guidance system, given that it has the capacity to guide social level animal behavior.

The evolution of eukaryotic cells is analogous to the evolution of spiritual animals, except that eukaryotes have a material structure, or physical nature, rather than spiritual nature. The behavior of the lower level organisms is coordinated by enclosing them all within a cell, and thus, reproduction depends on dividing the cell and all reproducing all the lower level organisms of which it is composed. And since there are two lower levels of structural causes contained within the eukaryotic cell (the prokaryote-level chromosomes and the RNA-level genes of which chromosomes are composed), eukaryotes have a very complex structure, which taxes the capacity of reproductive causation to change in the direction of natural perfection. As evolving structures become complex, more random variations are possible, and eventually there is not enough time to try them all out. Their star will die first. Eukaryotes overcome this obstacle, as we have seen, by sexual reproduction. Sexually mixing their lower level structural causes as part of the process of reproduction focuses natural selection on those parts whose contribution to the whole makes the biggest difference to their power to control relevant at that point in their gradual evolution. Thus, instead of evolving by simple branching, like prokaryotes, eukaryotes can evolve as a species with a gene pool. And favorable random variations that occur in different members of previous generations can accumulate in individuals of later generations.

The advantage of having a spiritual nature is that no such special mechanism is required to focus natural selection on the lower level structural causes of which they are composed. Or rather, the way in which members mate outside their own group and migrate from one group to another means that a kind of “sexual mixing” is constantly going on in spiritual animals. Nor does the evolution of the parts depend on group level natural selection. Natural selection works to some extent on individuals within spiritual animal, because there are still conditions to be controlled within spiritual animals that affect their reproduction, and those who are better able to control them tend to leave more offspring.

The way that spiritual animals differ from organisms with a material structure makes them seem like what we called “composite organisms,” but they are something more.

We recognized the existence of composite organisms in discussing what is the “unit of selection” according to reproductive causation. We have seen how mating pairs and families are organisms that impose natural selection on themselves by their own reproduction and make themselves evolve. Even nomadic bands of hominids were composite organisms of a kind, since they were subject to group level selection. We called them composite organisms, because what goes through those reproductive cycles is not a material structure (with an unchanging geometrical structure), but a collection of material organisms.

Individual organisms are different from composite organisms because each originates from a single fertilized egg cell and they cannot be divided up without dying. Composite organisms are “dividual,” rather than individual, organisms. Though they can die, they do not necessarily die when they are divided up.

Spiritual animals are composite organisms by this test. They evolve by going through reproductive cycles and imposing natural selection on themselves at the social level. And they are “dividual,” because they do not necessarily die when they are broken up. Indeed, that is how they reproduce. But they are not merely composite organisms. Even though they do not have a material structure as a whole, they do have a structural cause of their social level animal behavior. It is a spiritual structural cause, and that is what is unique about spiritual animals.

Social and cultural aspects of the spiritual structural cause. Spiritual animals have a unique kind of essential nature, therefore, because the ontological cause of their social level behavior is a spiritual structural cause, rather than a material structural cause (or material structure). The spiritual animal is the new kind of animal that is made possible at the social level of biological organization stands, but it stands in stark contrast to all previous animal. Though it has biological and animal behavior at the social level, it does not have any unchanging geometrical structure at the social level to serve as its structural cause — except for the continual linguistic interaction of its members. That is, the use of language to coordinate the members’ behavior is its structural cause.

The spiritual animal has no body of its own, because with the use of language, it does not need a body to have a structural cause to serve as its behavior guidance system. Its only body is all the bodies of its members, which are in more or less continual linguistic interaction with one another. That is what earns the spiritual animals its name.

Since a form of life without a body is what has traditionally been meant by “spiritual,” “spiritual animal” is the appropriate name for the kind of organism that evolves from manipulative animals, that is, at the eight stage of evolution.

The use of language as a structural cause to guide social level behavior gives spiritual animals an essential nature that includes two kinds of structures, and it should be noticed at the outset, because it will play an important role in explaining the evolution of spiritual animals.

The use of language, as we have seen, is both a biological and an animal behavior guidance system for spiritual animals. It is able to serve both functions, because it generates social level behavior by coordinating the behavior of its individual members. That is, it does not need any material structure at the social level to serve as a structural cause for its social level animal behavior. But it does need the continual linguistic interaction among the members, and in that mechanism, there are two, fundamentally different kinds of structures, involving two fundamentally different kinds of part-whole complexity, which are essential to their spiritual nature.

The evolution of spiritual animals involves, as we have seen, higher levels of part-whole complexity in both ways that have been traced in this ontological derivation of the overall course of evolution in a spatiomaterial world: a higher level of neurological organization as well as a higher level of biological organization. Language has a nature that makes it essential to both.

The capacity to use language is the function of the higher level of neurological organization in the individual members, for, as we shall see, it a new way of manipulating “object images” in the “local image” and constructing “maps” of such “local images.”

But linguistic representations are not just constructs in imagination. They can be generated publicly by speaking, and their public manifestation is what makes it possible for them to coordinate the behavior of many different multicellular animals as parts of a higher level organism. Thus, this other aspect of language, its being public, is also essential to the nature of the spiritual animal.

Language is, therefore, what ties these two higher levels of part-whole complexity together as a single object in space with a new kind of essential nature, and that means that spiritual animals have two fundamentally different kinds of structures as a whole. In other words, the essential nature of the spiritual animal is uniquely twofold.

All the organisms and structures whose evolution we have traced thus far, including not only biological organisms and neurological structures, but also behavioral schemata, have essential natures that are defined by a single, material structure. I have called them “organisms,” or “reproducing organisms,” but they all involve a single way in which material parts are bundled together so that they go through reproductive cycles as a whole and impose natural selection on themselves.

But in the case of case of spiritual animals, two structures define their essential nature: how multicellular animals are combined as parts of a social level organism and how words are combined as parts of the sentences that they can all generate as public behavior. Both are aspects of the “organisms” that go through reproductive cycles and impose natural selection on themselves by their own population growth.

The structure that spiritual animals have because of their higher level of biological organization will be called the “social aspect” of spiritual animals, and the structure that spiritual animals have because of their higher level of neurological organization and the linguistic representations that they exchange will be called the “cultural aspect” of spiritual animals.

Social aspect. The social aspect is a structure of the spiritual animal as a whole in the same way as each higher level of biological organization involves a new structure. Lower level organisms are bundled together as parts of a higher level organism by coordinating their behavior. In the case of spiritual animals, they are bundled together in a way that does not require a specific set of spatial relations among them. But being in continual linguistic interaction is nevertheless a kind of structure, for it makes them all parts of a higher level organism. And as we shall see, that kind of structure is the source of its greater power as an animal and, later, makes it possible to for additional social structures to evolve because they generate social level behavior that controls some condition that affects the reproduction of spiritual animals.

Cultural aspect. The cultural aspect is also a structure of the spiritual animal as a whole, because what makes it possible for linguistic interactions to guide the behavior of the spiritual animal as a whole is that all the members speak the same language. The structure of language is a structure of the whole because it is a structure that is contained in each member of the spiritual animal. Its being located in each member is what makes it possible for one and the same structure to serve as both the biological animal behavior guidance system for the spiritual animal. The spiritual animal does not need a biological behavior guidance system that can set up a complex structure to function as an animal behavior guidance system, because that mechanism is contained in each of the parts and all that is necessary for it to generate group level behavior is that the members continually interact with one another linguistically. The cultural structure is potentially complete in each individual brain, and calling the linguistic structure “culture” anticipates somewhat the significance of this aspect. Not only are the two subsequent stages of evolution caused by higher level of part-whole complexity in linguistic representations exchanged as culture (that is, higher levels of neurological organization), but culture is itself capable of evolving by reproductive causation. That is the main source of increases in the power of spiritual animal to control relevant conditions.

The possibility of linguistic level of neurological organization. In order to show the inevitability of spiritual animals in the course of evolution, however, it is necessary to show not only that language is functional and can control relevant conditions that were out of reach for animal societies, but also that language is possible. From its function, we can tell that language must involve some form of overt individual behavior that others can observe and that it must be able to reach deep into their brains and control their imagination. The overt linguistic behavior must be able, therefore, to convey what the speaker is imagining so that the perception of that behavior by others causes the same content to occur in their imaginations. The overt behavior must, in other words, be a representation of the content of imagination.

As we have seen, however, such representations would have to be more complex than the signs used by other animals. Animals use cries and screams as signals to communicate with one another, and though they can be quite varied, they are inherently incapable of assigning tasks to members of a group. Their meanings and references depend on the context of their utterance, and that makes them useless in assigning different roles to individual members in a plan of social level behavior. In order for animals to use verbal behavior to share a plan that divides up tasks among them, it must be possible, in advance of acting and regardless of its context, to refer to particular members and describe how each is to behave at a later time so that every member can understand who is to behave how and in what situations.

In order for cries and screams to distribute the same plan of social level behavior to all the members, they must become organized with a subject-predicate grammar. At least two elements must be combined in each linguistic act, for it must connect an individual member with a specific way of behaving without relying on the context to identify either element. Hominids could associate particular cries with different members or other objects and different ways of behaving or other properties, but such signs must be combined in a certain way to serve as representations of a plan for their behavior in some situation. This is the function of predication, that is, taking certain signs to represent the objects and other signs to modify them in some way. But little more than predication would be needed, since the listeners can retain one instruction after another in memory and combine them all as parts of a single representation of the plan, and a series of such instructions would give every member an understanding of the whole plan. But if they had the capacity to communicate verbally how they were combining signs as subjects and predicates at all, it would be possible to complicate such utterances so that they also indicate the other objects and individuals to which the behavior is supposed to be directed, where it is supposed to occur, when, under what conditions, and the like.

The complexity of the behavioral schemata required for a primitive language can be estimated from the grammar of natural sentences in our own language. Even in sentences with a simple subject-predicate grammar, predicates are often themselves rather complex, with a verb and its objects to indicate how the action is directed at other objects in the world. (For example, if behavior is to be directed toward an object in space, the predicate will be a verb that takes a noun as its grammatical object, for example, “picking up a certain ax” or “going to a certain location”.) And complexity increases as these basic elements are modified by adjectives, adverbs, phrases and clauses, as would be needed to make clear what the individual is supposed to do. For example, “Pick up the sharp ax carefully and put in where the tools are kept.”

Repeated and varied uses of the basic mechanism of predication within single utterances may explain how all these elements can be included in natural sentences, but only if there is some way for listeners to tell how the speaker is combining them, for listeners must be able to construct the same representation in their imagination as the speaker’s. There is an asymmetry about the grammatical subject and predicate, and not only must it be clear from what the speaker says which sounds are to be treated as subjects and which as predicates, but it must be clear in each of the other phrases, clauses and modifiers based on predication. In other words, the cries and screams must be made with grammatical markers indicating how their meanings are to be combined in the listener’s imagination.

The linguistic system of representation. Considering the enormous range of possible natural sentences in our language, even a primitive language, based on a simple subject-predicate grammar, may seem too complex to be tried out as a random variations during the evolution of hominid societies. Unless there is some simple way in which the capacity for grammar could be acquired, it will not be clear that the evolution of language is inevitable, and it will not be plausible to hold that the our capacity for language is the result of a long series of accidental selection pressures that would probably not occur on other planets.

There is, however, a basically simple mechanism that could be tired out as a random variation on the primate brain, and it would account for such a primitive language. It is possible, because primates had evolved a faculty of imagination that included both spatial and structural imagination. The ability to use of language comes from the evolution of a linguistic system of representation.

The linguistic system of representation is different from the animal system of representation, because its representations can exist as public objects, that is, as sentences that are generated by overt verbal behavior.

But such a linguistic system of representation is possible only because it is constructed out of parts supplied by the animal system of representation. The manipulative animal system of representation already has a faculty of imagination (both spatial and structural imagination), and the ability to speak and understand linguistic representations comes from a higher level of neurological organization within the faculty of imagination of the animal system of representation. (That is, linguistic behavioral schemata are on a higher level of organization than locomotor and manipulative behavioral schemata, and the images on which covert behavior operates in the sensory input system are naturalistic images, which are compounds of local images and object images)

This new mechanism in the faculty of imagination would account for the “deep grammar” of “universal grammar” that Chomsky identified beneath the surface grammar of all natural languages. Chomsky argued that the remarkable capacity of humans to learn a language, including the ability to generate an indefinitely large range of sentences permitted in it, is best explained by a genetically inherited capacity, could not be explained as a result of operant conditioning (as B. F. Skinner had insisted). The surface grammar of a natural language is, as we shall see, simply the conventions by which the speaker indicates the kinds of covert behavior he is using to construct some representation in his faculty of imagination so that the listener can construct the same representation in theirs. What is universal, in other words, is a faculty of naturalistic imagination.

This explanation might also confirm a more controversial aspect of Chomsky’s position. Chomsky has puzzled many of his followers by expressing doubts about whether this genetically inherited capacity can be explained by Darwinian natural selection. What is bothering Chomsky may be the assumption of contemporary Darwinists that the details of this brain mechanism must be explained as an accumulation of traits a series of caused by a series of externally imposed special selection pressures. But it is not necessary to accept accidentalism to explain the evolution of language. The capacity for language could be another of the more revolutionary episodes in the course of evolution that are not recognized by contemporary Darwinists. If it is provided by a higher level of neurological organization, the advent of language would mark the beginning of a new evolutionary stage. Like all such radical random variations, it would start off simple, uniform and weak, and as a result of reproductive causation, the capacity for language would gradually become more complex, diverse and powerful. And as we shall see, one stage leads to another such revolutionary episode in which a yet higher level of neurological organization makes it possible to use psychological sentences and leads to reason.

What makes it possible for something as simple as a higher level of neurological organization in the faculty of imagination to account for language is the way that imagination is a foundation for the kind of learning that has been explained as a contained form of reproductive causation that takes place during a late phase of embryological development.

The trait that needs to be explained, as Chomsky insisted, is the remarkable capacity of individuals to learn natural languages of vastly different kinds, and that is explained as the evolution of behavioral schemata for generating covert linguistic behavior within the faculty of imagination in each individual brain by a form of natural selection that depends on reinforcement. (Skinner was not entirely wrong to think that operant conditioning was involved.)

The higher level of part-whole complexity in covert behavior marks them a linguistic schemata. But just as neurological development internalized spatial causation as spatial imagination and structural causation as structural imagination, so this contained form of reproductive causation internalizes the natural language used by the spiritual animal in the developing brains of its new members.

And as a byproduct, it gives language users a faculty of naturalistic imagination by which they can think about state of affairs in the natural world and understand efficient cause explanations. That is, they can see states of objects in space against the background of what is possible by efficient causation, either their possible causes or possible effects.

Verbal and nonverbal sides of linguistic representations. The basic social function of language is to represent in public behavior a certain kind of image that is constructed privately in each faculty of imagination. The (potentially) public part of linguistic behavior will be called “verbal behavior,” the words and sentences that can be spoken. But since the images in imagination are a form of representation based on the animal system of representation, the verbal behavior involved is actually just a re-representation of some kind of higher level animal representation.

The linguistic representation has, therefore, both a verbal and a nonverbal side. To show how it is possible for the verbal side, that is, overt verbal behavior, to represent the nonverbal side (or nonverbal covert linguistic behavior and the naturalistic images on which it operates as a higher level animal representation), I will consider how naturalistic images can be constructed in the faculty of imagination and then show how the nonverbal covert linguistic behavior involved in doing so can be represented publicly in overt verbal behavior. I will begin by focusing on how language is handled in the brain of the speaker and then expand on how it works in the brains of listeners who can understand overt verbal behavior.

Let us assume that the mouth and larynx are able to form the broad range of sounds needed for language, though that capacity is undoubtedly among the traits that evolved gradually during the primitive spiritual stage. We can also assume that hominids had the capacity to associate specific (complex) sounds with particular local scenes, particular objects in space, kinds of objects, and ways of behaving as their meanings, since this is a capacity that chimps have. Though that is not enough to explain how words and meanings are connected in the linguistic brain, it does allow us to see how language could evolve in the primate brain. It means that hominids could call up appropriate images in imagination when they heard certain sounds, or make those sounds when the images occurred to them.

The basic mechanism that needs to be explained is the subject-predicate grammar of verbal behavior, and its function can be explained by the meaning that is supposed to be conveyed by it. That meaning is the nonverbal side of the linguistic representation, and since it is a higher level naturalistic image that can be constructed in the erstwhile primate faculty of imagination, let us begin by recalling what is involved in spatial and structural imagination.

Local images are the telesensory images combined (according to input about the bodily condition) as a representation of the local scene relative to the animal’s body. Spatial imagination is the capacity to understand the effects of motion on the relations of objects in the territory by calling up sequences of local images by covert locomotion as well as the effects of motion in the local scene by calling up changes in the telesensory images of which it is composed. Thus, if words (as distinctive sounds) can be associated with such images at all, they can refer to (and re-identify) particular locations by way of local images and to particular objects in space by way of telesensory images in the local images. They can also refer to kinds of objects, or properties, insofar as those kinds can be recognized by telesensory images, including ways in which bodies behave. And they can refer to spatial relations among objects by way of the understanding of the structure of space through spatial imagination.

Because of structural imagination, however, objects in a local scene can also be represented by object images, which are sequences of telesensory images that can be called up from memory by covert manipulation that represent what happens to the object when it is manipulated in various ways. Object images can also be the meanings represented by words, enabling the words to refer not only to particular objects, but also to kinds of objects.

Suppose the leader devising a plan of social level behavior wanted some members to chase deer into a ravine and other members to roll rocks down on them as the deer ran by. He would think about members of the first group by calling up object images of them in his imagination by covert behavior, connecting those images with the (perceived or imagined) local image to represent them as being located in the field outside the ravine where deer are grazing. He would then call up another object image, this time of bodies running and yelling, and his covert linguistic manipulation would combine this second object image with object images of the members in the field, orienting their running and yelling in certain directions relative to the deer. Such combinations of local images and object images would create naturalistic images, or representations of objects in space as being related, moving or interacting with one another in such ways. The structure of imagination together with memory would supply sequences of images representing the changes that can occur, given the naturalistic states being picked out, and thus, the leader would, for example, have images of deer locomotion in response to the images of disturbances being caused. He could anticipate where the deer would run, and so on, allowing him to see what would happen as a means to his goal.

It is, however, one thing to think a plan and another to communicate it, and the latter requires the leader’s verbal behavior to enable others to construct the same plan in their imaginations. Even if the leader had words associated with the local images and with the object images of the members, the deer, and the behavior of chasing, that would not suffice to represent the animal representation he has constructed by his nonverbal (covert) behavior, for the listener must combine the meanings called up from memory by each word in the same way and there would be no way to tell how to do that.

References to the field in the local scene and the particular deer could, perhaps, be conveyed by pointing to them and using such words as “deer” and “field”, because pointing is public behavior and that would enable listeners to could construct representations of those objects in the local scene as objects of such kinds. But the leader could not communicate his plan for social level behavior unless his verbal behavior could control their imaginations so that they combined object images of the members being assigned the task with object images of the task being assigned to them. That is the function of grammar.

If there were a mechanism that would make the leader utter the words in a way that indicated which meanings were to be treated as grammatical subjects and which were to be treated as predicates, the listeners would be able to combine their own object and local images in the correct way. They would call up local images for the words referring to locations and an object image for each member named, and they would combine those object images with images for the kinds of behavior named, so that the listeners would also have a naturalistic image representing each member as behaving in a certain way.

In this case, however, at least three object images would be involved each naturalistic image, because members are supposed to chase the deer. Two of the object images would be treated grammatically as subjects of predication (the member and the deer) and one object image treated as a predicate (the relation of chasing), and all three would be combined in a certain order (together with local images for any references to locations) as a single naturalistic image.

Speaking: nonverbal behavior determining verbal behavior. The nonverbal (always covert) part of linguistic behavior — combining image with another as a naturalistic image of some state of objects in space (or event involving them) — may require some special mechanisms to handle the grammatical subject differently from the predicate, but it surely requires only a minor modification of primate imagination. Chimps that learn to associate words with certain kinds of objects spontaneously combine different words for the same object as a single new word, and thus, it is just a matter of evolving a behavioral schema that keeps the covert locomotion and manipulations straight. The key to the use of language is, therefore, the mechanism that makes the verbal side of linguistic behavior indicate how the images associated with the words are to be combined as a naturalistic image representing some naturalistic state of affairs.

Such naturalistic images are already a higher level of neurological organization on the nonverbal side of linguistic behavior, because it is a new way of “manipulating” object images. Instead of covert manipulations that call up sequences of telesensory images representing the effects of rotating the object, bending it, or putting objects with different geometrical structures together, covert linguistic manipulation combines different images as representations of the same object in the local image at the same time.

The nonverbal side of linguistic behavior may start with one object image for the object in the scene (the grammatical subject) and superimpose another object image (for a kind of object or way of behaving) on the same object in the scene. The result would depend on the object images, but since both meanings are various sequences of telesensory images, it would involve a sequence of telesensory images that depends on some sequence of images from both meanings. That sequence of images would be a naturalistic image, the potential meaning of a sentence or what is called a “naturalistic proposition.”

The naturalistic image could then be used as the grammatical subject to which further object images are added in a similar way (compounding predication within a sentence), or it could be joined in the local image by object images representing other objects in the local scene (conjoining different sentences as a description of the scene).

Such nonverbal covert behavior would require linguistic behavioral schemata with a higher level of part-whole complexity, but that is not all that is required by this higher level of neurological organization, because verbal behavior must also represent how the object images are to be combined. That is, verbal behavior must indicate two things at once, both the images involved and how they are to be combined as naturalistic images. Words for all the images involved must be uttered as part of a single speech act, called a sentence, and the kind of covert manipulation involved must modify the words in some distinctive way, by their order, inflection, prefixes, suffixes, or the like in the sentence.

The capacity to generate verbal behavior of this kind requires a new brain mechanism that does two things: it must connect each image (or “meaning”) involved in the nonverbal linguistic act with its name, and it must register which images are subjects and which are predicates in its construction of the naturalistic image(s) (or “meaning of sentence’). The output of such a center would be able to determine motor commands for verbal behavior that would indicate both aspects of the nonverbal side of the linguistic act.

Understanding: verbal behavior determining (effects of) nonverbal behavior. Linguistic interaction requires listeners who can understand the verbal behavior in the sense of constructing the same naturalistic images in their own faculties of imagination. This would require the new neural mechanism for verbal behavior to work in reverse. That is, instead of using input about the images and covert manipulation of them to generate verbal behavior for words with grammatical markers, it would have to use telesensory input of words and grammatical markers uttered by other to call up the images and combine them in imagination in the indicated way. That would be to construct the speaker’s naturalistic image, or proposition, in the listener’s faculty of imagination.

The structure of the linguistic brain. The evolution of the use of language involves changes that are located in only one of the two hemispheres of the forebrain. It is usually the right hemisphere that continues to serve spatial and structural imagination, which means that bodily behavior, including locomotion and manipulation, can continue to be generated with at least as much skill as primates. The left hemisphere evolves a higher level of neurological organization which is dedicated to linguistic behavior, both the verbal and nonverbal sides. Nonverbal linguistic behavior is a form of covert behavior that manipulates multiple local and object images to construct naturalistic images. They are the meanings of natural sentences, and there are special mechanisms in the left hemisphere for representing this nonverbal behavior verbally (labeled “Wernicke’s area” and “Broca’s area” in the functional diagram of the linguistic animal behavior guidance system). How this higher level is related to spatial and structural imagination is suggested by the functional diagram of subsystems in the linguistic animal behavior guidance system.

This diagram suppresses the arrows between the sensory input and behavioral output systems representing the basic connections that stem from the telesensory animal behavior guidance system (perception and the input to the local image about the current bodily condition). They are crucial to the mechanism for speaking sentences and hearing them as sounds, but they are not crucial to generating linguistic acts or understanding their meanings.

The higher level of neurological organization that constitutes naturalistic imagination occurs in both the behavioral output system and the sensory input system, repeating the kinds of changes that occurred in the evolution of structural from spatial imagination. But in this case, the new structure does not occur within the local image. Nor does it occur within the object image. It is, rather, a structure that includes both of them as parts, namely, the naturalistic image, which is the meaning of the natural sentence. (See the functional diagram of the linguistic animal behavior guidance system.)

In the behavioral output system, the higher level of organization is a kind of behavioral schemata used by the behavior generator that can linguistically manipulate images of all kind, including both local images and object images, in order to construct a compound representation in the sensory input system, the naturalistic image.

The naturalistic image is located in the sensory input system (mainly in a region of the inferior parietal lobe). The covert nonverbal linguistic behavior acts on this region in the same way as spatial and structural imagination (by way of the projection from the anterior to the posterior cingulate gyrus and the latter’s connections with the adjoining areas of non-cingulate neocortex).

Once again, the linguistic behavioral schemata used by the behavior guidance system are actually structure contained in the frontal neocortex, and it has access to them by way of a complete circuit (through the neocortex, corpus striatum and ventral anterior thalamus) which is not depicted in this diagram. This is at least one place where the structures internalized by the evolution of behavior schemata by reinforcement selection are contained.

From the function of language and the nature of the primate faculty of imagination, we have inferred the brain systems that are required for the kind of linguistic act that would enable a leader to distribute a plan of social level behavior to the members of a nomadic band. In addition to the higher level of neurological organization in the faculty of imagination, which make it possible for linguistic behavioral schemata to manipulate images of various kinds as the meanings of words used in constructing the meanings of natural sentences, the use of language requires changes in the nervous system set up by embryological development in order to generate the verbal side of linguistic acts and to recognize their meanings from telesensory images of another’s verbal behavior. They are the regions of the neocortex called Wernicke’s area and Broca’s area in the linguistic hemisphere of the brain.

Wernicke’s area has two different functions, translating the verbal behavior of other speakers that is registered as telesensory input into the naturalistic images that are their meanings, and translating the naturalistic images constructed by the speaker’s nonverbal linguistic behavior into words and grammatical markers so that they can be generated as the verbal side of linguistic behavior.

There is a major connection between Wernicke’s and Broca’s areas not represented in this functional diagram by which Wernicke’s area identifies the words and grammatical markers to be generated so that Broca’s area can, as part of the complete linguistic act, generate the motor commands for speaking the natural sentence.

The connections between Wernicke’s and Broca’s areas, as well as between them and the faculty of naturalistic imagination, can be seen better in the diagram of the linguistic brain. This diagram is looking down on the two hemispheres of the brain, with the linguistic mechanisms located in the left brain. The blue lines depict the causal connections involved in speaking, whereas the red lines in the left hemisphere depict the causal connections involved in listening and understanding sentences spoken by others.

Wernicke’s and Broca’s areas in the left hemisphere are known to play a central role in language, and the roles they have, as indicated by the effects of damage to each, suggest that they work together to serve the function required by this explanation of how language is possible. The verbal aspects of linguistic behavior are handled by Wernicke’s and Broca’s areas of the left (linguistic) hemisphere.

Wernicke’s area is located in a posterior region of the superior temporal neocortex, and damage to this area is known to make patients unable to connect words and their meanings. Given the meanings (or object images), such patients cannot call up their names, and given the words, they cannot identify their meanings.

Broca’s area is located in the frontal neocortex just anterior to the motor neocortex sending motor commands to the mouth, larynx, tongue, and lips, and damage to Broca’s area is known to make patients unable to arrange words with their grammatical markers as well formed sentences, though they continue to be able to understand sentences and suffer only limited loss of ability to produce the words for object images (meanings).

These two areas are connected by the arcuate fasciculus, a large bundle of association fibers that also connections the inferior parietal neocortex to the frontal cortex. It apparently transfers information from Wernicke’s area to Broca’s area, because the effect of cutting it is basically the same as damage to Broca’s area.

Speaking. Wernicke’s area has the function of connecting the verbal and nonverbal sides of linguistic acts. The speech act is generated by a linguistic behavioral schema in the frontal neocortex (as part of the behavior generator). It generates covert nonverbal manipulation in the anterior cingulate gyrus, and (by way of its projection to the posterior cingulate gyrus and the latter’s connections with the inferior parietal area), it constructs a naturalistic image in the sensory input system. The inferior parietal area, where the naturalistic image is constructed, has two way connections with Wernicke’s area, and so it can informs Wernicke’s area about how the naturalistic image is being constructed in naturalistic imagination. Wernicke’s area not only connects the various images with their names, but also registers how the words are being related to one another as grammatical subjects and predicates in each naturalistic image. Wernicke’s projection to Broca’s area provides all the information needed to generate the motor commands for verbal behavior, using the words with proper grammatical markers. The projection from Broca’s area to the part of the overt body image sending motor commands to the mouth, etc., would enable it to generate overt verbal behavior directly. Verbal behavior is, therefore, a result of an act of nonverbal imagination, though the behavior generator (with its linguistic schemata) in the frontal cortex could help Broca’s determine the actual surface grammar used in verbal behavior, when there are alternative ways of marking the words grammatically.

Understanding. Wernicke’s area also connects the verbal and nonverbal sides of the linguistic act in the listener’s brain. The location of Wernicke’s area next to the auditory analysis region of neocortex in the superior temporal lobe makes it easy to receive input about which words and which grammatical markers are identified in the auditory telesensory images caused by another speaker’s verbal behavior, and thus, with its two way connections to the inferior parietal neocortex, Wernicke’s area plays the role of the posterior cingulate gyrus in constructing the naturalistic image. That is, it acts as covert nonverbal behavior, except that it is reaching into the brain to control imagination by way of the public linguistic interaction. The meaning of the sentence is the naturalistic image, which is projected to the behavioral output system (by way of the caudate nucleus, globus pallidus, and the ventral anterior nucleus of the thalamus), so that it becomes part of the local scene in which the subject responds.

Since Broca’s area is not involved in understanding the meaning of a sentence (the proposition), that would explain why damage to Broca’s area does not affect language comprehension. The ability of such patients to name objects (that is, to generate the right word in for each object) is affected, but not completely impaired by damage to Broca’s area. On this account, naming could be explained as repeating sounds heard in auditory imagination. Wernicke’s area would still connect the image and with the word, and so a reverse connection back to the auditory area would provide a telesensory image of the spoken word, enabling the patient to repeat the word without any help from Broca’s area..

Understanding a sentence heard would not require any covert nonverbal manipulation. (But it would be possible for the listener to reconstruct the naturalistic image in his imagination by repeating the sentence to himself, since the behavioral schema for the nonverbal manipulation to generate the sentence would probably be connected in memory with the verbal behavior in speaking it.)

Though understanding linguistic representations does not necessarily involve any covert nonverbal manipulation, language learning still depends on acquiring linguistic behavior schemata for speaking, including covert nonverbal manipulation, because the connections in Wernicke’s area between object images and words and between linguistic manipulations of them and grammatical markers are acquired as part of those linguistic behavior schemata (along with the capacity to generate the right motor commands for the verbal side of the speech act). Without learning to speak, memory might not even contain the images that are to be combined in the naturalistic image.

Understanding sentences would require additional learning, because Wernicke’s area must be able to use telesensory images of the words and grammatical markers used by others to call up the images and control how they are combined in the naturalistic image. However, such learning would be all but automatic, because in learning to generate the verbal behavior, one also hears it, and two way connections between Wernicke’s area and the local and object images would be established by the memory circuit.

The higher level of neurological organization required for language does not come, therefore, from the bilateral specialization of the two hemispheres of the brain. The higher level occurs in only one hemisphere of the brain. The higher level is the higher level of behavior schemata required for linguistic manipulations of object images and the higher level of organization in the naturalistic image itself, though perhaps the addition of Wernicke’s and Broca’s area for representing such covert nonverbal linguistic behavior as verbal behavior might also be considered evidence of a higher level of organization.

The specialization of one hemisphere for language has other functions. It leaves one hemisphere of the brain unencumbered with the mechanisms required for speaking. That also makes it easier for animals to talk and do other things at the same time, even though both activities require the involvement of imagination.

Furthermore, special desires must be attached to linguistic representations in order for the desire to submit to a leader to cause member to do what is described by the leader’s verbal behavior. Thus, if those desires affected the goal selection of the linguistic hemisphere, behavioral schemata for such social behavior could evolve in that hemisphere, while behavioral schemata for satisfying other desires could continue to evolve in the other hemisphere. This requires, of course, that the linguistic hemisphere be the dominant hemisphere, for otherwise the use of language could not reliable control behavior.

There are, of course, many details about how neural connections are made in order to serve these general functions, but this evidence about the structure of the human brain is sufficient for our purposes. I have described a kind of higher level of organization in brain mechanisms that would give primates the use of a primitive language of natural sentences, and since it is within the range of random variations tried out by hominid brains, I conclude that the evolution of language using primates is inevitable. As we expect from this ontological argument, there are such mechanisms in human brains. Learning a natural language can be explained as a contained form of reproductive causation, that is, a neurological development in which linguistic behavioral schemata evolve by reinforcement selection toward maximum holist power, controlling relevant conditions in all the situations where linguistic interaction are useful at all.

Naturalistic imagination. With the evolution of the capacity to use natural sentences, subjective animal evolve a faculty of naturalistic imagination, and like each earlier stage in the evolution of imagination, it gives the animal the conception of something in the world that it could not previously think about explicitly. It is the conception of a state of affairs in the natural world, that is, the state of object in space and how they change over time. With naturalistic imagination, subjects always think about actual states of affairs against the background of what other states of affairs are possible. The possible in this case is the kind of events that can cause or be caused by the state of affairs, and so it gives them an understanding of efficient causation.

Naturalistic imagination does not replace earlier forms of imagination, but is, rather, based on them and incorporates what they understand as part of it own understanding.

Animal behavior necessarily acts on objects in space, and with the evolution of telesensory animals, there is already a conception of the object, because there is an explicit representation of the object in the sensory input system of its animal behavior guidance system. Though telesensory animals are hardwired to adapt their animal behavior to the locations of objects, those objects are not explicitly represented as being located in space.

In subjective animals, objects are represented as being located in space. Spatial imagination gives them a conception of the structure of space, and so they can think about the spatial relations of objects in terms of the effects of motion on them. This is an intuitive understanding of spatial causation. Subjective animals always see the actual spatial relations among objects against the background of the other spatial relations that are possible as a result of motion. Though geometrical structures are included in their telesensory images of objects in space, the objects in space are not explicitly represented as having geometrical structures.

In manipulative animals, objects in space are represented as having geometrical structures. Structural imagination gives them a conception of geometrical structures, and thus, they can think about the geometrical structures of objects in terms of the effects of manipulation on them. This is an intuitive understanding of structural causation. Manipulative animals always see the actual geometrical structures of objects in space against the background of the other geometrical structures that are possible as a result of manipulation. Though states of affairs are included in their representations of the world, those states of affairs are not explicitly represented as states of affairs.

In linguistic animals, the natural world is represented as having states of affairs. Naturalistic imagination gives them a conception of states of objects in space, either as events taking place or conditions that simply hold at some time, and thus, they can think about states of affairs in terms of their effects and their causes. This is an intuitive understanding of efficient causation. Though the regularities behind the most basic causal connections are built into naturalistic imagination by how it is based on spatial and structural imagination, other regularities can be internalized from experience and used in a similar way, for example, how objects are changed by fire, plants grow or can be killed, how animals behave in certain situations, and even how their own children become adults. Linguistic animals can always see the actual states of affairs against the background of the other states of affairs that are possible because of how other states of affairs might affect them or work together with them to produce effects. This is the kind of understanding that is involved in sharing a plan of social level behavior, but it can be used to explain how other states of affairs are caused or to predict the effects they will have.

Truth and logic. Natural sentences can exist as public objects, namely, as overt verbal behavior. (It is just speaking at the primitive spiritual stage of evolution, though after the advent of writing at the next spiritual stage of evolution, sentences can also exist as permanent results of overt verbal behavior.) Such public objects correspond to states of affairs in the natural world. When the states to which they correspond actually exist, the natural sentences are true, and when the states to not exist, the natural sentences are false. But this relationship of correspondence between natural sentences and states of affairs in the world is not direct. It is mediated by the faculty of naturalistic imagination.

This theory about the nature of truth for natural sentences is one of the necessary truths of ontological philosophy. It follows from the inevitability of the evolution of the linguistic level of neurological organization, because the correspondence between sentences and world is mediated by the faculty of naturalistic imagination. The verbal side of linguistic representations is connected to the nonverbal side, as we have seen, by Wernicke’s area. But that means that words acquire their references to objects or kinds of objects by way of their meanings, that is, by way of the images that they name in naturalistic imagination (of all kinds, local, object, telesensory and tactile). Naturalistic images represent states of objects in space as states of objects in space because they are constructed in naturalistic imagination by superimposing one image on another as a representation of something about objects in the local scene. That act of imagination explains how the grammatical structure of a sentence is relevant to its truth.

Logical entailments among sentences are explained by their meanings. One sentence is entailed by another just in case its naturalistic image is already constructed in the process of constructing the naturalistic image of the other. Logical connectives, such as “and,” “or,” and “not” would be introduced to make clear in verbal behavior how naturalistic images are to be combined as parts of a plan or description of the natural world. And the gradual evolution of the capacity to use a language of natural sentences would make it possible to include many predications in a single sentence (by the evolution of more versatile grammatical markers that make it possible for members to learn how to use phrases, clauses, modifiers, and the like).

“If . . .then . . “ might also evolve at this stage. But it would probably not be used to represent logical entailments between sentences, since they would be too obvious. Rather, “if . . . then . . .” would be used to represent the causal relations between states of affairs that could be understood with a faculty of naturalistic imagination. Their understanding of efficient cause relations would include not only all the basic regularities about change of location by motion and constraints on change imposed by the geometrical structures of objects in space, but also all the regularities that they have observed in the natural world, and it would be useful at time to share a mutual recognition of them. Such shared understanding of causal connections is crucial to sharing a plan of social level behavior.

Meaning and reference. This explanation of the evolution of language clarifies something about the ontological assumptions on which this philosophical argument is based. In postulating substances as causes in explaining the world ontologically, we assumed that certain aspects are constituted by the existence of substances, such as their existence and essence. This was to explain properties ontologically, without having to postulate properties as existing in addition to substances. But I did not explain how specific aspects of substances could be picked out or distinguished from one another. I simply used language to refer to those aspects and talked about them as properties of substances. The missing explanation of that ability, or at least, the foundation for it, is provided by this explanation of the evolution of language. It shows how the semantic relation is mediated by images in the faculty of naturalistic imagination.

Each word has a meaning as well as a referent, and its meaning is responsible for its reference to an object or a kind of objects in the world. Its meaning is the image that is connected to it by Wernicke’s area, and it is because that image corresponds by way of the primate faculty of imagination to an object, location, kind of object, or relation in the world that the word refers to objects, properties and relations. Likewise the meaning of a whole sentence is the naturalistic image that is connected to the natural sentence by Wernicke’s area, and it is because the naturalistic image corresponds (by way of the meanings of its constituent words and their grammatical relations in the faculty of imagination to a state of affairs in the natural world) that the natural sentence refers to such a state of affairs in the natural world.

What has been explained by ontological philosophy are the substances and aspects of substances to which words and sentences refer. Particular objects are all constituted by space and matter in some way, and particular substances fall into kinds because they have aspects of the same kinds. Those aspects of particular substances have all been explained as aspects entailed by the existence of two opposite kinds of basic substances, space and matter, and how they exist together as the objects in question. But that ontological explanation depends on being able to see that the basic substances have aspects, including their relations as parts of the same world, and how they constitute objects with the properties in question.

The reason it is possible for us to understand such an ontologically deep explanation of the world is that language acquires its relationship to the world by way of the a faculty of imagination based on the primate animal system of representation, which represents the most basic aspects of the world, its spatial and spatio-temporal structure. Spatial imagination represents the world in a way that makes it possible, in principle, to keep track of objects by their locations in space over time. The location of an object in the local image is a location in the entire world, and thus, with the evolution of language, that makes it possible to refer to any particular object unambiguously by its location in space at some time. Local images also make it possible to refer to spatial relations among objects, and how sequences of images over time represent change over time makes it possible to refer to temporal relations. The object images added by structural imagination represent the geometrical structures of objects in space, and thus, words can refer to some of the most basic properties of substances in a spatiomaterial world, along with whatever properties are represented in telesensory (and tactile, including taste) images of them. Naturalistic images constructed out of such images in naturalistic imagination can correspond to states of affairs, which are aspects of the world (that is, substances having properties). Naturalistic images with a kind of object as grammatical subject correspond to complex properties (that is, properties having properties, or aspects of aspects). But it is the meanings provided by a faculty of imagination whose very structure represents the basic, spatial nature of the world that explains what words and sentences refer to.

The gradual evolution of primitive spiritual animals. Having seen how the evolution of a primitive language of natural sentences in nomadic bands of hominids was both functional and possible, we conclude that its evolution was inevitable. It remains only to be seen what evidence there is for such a stage of evolution on earth. It is not obvious from fossils or artifacts when language first evolved, and so it will help, if we are clear about the traits we are looking for.

What makes primitive spiritual animals different from nomadic bands of hominids is the use of language to coordinate the members’ behavior in controlling conditions that affect the reproduction of the spiritual animal as a whole. Since the main relevant condition that could have be brought under control by a primitive language was acquiring free energy, coordinating behavior in hunting large animals was probably its original function. But the capacity to coordinate their behavior would have caused many other changes.

The leader’s plan for hunting behavior is only the simplest and most obvious use of language to coordinate behavior, but the capacity to share a common intention would also have changed the relations of members within spiritual animals. Nomadic bands of primates would acquire customs, but in spiritual animals, such habits and expectations would come to be mediated by the exchange of linguistic representations. Ways of behaving in certain situations would be named, and the capacity to refer to such roles would tie different practices together. Given the crucial role of the leader in guiding social level behavior, for example, there would be a special name for the member playing that role, and they might insist on customary behavior in other situations by referring to them as his instructions. Special words would evolve to describe kinship relations (though it the leader were the father of most of the children in the group, only the mother child relationship would need to be mentioned).

This is probably also the stage at which food-sharing evolved. The use of language to coordinate behavior made it possible to arrange for one group to wander around gathering vegetables while another group hunted animals, and then all meet again later at a specific location to share food. In the evolution of human beings, this division of labor was made along lines of gender. Thus, language use may have been responsible for the evolution of the unusually extreme sexual dimorphism between females and males, including perhaps the year-round sexual activity, frontal sexual intercourse, and the emotionally revealing facial expressions that transformed mating into a tighter social bond.

What is required to have the power of spiritual animals was not that a plan be distributed by the leader, but that everyone somehow share the same plan for social level behavior. That is the essence of the spiritual animal, for it includes both the social and the cultural aspect. And though it could also be accomplished without formal instructions from a leader, it is language that ties those two aspects together.

The combination of a verbal and nonverbal side in linguistic representations it what ties them together, for the verbal side is responsible for the social aspect and the nonverbal side is responsible for the cultural aspect. Since the nonverbal side consists of naturalistic images in the faculty of imagination, it is private. But the verbal side can be generated overtly, and its status as a public, observable object makes it possible for linguistic representations to serve as a structural cause for coordinating the members’ behavior. Without public linguistic interactions, it would not be possible to distribute a plan of social level behavior. The social aspect of the spiritual animal is the continual linguistic interactions among its members.

What enables linguistic interactions to provide a structural cause for social level behavior is that they are representations which can correspond to the world. The verbal side of linguistic representations is just a re-representation of representations in naturalistic imagination, for their function is to control the construction of naturalistic images in the listeners’ faculties of imagination. This public control of the images formed in imagination can induce in each brain a representation of the same state of affairs in the world. Each brain has object images for the same members and other objects in the local scene, and each brain combines them in the same way so that each corresponds to the same social level behavior of the whole. And this shared plan can coordinate their behavior, as we have seen, because each member recognizes a different one of the object images representing members as his own body and understands that the behavior predicated of it is how he must behave. This unique part-whole relationship is crucial, for it is essential to its function as a structural cause that each member of the spiritual animal see itself as a different part of the whole plan. But otherwise, the exchange of linguistic representations causes each brain to contain the same kind of nonverbal representation of their social level behavior as taking place in the same natural world. That is the cultural aspect of the spiritual animal. And since all such linguistic representations are (potentially) complete in each brain, the cultural aspect is as much a structure of the spiritual animal as a whole as the social aspect.

Evidence of such primitive spiritual animals (stage 8) depends on being able to distinguish them from nomadic bands of hominids, which are part of the radiation of primates (stage 7). There is good evidence that primates radiated into the grasslands around their arboreal homes in Africa 5 or even 10 million years ago, when large regions of forests were replaced by grasslands as the climate changed.

Bipedalism, the defining trait of hominids, is evident in the earliest fossil, know as “Lucy”, which dates back about 3.5 million years. With a brain the size of a gorilla, but a smaller body, she represents a species called Australopithecus afarensis. Apparently, there were also several other forms of Australopithecus at the time, such as africanus, robustus, and boisei, all of which were extinct by about 1.3 million years ago. (See Fisher, 1988.)

The greater facility at tool use that we expect to evolve in primates carrying clubs is evident in Homo habilis, which showed up about two million years ago. Habilis was still quite small, about three feet, the size of Australopithecus afarensis (judging by a fossil from 1.8 million years ago that was discovered in 1986). But Habilis is distinguished by evidence of greater use of stone tools. Whereas Australopithecus cracked pebbles, presumably to use as cutters and scrapers, Homo habilis made bi-facial stone tools (Acheulian culture), which could have been used for hunting animals. Some refinement of the primate structural imagination may have enabled them to use stones more effectively. Or perhaps it was the evolution of an opposable thumb.

There are two candidates for primitive spiritual animals in the archeological record, Homo erectus and archaic humans (such as Neanderthal Man, or Homo sapiens). Homo erectus evolved some 1.6 million years ago, about the time that Homo habilis became extinct (dated by fossils at 1.8 million years ago). But Homo erectus had become extinct by 250,000 years ago, about the time archaic humans evolved. It was Neanderthal Man, a species of archaic humans, that Cro Magnon Man replaced in Europe 35,000 years ago, not Homo erectus. It is agreed on all sides that Cro Magnon Man is our own species, and since that is, as we shall see, a later stage in the evolution of spiritual animals, the question is, Which species, Homo erectus or archaic humans, were the first spiritual animals (stage 8)?

Homo erectus had larger bodies than Homo habilis, within the modern body-height range, and their skulls indicate a relatively greater increase in brain size (1000cc on average, compared to about 500cc for Habilis).

There are two reasons for thinking that their larger brains gave Homo erectus the use of a primitive language.

First, Homo habilis became extinct about the time Homo erectus evolved, and the inherently greater power of spiritual animals would explain why nomadic bands of hominids became extinct.

Second, Homo erectus were the first species of this lineage to leave Africa and invade territories ranging from Europe to the Far East. This could be explained by the evolution of the use of natural sentences, because the increased capacity to coordinate behavior in hunting would have enabled them to acquire energy from larger animals, and that could have been what opened up those new habitats to them.

On the other hand, these facts can also be explained on the assumption that Homo erectus was just a late phase in the evolution of animal societies of hominids. We have seen that societies of non-primate animals can evolve instincts for more complex forms of social coordination using animal cries as signals, such as the wild dogs of Africa that are supposed to prey on ungulates by herding them into ambushes. Such an increase in their power to acquire free energy would explain both the extinction of Homo habilis in Africa and the ability of Homo erectus to migrate out of Africa. More sophisticated signs also explains two other facts that would be surprising, if Homo erectus could speak.

First, it would explain why there is no great change in their technology. The use of natural sentences should greatly improve their technology, because it would enable individuals to share their understanding of causal connections and accumulate culture based on tools. However, Homo erectus still used bi-facial stone tools, like Homo habilis. Even if they needed to control fire with them in order to invade colder climates, that is something that could be accomplished by simply carrying small fires with them.

Their lack of language would also explain why there is no evidence in Homo erectus of the changes in the larynx that seem to be required to generate the highly modulated types of sounds required for speech.

In archaic humans, such as Neanderthal Man, by contrast, the fossils and tools that remain indicate both kinds of changes, technological and physiological, as well as the fate of Homo erectus.

First, flint tools and hafted stones indicate that archaic humans had a more advanced (Mousterian) culture, as we would expect of animals with a greater understanding of causal connections.

There is also fossil evidence of changes in the larynx that suggest a much increased reliance on highly modulated sounds.

Moreover, if archaic humans did have a primitive language of natural sentences, their capacity to coordinate behavior could explain why Homo erectus became extinct about the time that Neanderthal Man and other species of archaic humans showed up. That is, Homo erectus were the societies of hominids on which archaic humans preyed, before they took up war against one another.

It seems likely, therefore, that Neanderthal Man (that is, archaic humans, or Homo sapiens) represents the primitive spiritual stage of evolution in the history of evolution on Earth.

9 Reflective stage (Rational spiritual animals). The primitive spiritual animal, as we have seen, is the new kind of animal that is possible only at the social level of biological organization. The behavior guidance system for its social level behavior is language. But it is just a primitive language of natural sentences, and there is another inevitable stage in the evolution of spiritual animals. There is a higher level of neurological organization that is both functional and possible, whose nature is evident in the grammatical structure of psychological sentences, the new kind of linguistic representations used at the reflective stage. Its function is easily understood by us, for we can reflect on how we use psychological sentences. But there is room to doubt the inevitability of the reflective stage. It may not seem possible in the relevant sense, for it is not obvious why the use of psychological sentences would evolve in the first place.

The nature of the higher level of neurological organization is evident in the difference between the grammar of natural sentences and the grammar of the new psychological sentences. Natural sentences have a simple grammar of subject and predicate (though many predications can occur in a single natural sentence). The grammatical subject of psychological sentences is restricted to subjective animals, a certain kind of object in space, and its predicate includes a verb of propositional attitude together with the name of the proposition (such as a naturalistic image) to which the attitude is taken. Such verbs of propositional attitude include “perceive,” “believe,” “imagine,” desire,” and “intend,” and what follows the verb is a word or sentence indicating the proposition toward which is the attitude is taken (that is, what is perceived, believed, etc.).

What shows that psychological sentences are on a higher level of neurological organization is not simply that natural sentences can be parts of them. Natural sentences may already be parts of natural sentences, for example, as phrases, clauses, and even modifiers as well as compound natural sentence (formed by conjunction). Psychological sentences indicate a higher level of organization because the natural sentences included in them are parts of a new kind of grammatical structure, which represents the proposition (that is, the meaning of the embedded sentence) as playing a certain role in causing the subject’s behavior or beliefs.

Psychological states are what is represented by the predicates of psychological sentences, and so psychological sentences represent objects as having psychological states, that is, as subjects. This is something beyond what natural sentences can do, for they represent only naturalistic states, or states of objects in space (such as objects having relations in space, objects having geometrical or other properties, and the like). (Thus, although natural sentences can describe spoken words and sentences as public objects, that is, as verbal behavior, they cannot represent them as words and sentences.)

The function of psychological sentences is to represent the causal roles that linguistic representations play in the processes of guiding the behavior of an animal subject, as a way of explaining the subject’s behavior (or beliefs). Beings like us can understand how the use of psychological sentences facilitates such explanations, because we can reflect on how we use them, for example, to “see into the minds” of other subjects.

By reflecting on how we know about other subjects, we know that we can often explain the causes of their behavior by putting ourselves in the other’s position and imagining what we would do. We take the beliefs and desires that would lead us to behave the same way as explaining the other’s behavior. Thus, when we know something about how others behave, we can generally figure out what desire is moving them and what their intentions are, for we can assume that they have beliefs about the world are generally held and believe whatever perception tells them about their particular situation. We see into their minds by inferring to the sets of beliefs and desires that best explains their behavior.

Psychological sentence also makes the users reflective, for they can be used to explain their own behavior (or beliefs). Though psychological states are just causes of the behavior (and beliefs) at work in the animal behavior guidance system, the capacity of the subject to reflect on those causes evolves into an important part of the very process by which they case behavior (or beliefs), and that earns them the special name, “reasons.” Reasons are causes that are represented as causes as part of their process of causing.

More generally, to be able to use psychological sentences is to have a faculty of “rational imagination.” It is a form of imagination, like those that have preceded it, except that it gives the user the ability to understand “rational causation.” They can see reasons as causes in other subjects, in themselves, or in general, that is, as arguments about what to do or what to believe. Thus, reflection makes the linguistic subject rational.

The most spectacular accomplishments of the reflective stage come from how the exchange arguments constitutes another form of reproductive causation, which is responsible for cultural evolution. Cultural evolution is another example of the reproductive global regularity we have called “gradual evolution.”

Though cultural evolution is contained within the spiritual animal, it works in basically the same way as biological evolution, that is, by how reproductive cycles of arguments add up in the space provided by a spiritual animal as time passes.

Since the use of psychological sentences includes the capacity to construct linguistic representations in which a conclusion comes together with reasons for it attached, it is possible to engage in a new kind of linguistic interaction: arguing. The exchange of arguments, as we shall see, gives rise to a new form of evolution by reproductive causation: cultural evolution. With the same kind of ontological cause as gradual biological evolution, the same kind of ontological effect follows, namely, the gradual evolution of culture toward natural perfection for reproducing organisms of its kind, that is, the natural perfection of arguments, which is to know the good, the true and the beautiful.

Cultural evolution is such an important part of the gradual change that takes place at the reflective stage that this section is divided into to main subsections: biological evolution and cultural evolution.

Biological evolution will show that the evolution of the reflective level of neurological organization is inevitable, by showing not only that it opens up a new range of powers to control relevant conditions, but also that it will eventually be tried out as a random variation in circumstances in which it is functional, so that is naturally selected.

Cultural evolution will show that cultural evolution is a form of reproductive causation that is contained in rational spiritual animals (by showing how arguments are “organisms” that impose natural selection on themselves by going through reproductive cycles). It will also show that, even under the most favorable conditions, gradual evolution of culture at the rational spiritual stage leads to a natural perfection for arguments of its kind that includes certain dichotomies that limit the power of reason to control relevant conditions.

Biological evolution of the reflective level. Primitive spiritual animals are a form of life, by our definition, because they are products of reproductive causation with the autonomous activity of going through reproductive cycles on their own. And as a form of life, they make themselves evolve by imposing natural selection on themselves. But the linguistic stage is merely the first stage in the gradual evolution of spiritual animals. It merely prepares the way for the reflective stage.

The reflective stage of evolution is the ninth stage, by our reckoning, in the series of stages leading up to beings like us. The organism that evolves at the ninth stage is the rational spiritual animal. The use of a primitive language, the behavior guidance system that accounts for the origin of spiritual animals at the previous stage, is transformed into a more powerful behavior guidance system, called “reason.” Indeed, reason is so good at controlling relevant conditions that it takes over the function of guiding all behavior, at the individual as well as the social level.

What makes reason the source of such great power powerful is that rational spiritual animals constitute a new form of reproductive causation, in which the arguments accumulated as culture evolve gradually in the direction of natural perfection for “organisms” of their kind. Since that includes knowing what is good, cultural evolution makes reason increasingly powerful.

It is cultural evolution during the reflective stage that leads to another stage of evolution, (stage 10, the philosophical stage), not biological evolution. The philosophical level of neurological organization does not require any genetic changes (that is, changes supplied by the mechanism of embryological development, the multicellular biological behavior guidance system).

Revolutionary changes in evolution are, however, a reproductive global regularity. Like all previous evolutionary stages, the reflective stage is caused by a higher level of part-whole complexity about the reproducing organisms. It is a higher level of neurological organization in the series we are following.

The direction of evolution at every stage is natural perfection, or maximum holistic power, and the gradual evolution of primitive spiritual animals prepares the way for rational spiritual animals. When gradual evolution makes the nervous structures involved in using natural sentences reliable enough, it is possible for them to serve as parts of a larger structure in the nervous system, for using psychological sentences.

But the next stage is inevitable, according to reproductive causation, only if it is both functional and possible. Its functionality depends on the higher level of organization opening up a whole new range of powers that can evolve gradually over a long period as a result of the natural selection that they impose on themselves. And its possibility depends on whether the higher level of neurological organization can be tried out as a radical random variation on the structures of the organisms that are evolving at the previous stage.

The function of the reflective level of neurological organization is not very problematic, because it is exhibited so clearly in the grammatical structure of psychological sentences and the way in which they are used. But its possibility is less obvious.

Given the capacity of the mechanism of embryological development to try out random variations, the higher level of neurological organization itself is hardly an obstacle to the evolution of reason. But if the power of the reflective level comes mainly from the cultural evolution of arguments it constitutes, it may be hard to see how reason could evolve by the natural selection of a radical random variation on linguistic brains.

There is, however, something that that makes the evolution the reflective level is inevitable. As we shall see after considering more carefully the nature and function of the reflective level of neurological organization, an urgent need arises late in the linguistic stage of evolution that makes even a very simple and weak form of reflection crucial to controlling conditions that affect reproduction.

Function of the reflective level of neurological organization. The nature of the reflective level of neurological organization that causes the reflective stage of evolution is indicated by the grammar of the new kind of sentences that are used at this stage. But behind that linguistic structure, making the use of psychological sentences possible, is a new form of imagination: rational imagination. And like each of the previous evolutionary stages, the new kind of understanding that rational imagination affords is the source of the new powers that are acquired in the long period of gradual evolution at the reflective stage.

Psychological sentences. Psychological sentences, like natural sentences, have a simple subject-predicate grammar. But their grammatical subject refers only to subjective animals (or objects assumed to be like them), and the predicate is not of the kind found in natural sentences. Its meaning cannot be explained by simple predication.

The psychological predicate is made up of a verb of propositional attitude and the name of a proposition (a natural or psychological sentence) to which the attitude is taken.

Verbs of propositional attitude represent the causal roles that propositions play in guiding animal behavior. The propositional attitudes include perceiving, believing, remembering, imagining, desiring, and intending. But the kinds of verbs of propositional attitude fall into two basic groups, beliefs and desires, depending on whether the attitudes have to do with input to the behavior guidance system or selecting and generating its output.

Psychological predicates represent what are called “psychological states.” Thus, psychological sentences predicate psychological states of certain kinds of objects in space. The kinds of objects that have psychological states are animals with at least a subjective animal behavior guidance system (or objects thought to be like them), and thus, psychological sentences represent objects in space as subjects.

The psychological states picked out by psychological sentence are states that play causal roles in determining behavior and beliefs. They are causally relevant states of the subjective animal behavior guidance system.

Beliefs and desires combine, as we have seen, to give animal subjects intentions, which generate their bodily behavior. Desires determine the goals, and beliefs determine the means.

But beliefs also have causes in the animal behavior guidance system, for they can be caused by perceptions. The causal roles that perceptions play in determining beliefs can be as complex as those involved in determining behavior. Besides giving the subject beliefs about currently perceived objects, current perceptions can combine with already formed beliefs to change beliefs about currently unperceived objects. And perceptual reports made by others can have a similar effect.

The meanings of psychological sentences derive, therefore, from their use in explaining and predicting behavior (or beliefs). But in order to be used in that way, the speaker and listener must both have a faculty of imagination by which to understand explanations of behavior and beliefs.

Just as understanding the structure of space depends on spatial imagination, understanding structural causes depends on structural imagination, and understanding natural sentences depends on naturalistic imagination, understanding psychological sentence depends on a form of imagination. It will be called “rational imagination” (though it might just as well be called “psychological imagination,” “subjectivistic imagination” or even “reflective imagination”).

As the function of psychological sentences suggests, that new faculty of imagination is basically the subject’s own animal behavior guidance system. That is, the ability to think about psychological states as causes of behavior (or beliefs) in another subject, for example, comes from using one’s own brain to simulate the behavior guiding process in the other’s brain. To use a psychological sentence to represent the psychological state of another subject is to temporarily impose that psychological state on one’s own brain as an act of imagination while thinking of it as belonging to the other. The further changes it causes in one’s own brain state are then seen as happening in the other subject.

The grammar of psychological sentences is, therefore, and indication of a higher level of neurological organization in the faculty of imagination. The meaning of a natural sentence embedded in a psychological predicate is not merely conjoined with other predications as part of a complex naturalistic image. (Nor is it a disguised form of predication, like a clause or phrase.) Instead, the verb of propositional attitude represents the naturalistic image (or proposition) as playing some role in a behavior guiding process. The ability to use psychological sentences requires, therefore, a brain mechanism that handles natural propositions in a new way, one that is based on its already being a representation and that represents it as having a further role in guiding behavior.

Since the psychological sentence represents a new way of handling the meanings of whole sentences in the faculty of imagination, it can handle the meanings of psychological sentences in the same way. Thus, subjects can have beliefs and desires about the psychological states of subjects, such as desiring that someone love them and believing that they do not.

Rational imagination. The capacity to represent the world in some way depends on having a system that can represent what is actual against the background of what is possible. What is possible are changes of some kind that can occur as an effect or as a cause of what is supposed to be actual. The capacity to see the possible is provided, as we have seen, by the faculty of imagination, which evolves by stages in the animal behavior guidance system.

Form of imagination. In telesensory animals, the object is represented as a object of a certain kind only because it can also recognize objects of other kinds. But since the other possible kind of objects are not represented by images that can be called up from memory by covert behavior, telesensory animals lack imagination altogether. And the advent of imagination makes it possible to represent objects as having other aspects than just their kinds.

The subjective animal’s spatial imagination makes it possible to represent objects as being located in space, because it gives the animal a conception of space. With spatial imagination to can call up sequences of images that represent the effects of motion, it can see actual objects against the background of how they might be different because of their motion relative to one another.

The manipulative animal’s structural imagination makes it possible to represent objects in space as having geometrical structures, because it gives the animal a conception of geometrical structure. With structural imagination to call up sequences of images representing the consequences of manipulation, it can see the actual geometrical structures of objects against the background of how they might be different by manipulation.

The linguistic animal’s naturalistic imagination makes it possible to represent objects in space as having certain states, because it gives the animal the conception of a state of affairs. With naturalistic imagination to call up sequences of images representing the regularities among states involved in causal connections, it can see naturalistic states against the background of how things might be different as a result of efficient causation.

The reflective animal’s rational imagination likewise makes it possible to represent certain kinds of objects in space, namely, subjects, as having psychological states, because it gives the reflective subject the conception of a psychological state. The capacity to represent psychological states is the capacity to see having those states against the background of what other psychological states are possible, including not only how they are different from other possible psychological state, but also now they might cause or be caused by other psychological states.

The structure of the faculty of imagination. Imagination first evolved with the subjective animal as a higher level of neurological organization than telesensory animals, and we have seen how the two succeeding animal stages of evolution were caused (at least in part) by a higher level neurological organization within the faculty of spatial imagination. A brief review will show how rational imagination is just another level of part-whole complexity in that series.

The subjective animal uses input about its current bodily condition to assemble telesensory images as a local image representing objects in the local scene from the point of view of it body, and spatial imagination is the capacity to think about spatial relations among objects by using covert locomotion to call up from memory sequences of local images that represent the effects of motion relative to objects in its territory. We have seen how systems recognizable in the anatomical structure of the mammalian brain serves all the subfunctions required for spatial imagination, and that is the framework in which all the subsequent forms of imagination evolve.

Structural imagination is the capacity to think about the geometrical structures of objects in space by using covert manipulation to call up from memory sequences of telesensory images within a (perceived or imagined) local image that represent the results of objects rotating and interacting with one another. Its higher level of neurological organization was possible because it used the same mechanism for recording images together in sequences in memory as spatial imagination, except that instead of storing multiple sequences of local images as a map of the effects of locomotion in various direction in the entire territory, multiple sequences of telesensory images of objects were stored as an object image that had to be located within a local image.

Naturalistic imagination is basically the capacity to combine images of various kinds (telesensory images as well as local and object images from spatial and structural imagination) as parts of naturalistic images, which represent states of affairs in the natural world (for example, an animal being of a certain kind or behaving in a certain way).

Images that derive from lower levels of neurological organization are the meanings of the (nonlogical and nongrammatical) words used in natural sentences. The local image gives the object a location in the world (real or imaginary) and represents spatial relations among them, whereas object images (as well as telesensory and tactile images) represent kinds of objects according to their perceptible properties, geometrical structures or dispositions. (Such meanings can be more or less complex depending on how many different sequences of images are united in them)

The effect of combining such images in naturalistic imagination is to generate a new sequence of images, or a naturalistic image, which depends on them. The combination is asymmetrical, because there is a difference between using an image as the grammatical subject of natural sentences and using it as a predicate. The naturalistic image is the meaning of the natural sentence, which represents an object as being an object of a certain kind, as being located in a certain place, or as having some other naturalistic state. Thus, by using covert linguistic manipulation to construct naturalistic images, the subject can think about states of affairs in the world, and the effects of imposing it temporarily on the memory of one’s own sensory input system (the beliefs that accumulate with one’s map of the territory) are its implications, including its role as a efficient cause or effect.

But natural sentences are representations in the linguistic system of representation, and in order to serve their social function of coordinating behavior, it must be possible to represent the covert nonverbal behavior of naturalistic imagination publicly, as overt verbal behavior, including both words indicating the images (or meanings) that pick out objects, properties or relations in the world and grammatical markers for those words indicating how those meanings had been combined in naturalistic imagination (that is, as grammatical subject, predicate, etc.). The words and grammatical markers combined in the sentence must enable another language user to construct the same naturalistic image in her own naturalistic imagination.

Rational imagination is basically the capacity to use psychological images to represent the psychological states of subjective animals. Psychological images are the meanings of psychological sentences, and just as the structure of naturalistic images is evident in natural sentences, so the structure of psychological images is evident in psychological sentences. Rational imagination requires a higher level of neurological organization than naturalistic imagination in much the same way that naturalistic imagination was higher than both spatial imagination and structural imagination (and in contrast to how structural imagination is higher than spatial imagination, as indicated in the functional diagram of the reflective animal behavior guidance system).

Psychological images are made by combining naturalistic images (or psychological images) as parts of a larger (psychological) image, which represents the causal roles that those images play in causing behavior (and beliefs) in subjective animals. Psychological images are constructed in the sensory input system by linguistic behavioral schemata in the behavioral output system, and in both systems, it requires a higher level of neurological organization. By using covert nonverbal behavior to construct the meanings of psychological sentences, one temporarily imposes the psychological states one would attribute to another subject on one’s own brain, and the effects of those temporary beliefs or desires on one’s own beliefs and desires are the conclusions that follow from them. But since this is all predicated of some subject, the psychological state and its implications are seen as occurring in some subject.

There are two basically different kinds of psychological images, beliefs and desires (or intentions), because naturalistic (and psychological) images play two basically different roles in the sensory input system and the behavioral output system. The sensory input system contains the memory map of the animals territory and all the general and particular beliefs about the world that accumulate about its objects, including, at the rational stage, beliefs about some of those objects as subjects (with psychological states). Desires are basically dispositions to behave in certain ways towards objects of certain kinds, and they are represented like intentions, by behavioral schemata (and as images in the sensory input system of other bodies behaving appropriately). Reflective linguistic acts must, therefore, be able to impose the meanings of sentences on the brain in two basically different ways.

That is the nonverbal side of the reflective linguistic act, but since psychological sentences are representations in the linguistic system of representation, they must also serve its social function of coordinating behavior. Thus, the covert nonverbal behavior in rational imagination must be represented publicly in the speaker’s overt verbal behavior so that listeners can reconstruct the psychological image in their own imaginations, calling up sequences of images of the same kinds. (See below, Structure of reflective brain.)

Understanding of rational causation. The faculty of rational imagination is a way of understanding how psychological states are causes of behavior and beliefs. The sequences of images that are called up in rational imagination as a result of constructing a psychological image represent regularities that hold of subjective animals generally, because animal behavior guidance systems all work in basically the same way, with beliefs and desires determining intentions (and perception together with background beliefs determining new beliefs). With inferences built into the structure of rational imagination, the changes that occur in one’s own beliefs or intentions as a result of constructing a psychological image in rational imagination correspond to what would happen in other brains (though the fit is more detailed the more the other subject resembles a reflective subject, with rational imagination). But since it is a psychological image, it is the representation of some object as a subject, that is, as having the psychological state (as indicated by the grammatical structure of the psychological sentence).

Rational imagination is, therefore, a way of understanding a kind of causal connections in the world. In this case, the causes have to do only with the behavior (or beliefs) of subjects, rather than the behavior of objects in space generally. Thus, just as spatial imagination affords an intuitive understanding of spatial causation, and structural imagination affords an intuitive understanding of structural causation, and naturalistic imagination affords an intuitive understanding of efficient causation, so rational imagination affords an intuitive understanding of rational causation.

Rational imagination can be used to predict the behavior of subjects in any situation. Several psychological states may have to be predicated of the subject to represent all the relevant beliefs about the situation he is in and the various desires (or longer range intentions) that are at work in him. They are all held together as parts of the psychological image. And they are all imposed at once as a temporary modification on one’s own worldview and goals, as if one were in the other’s situation. But they are parts of a psychological image, and so they are seen as states of the other subject. The changes that occur in one’s beliefs or intentions are the predictions one makes about the other subject, given those premises. The conclusions may be just inferences about what the subject would come to believe. But when it leads to new intentions, it is a prediction of the subject’s behavior.

But the understanding of rational causation can be used in other ways. When the other subject’s overt behavior is what is known, rational imagination can be used to infer the intention or motivating desire. Along with common background beliefs, the other subject is assumed to have whatever additional, relevant beliefs that come from where he is located. In order to discover his intentions, it is only necessary to compare possible sets of desires and beliefs and the intentions to which they would lead, for it is basically an inference to the best rational explanation of the behavior that is observed. Thus, one can “see into the other subject’s mind.”

Since psychological sentences can be used to understand one’s own beliefs and desires, as well as others, evolution at this stage leads to the ability to represent the causes of one’s own behavior, as causes of behavior, as part of the very process of causing the behavior. This means that subjective animals with the use of psychological sentences are reflective subjects.

It is not merely that reflective subjects monitor the desires and beliefs that are causing their behavior. More than that, as we shall see, the desire to submit to a leader’s instructions evolves into the desire to submit to reason, and thus, reflective subjects can do what they discover in rational imagination to be the best course of action, all things considered, even when it is opposed by strong, immediate desires to the contrary. That is the “autonomy of reason.”

This transformation of the causes of behavior in reflective subjects has given those causes a special name in ordinary language: “reasons.” Thus, reasons are causes. But they are causes of a special kind, because they depend on being represented as causes in order to be effective as causes of behavior (or beliefs) at all. That makes reflective subjects enormously powerful, for as we shall see, not only does it enable them to control the conditions that affect their reproduction, but to control other conditions that they see as good. It is an indication of the autonomy of reason.

From telesensory animals on, the animal behavior guidance system has had a conception of the object, and we have seen how it is enriched by stages with the conception of their locations in space, their geometrical structures, and their naturalistic states. That might be described as the evolution of the the “concept of the object.” But with the advent of rational imagination, the subject has the conception of the subject, that is, of objects as having psychological states. Since that is based on an way of understanding psychological states as causes or effects, that is, as reasons for the conclusions drawn by their animal behavior guidance systems, it means that a whole new world of facts opens up to reflective subjects. Reflective subjects can see into one another’s minds, and that begins an evolutionary stage in which they become increasingly powerful in controlling all the conditions that affect their reproduction, not only conditions in the natural world, but also conditions in a world of subjects who can all see into one another’s minds.

The possibility of the reflective level of neurological organization. Having seen how a higher level of neurological organization could open up an entire range of new powers to control relevant conditions, we can conclude that its evolution is inevitable, if it is possible, in the sense that it can be tried out as a random variation and naturally selected for such a function. There is not much reason to doubt its possibility when it comes to the capacity of the mechanism of embryological development to try setting up brains with reflective imagination, because the reflective level occurs in the faculty of imagination. But at first, the reflective level of neurological organization would be much simpler and weaker than the capacity for reason we have been considering, since the brain mechanisms on which beings like us can reflect on are informed by many centuries of cultural evolution. Thus, it may not be obvious how, even if a higher level of neurological organization were tried out as a random variation, it would be naturally selected. But before we take up that problem, let us make sure that the reflective level of neurological organization is as simple as it seems to be.

Structure of the reflective brain. The functional diagram of the reflecting animal behavior guidance system shows how nervous systems of the kind we have been considering could incorporate a mechanism for rational imagination. Since the higher level of neurological organization occurs within the faculty of naturalistic imagination, it occurs in each of the systems involved in generating verbal behavior in mere linguistic animals. The psychological linguistic act and psychological image are represented as more encompassing forms of behavior than naturalistic acts and images, because the latter are contained as special parts of the former.

Speaking. In the speaker, the psychological linguistic schema must not only construct all the images of psychological states (beliefs and desires, including both the proposition and the propositional attitude toward it in each case), but also predicate the psychological states of an animal subject. In order to express this nonverbal activity in the rational imagination verbally, a more complex grammatical structure is required. The sentence must identify the naturalistic image (or psychological image) whose causal role is being described, it must identify the kind of causal role predicated of it, and it must identify the subject in whom such a psychological state occurs. Since there is already one predication in any naturalistic image toward which the propositional attitude is taken, a basically new kind of grammatical marker is required to indicate the kind of predication that occurs in constructing psychological images. Those grammatical markers are the verbs of propositional attitude.

Verbs of propositional attitude indicate a kind of predication in which a naturalistic (or psychological) image is represented as playing certain kinds of causal roles in causing behavior (or beliefs). That is, psychological linguistic schemata must be able to construct naturalistic (or other psychological) images in the sensory input system and then temporarily impose them on the speakers brain so that their effects on the brain can represent their implications about intentions (or beliefs). The verbs of propositional attitude represent how they are imposed on the brain, and given the nature of animal behavior guidance systems, there are three basically different causal roles they might have.

Verbs of propositional attitude such as “believe,” “perceive,” and “remember” indicate various ways of imposing naturalistic (or psychological) images on the sensory input system. They constrain the speaker’s behavior guiding processes so that the sequences of images that are called up from memory in rational imagination represent what a subject would infer in certain situations.

Verbs of propositional attitude such as “desires,” “needs,” and “wants” indicate the imposition of naturalistic (psychological) images on the goal direction system of the speaker’s brain. They constrain the speaker’s brain so that the sequences of images that are called up from memory represent what a subject would try to do when certain kinds of behavioral schemata were activated (relative to certain objects).

Verbs of propositional attitude representing intentions indicate the imposition of naturalistic (or psychological) images on the speaker’s behavioral output system. They constrain the speaker’s brain so that the sequences of images that are called up in rational imagination represent the beliefs or desires that might lead a subject to behave with such an intention.

Though there are three basically different kinds of causal roles that such first level propositions might play in behavior guidance processes, the reflective linguistic schemata need only two basically different ways of imposing propositions on the brain, because desires and intentions are both represented in the behavioral output system.

The goal selection system does not represent goals on its own, but only by activating certain kinds of behavioral schemata in the behavioral output system (perhaps, relative to certain objects in the sensory input system). Thus, desires can be represented in rational imagination by imposing propositions on the behavioral output system, for if the kinds of behavior represented are general enough in the situation, the sequences of images called up from memory will be inferences about how to behave in that way (perhaps relative to so object picked out in the sensory input system)

Since there are only two basically different verbs of propositional attitude, no great changes are required of biological evolution in order for linguistic brains to acquire the ability to use psychological sentences. It would be enough for some random variation to try out a mechanism for imposing propositions (naturalistic or psychological images) on the speakers brain in two different ways, one affecting mainly the sensory input system and the other affecting mainly the behavioral output system. The distinctions among kinds of psychological states is each class could then be acquired by learning.

For example, the difference between imposing a naturalistic image as a perception or imposing it as a belief could be acquired as part of the process of learning to impose propositions on the sensory input system, for the difference would show up mainly in the strength of the belief and how easily it could be discounted.

Likewise, the difference between imposing a proposition as a desire and imposing it as an intention could be acquired as a refinement of the capacity to impose propositions on the behavioral output system, for it would merely indicate which of the sequences of images that were called up from memory in rational imagination is relevant, those representing inferences about how to behave (that is, its consequences) and those representing inferences about the beliefs and desires that motivate it (or its causes).

In order for verbal behavior to indicate the activity in the speaker’s rational imagination, the nonverbal covert side of the linguistic act must be expressed verbally, and the job of representing the activity in rational imagination in verbal behavior is performed by Wernicke’s and Broca’s areas as indicated in the functional diagram of the reflective brain. (The projection from the former to the latter is not represented in this functional diagram, but it can be seen in (See the diagram of the linguistic brain in the Linguistic stage, Stage 8.)

The motor output for speaking comes from Broca’s area. But Broca’s area depends on input from Wernicke’s area, because Wernicke’s area is what receives information from rational imagination about how the psychological image is being constructed.

Wernicke’s area must not only give the names of the images (meanings of words) involved, but also have grammatical markers that distinguish one kind of predication from another (that is, the naturalistic predication that may occur in the embedded naturalistic sentence from the predication of the psychological state to some subject). That is the role of verbs of propositional attitude: they are the grammatical markers for the new kind of predication, the one that is involved in imagining subjects as having psychological states.

Since grammatical markers for the predication involved in the construction of naturalistic images has already evolved, they can be embedded in the psychological sentence after the verb of propositional attitude. That is, the naturalistic sentence is contained in the psychological sentence after the verb of propositional attitude, like a name for the naturalistic image toward which the attitude is taken.

With the capacity to distinguish psychological from naturalistic predication, it is possible to treat psychological images in the same way as naturalistic images in rational imagination. Thus, subjects can be seen as having beliefs or desires about beliefs or desires.

Assuming that Wernicke’s area supplies the required words and grammatical markers, Broca’s area can generate the motor commands for the words and the grammatical markers through the motor neocortex. Once again, verbal behavior would be generated by the linguistic schema only indirectly, as a result of thinking the content of the sentence and the effect of the images constructed in imagination on Broca’s area. (See Linguistic stage: Possibility: Structure for details.

Though only the verbal side of linguistic behavior is overt, it can also be generated covertly. That is, one can speak to oneself silently by generating the motor commands for speaking covertly. But it is also possible to carry out the nonverbal side of a linguistic act without generating even covert verbal behavior. That is how the reflective subject normally thinks.

Listening. The listener’s understanding of psychological sentences parallels that of natural sentences. Wernicke’s area constructs the psychological image in the listener’s rational imagination using telesensory input about the speaker’s overt verbal behavior.

Wernicke’s area acquires the nervous mechanisms for decoding verbal behavior in the development of the capacity to speak psychological sentences. The connections between words and the images that are their meanings and between grammatical markers and the ways of combining images that are their meanings are two-way connections (as indicated in the functional diagram). That is, Wernicke’s area uses the words identified in telesensory input to call up the images and the grammatical markers identified in telesensory input to combine them on the inferior parietal role in the same way that the posterior cingulate neocortex would have, if the brain had been speaking the sentence meaningfully. Thus, the listener can grasp the meaning of the sentence heard. Broca’s area is not required for comprehension.

Unlike the previous levels of neurological organization, I cannot point to any additional brain structures that realize the higher level of neurological organization. Its existence is basically an inference from the structure of psychological sentences and their function as a faculty of rational imagination. But given the basic structure of the faculty of imagination, it is plausible, at least, to suppose that there is some new brain structures that enables the reflective brain to impose propositions on the brain in the two basically different ways described above.

Wernicke’s and Broca’s areas of the neocortex are properly evidence of reflective level neurological mechanisms. I cited them as evidence for the evolution of the mechanisms required for the use of natural sentence, but that is just an inference. There are no brains left from the primitive spiritual stage of evolution to show that these brain mechanisms evolved first in linguistic brains. Even if there were, there might be no dramatic evidence of the difference between these two levels of neurological organization, because the reflective level of part-whole complexity does not require any basically new systems. It requires only higher levels of part-whole complexity in the same systems that constitute naturalistic imagination with its capacity to generate and be controlled by over verbal behavior.

There may, however, be some evidence for this theory about the difference between beliefs and desires in the way different kinds of words are processed in Wernicke’s area. Different regions of neocortex in Wernicke’s area are the locus for words referring to objects in space, such as kinds of animals, and words referring to kinds of behavior, including tools. It suggest that there is a connection between telesensory images of each kind of behavior and behavioral schemata for generating that kind of behavior. This is evidence of a mechanism by which the brain distinguishes between beliefs and desires, that is, between psychological states most relevant to input and those most relevant to output.

There is little danger in proceeding at this point on the assumption that there is a reflective level of neurological organization that can be tried out as a random variation. Given the structure of the faculty of imagination, only rather modest changes are required for the behavior generator to speak psychological sentences and, once again, the details of the nervous mechanism can be acquired by learning.

The origin of the reflective level of neurological organization. The only reason to doubt that the reflective state of evolution is inevitable have to do with its origin, that is, how a simple and weak form of rational imagination tried out as a random variation on linguistic brains could make reflective brains powerful enough to control some new condition for which they would be natural selected.

There was, however, an original function for the reflective level of neurological organization. It comes from a uniquely demanding form of natural selection that primitive spiritual animals eventually imposed on themselves. They waged war on one another. The advent of war meant spiritual animals had to make a new kind of choice between incompatible kinds of behavior. That choice could not be made very reliably with naturalistic imagination. But it could be made much more reliably with rational imagination, even if it were not very reliable and occurred only in the leader of the group. Thus, since the capacity to use psychological sentences was a possible random variation on linguistic brains, it was tried out, and it was quickly selected for controlling an urgent new condition affecting their reproduction. That began a stage of evolution that made the members reflective subjects and eventually gave them the enormous power of reason.

The advent of war. Since the use of natural sentences originally evolved to coordinate individual behavior mainly in hunting animals, it is not surprising that primitive spiritual animals would eventually use it to control the outcome of their interactions with other groups of non-linguistic hominids. The new sources of free energy opened up by the use of natural sentences would eventually be exhausted, because there is only a finite amount of free energy they can use in any region and their reproduction would multiply the number of spiritual animals consuming it. Like all reproducing organisms, spiritual animals would eventually impose natural selection on themselves. But spiritual animals had a new way of overcoming scarcity. They could turn their hunting skills on nomadic bands of hominids, either simply killing them so that they could take over the supply of usable energy in the territory or, perhaps, even preying on them, that is, consuming them for the energy such living organisms contain.

The use of language was the origin of war, because such behavior could not evolve before the use of natural sentences.

War could not be tried out as a random variation by their biological behavior guidance systems. Membership in hominid societies was, like other animal societies, rather fluid. Some exchange of members was normal, if only as an adaptation of the instinct of young primates to mate outside the group in which they are born. When necessary, nomadic hominid bands could accept new members, combine with one other to form new groups, or redistribute members, and fights between single hominids (or between leaders of coalitions) would determine a dominance hierarchy within any animal society. Thus, when resources were scarce and nomadic bands of hominids encountered one another, there might have been fights among individuals, or even among coalitions, but no group would systematically kill off all the members of the other group. Dominance battles do not usually end in death, and since social level behavior was still instinctive, the evolution of violent behavior toward all the members of another group would require the same random variation to occur simultaneously in nearly all the members of some group. Only if they all happened to have the new desire to kill all the members of another group (or to follow their leader in doing so), this social level trait would never be tried out and, thus, never selected. Such a combination of random variations is so unlikely as to be impossible, especially if hominids had the normal inhibition about using other members of their own (or kindred) species as a source of free energy.

No such improbable random variation is required, however, to explain how spiritual animals could behave in such a violent way toward groups of non-linguistic hominids. No changes in their desires would be necessary, because the desire to submit to their leader inclined every member to do his part in the group plan pronounced by the leader. Since the use of a primitive language would enable them all to see how their joint behavior would work together in bringing about a goal they all desired, they could act with the same intention. They had practice in the use of language to coordinate violent behavior from hunting other kinds of animals. They may have felt some reluctance to take such actions against a kindred species, but it could be overcome, at least in times of scarcity, by their disposition to submit to a leader and cooperate in social level behavior, especially if they were starving and the desire for food was intense. Even if they could not bring themselves to eat hominid bodies, they would be motivated by seeing how a plan of attack that killed all the members of the other group would give them access to what food there was in the region.

The use of natural sentences, therefore, made war against groups of hominids inevitable. Though war derived from hunting, it was basically different, because members of hominid bands were disposed to protect one another. They would fight back as best they could, when they had no other option (because as we have seen, individuals on their own were still usually doomed by predatory beasts, such as lions and packs of wolves). But even with the use of tools to fight back, hominids were no match for spiritual animals. They had no defense against attack by a spiritual animal that could adapt the spatial aspects of its social level animal behavior to spatial aspects of the situation in imagination prior to acting. Hominids could be surprised and trapped by the spiritual animal’s capacity to impose a geometrical structure on the motion and interaction of objects in space. (After all, warfare is just a special case of controlling the thermo­dynamic flow of free energy toward evenly distributed heat in the region). Nomadic hominids may sometimes have chosen to run away from their attackers, but even if they survived predation by other animals, that still deprived them of access to the food available by hunting in the region.

The new behavior of spiritual animals was not merely ritualized fighting of the kind that evolves within a species to divide up limited sources of energy in a region. They killed all the members of other hominid groups in order to take over their territory. It was inevitable, when their own reproduction made resources scarce, because war was a new way of controlling this most basic condition affecting their reproduction and it was possible for them. In the end, therefore, their new means of acquiring energy meant the extinction of non-linguistic hominids.

This kind of behavior was not long reserved, however, for use against mere hominid societies. Adapting to warfare gave linguistic animals aggressive desires, like anger and hatred, that made it easy for them to kill animals like themselves. Thus, once all the non-linguistic hominid societies in their region had been wiped out, spiritual animals had enough experience with violence against other groups that, when their own continuing population growth once again made resources scarce enough, some spiritual animals, at least, would try the same means against other spiritual animals. It may eventually have involved yet further changes in the desires they felt towards other members of their own species. But it would not require all the members to try out simultaneously the same random variation, because a leader with a suitable random variation could motivate his followers. Since war again other spiritual animals was a possible means of controlling a relevant condition, reproductive causation inevitably made it actual. That is simply how reproductive cycles of spiritual animals add up in space over time.

War against other spiritual animals was not just predation, for it would usually result in death for all the members of the other group (except possibly some women who were kept alive for other purposes). That was the only safe way for spiritual animals to protect themselves from members of other spiritual animals who were accustomed to cooperating in violent behavior. But there is no reason to rule out cannibalism (if that term applies in this case), because eating the victims of their killing was a possible source of food. Predation was not, however, the original function of war even against non-linguistic hominids. War supplied much more food all at once than could be consumed, and the risks of battle made it more costly than hunting other animals. Furthermore, spiritual animals would have engaged in war, even if they did not eat their victims, since it had the effect of removing competitors for the energy available in the region.

The need for a better behavior guidance system. Though war was inevitable, it was a fateful juncture in evolution. It changed radically the world in which spiritual animals lived. The environment posed a new kind of danger for spiritual animals, and they had to make a new kind of choice between fundamentally different kinds of behavior. Every time they encountered a society of language-using animals like themselves, spiritual animals were forced to choose between war and peace. It was a crucial decision, for if they chose to be friendly toward a group that was planning to kill them, they could all die. But if they chose to war against a society that was willing to be peaceful, they would suffer the losses that such activities involve. Even if they won, the costs would be unnecessary, if resources were not scarce. They could, of course, choose to move out of the way, but that alternative would often mean going without food as others took over the territory from which they had expected to acquire energy.

It was as important for spiritual animals to be able to make this choice correctly as it was for the first animals to choose correctly between ingesting other objects or not — or for the first living organisms to choose between periods of growth and reproduction. In all three cases, choosing between the incompatible alternatives was required for the very existence of organisms of their kind. A wrong choice could mean the end of their reproductive cycles. In short, spiritual animals needed a behavior guidance system in the same sense that living organisms needed a biological behavior guidance system and heterotrophs needed an animal behavior guidance system. Spiritual animals already had a behavior guidance system for their social level animal (and biological) behavior. It was the use of a primitive language, and we have seen how it is a unique spiritual structural cause of their social level behavior. Since the animal behavior guidance system primitive spiritual animals already had was inevitably the locus of further evolution changes, it would take on the new behavior guiding function of making choices about war and peace.

What makes this possible, as we shall see, is a higher level of part-whole complexity in the linguistic representations (due to a higher level of neurological organization) that were used to coordinate the members behavior to act on other objects as a whole. That gave them the capacity for reflection, and since that is the mechanism of reason, reason might be called a new kind of behavior guidance system, with the function of making choices about war and peace.

But reason takes over the function of guiding the animal and biological behavior of spiritual animals, and thus, it is basically the same behavior guidance system that make spiritual animals possible in the first place. And since the higher level of neurological organization occurs within the spiritual animal’s behavior guidance system, the evolution of reason is more like the evolution of higher levels of neurological organization in the subjective and manipulative animal behavior guidance systems. In both cases, is a substantial increase in the power of the animal behavior guidance system. Thus, choices about war and peace will be treated as just a new kind of choice that is made by the spiritual animal’s behavior guidance system, much as it also found itself making biological choices, about growth and reproduction, for the beginning.

To be sure, it would not always have been difficult to make the right choice. There was no need to think twice about any remaining nonlinguistic hominids they may have encountered when resources became scarce. And as long as there were plenty of resources, spiritual animals could live at peace with one another — perhaps, under favorable conditions, for many generations of population growth.

Moreover, some other societies, at least, could be assumed to be friendly, for they were closely related biologically. Nomadic bands had to divide when their populations became too large to gather enough energy by wandering around, and individuals from such groups would recognize one another. Sometimes they would have strong attachments, which would lead them to treat members of other groups like members of their own group. And mating would give them a motive to maintain friendly relations with at least some other groups. They had inherited the primate instinct of mating outside the group, and it would continue to be naturally selected because of the advantages of avoiding inbreeding. However, since animal predators made it dangerous for solitary animals to travel alone, mating would take the form of exchanges of members between friendly groups that encountered one another.

There were, however, other spiritual animals around that would wage war on them. Thus, when they came upon other members of their own species, spiritual animals would inevitably make a distinction between Us and Them. It marked a fundamentally different attitude toward members of other groups, for those who were one of Us would be of the same “tribe” and would be treated in a friendly way, like other members of their own group. But members of nomadic bands from other tribes would be treated like groups that were (or might be) at war with them.

Furthermore, war was an extremely strong form of group level natural selection, which would adapt individuals more basically to membership in spiritual animals. War was dramatically different from the group level natural selection imposed on nomadic bands of hominids, for that was imposed by the habitat that primates invaded. Hominids had to travel in groups in order to protect themselves from the great predatory animals of the grasslands. Though hominid bands eventually imposed natural selection on themselves by the scarcity caused by their own population growth, group selection was not very strong, because not all their members died when times were hard. Survivors could join other groups or form new groups, as many other social animals do. With the advent of war, however, it was more common that all the members of a society would die at once. And even if some members were not killed, it would not be easy for language using subjects to move from group to group, at least, not when they used different languages.

The advent of war would, therefore, cause changes in the desires of the language using primates who adapted to it. They would evolve a pair of strong, but opposite desires, mirroring the choice forced on them by their spiritual nature. One would make them protective of members of their own group and members of others whom they recognized as one of Us, whereas the other desire would make them capable of aggression toward members of groups who were one of Them. One desire would draw them together, and the other would put them at odds with one another, making them suspicious and capable of brutality. Both desires would be strengthened by group level selection, since groups that lacked either desire would tend to be wiped out by losing in war. Thus, linguistic animals evolved desires that made them capable of both kinds of behavior involved in the choice of their spiritual nature forced to make.^xl

With strong desires to behave in opposite ways toward other groups, a choice between them had to be made every time one spiritual animal encountered another. Most of the time, there were at least some other groups around they recognized as members of their own tribe. And in peaceful regions, for example, where sources of energy had been divided up into territories, there was probably some warning of the arrival of bands of language-using primates who would wage war against them, so that they could be on the look out and prepared to fight. Between these extremes, however, the input for the choice they had to make was limited and unreliable.

Some distantly related spiritual animals might be given the benefit of the doubt because of their language. Language would be the main criterion for tribal membership among primitive spiritual animals, since the sounds, vocabulary, and surface grammars used by a language are conventional. And spiritual animals from the same tribe would normally be treated as one of Us.

However, spiritual animals from other tribes would be fair game — and, by the same token, quite dangerous. The more remote the relationship, the greater the danger, for it would be difficult to tell whether another group was of the same tribe. Even nomadic bands from the same tribe could be dangerous in special circumstances, such as times of extreme scarcity or when a string of easy victories made a group feel invincible.

And there would be spiritual animals about which they could not be sure. Some spiritual animals might happen on the trick of speaking the language of nomadic bands in the territory so that they would be treated as members of the same tribe and recognized it as a means to victory at war.

The behavior guidance system of spiritual animals had, therefore, to take on a new behavior guiding function. Spiritual animals had to choose between war and peace. That choice was forced on them by their own means of acquiring energy. It was a fateful decision, because choosing either war or peace in the wrong situation was a costly mistake. But in primitive spiritual animals, the choice was made in an animal-like way, by the relative strength of opposite desires, on the basis of whatever cues had evolved or been learned as triggers for those desires. Even when there was time for a leader to hear what everyone had to say, this behavior guidance system was liable to disastrous errors. They needed a more reliable way of making the basic choice entailed by their spiritual nature.

The nature of reflection. As linguistic animals, however, the need for a better way of choosing about war and peace could be met by a mechanism that enabled spiritual animals to “see into the minds” of other spiritual animals. Which kind of behavior would control the condition affecting their reproduction in the situation depended on the plans of the other spiritual animal. If the other spiritual animal was intending to wage war to control the territory and its resources, it would be necessary to fight or get out of its way. The worst mistake would be to take the other spiritual animal to be friendly when it is planning war. On the other hand, if the other spiritual animal had peaceful intentions, it would be better, considering the costs, to avoid war, although fighting might still be chosen in order to protect or gain territory from which to gather energy. In any case, to make the correct choice more reliably, it would have to be able to peer into the mind of the other spiritual animal and see the plans behind their behavior.

All any spiritual animal had to go on, however, was the observable behavior of the other spiritual animal. The animal system of representation had been shaped over eons to be maximally powerful in detecting physical aspects of objects. That would make them aware of the bodies making up the other spiritual animal, of their behavior and motion in space, but it would not always reveal what they needed to know about the other spiritual animal’s plans. To be sure, observation would sometimes make the choice obvious, for example, when they saw victims of a newly arrived group whom they recognized as belonging to their own tribe. Or when they were already under attack by the other group. But what members of the other group said, especially if said to them, would not necessarily be a trustworthy guide to the intentions causing their behavior. It might be disastrous, since the advantages of deception could be discovered by trial and error. But often they would not even be able to understand the others’ language.

It was nevertheless possible, in principle, to discover the other spiritual animal’s intentions from their behavior, for there is a regularity about social level behavior generated according to a plan of group action. What members of the other group do at one moment is part of a geometrical structure in time and space, and part of it is how they will behave in the future and how they would behave in certain situations. That is, after all, how social level animal behavior structures the thermo­dynamic flow of free energy toward increasing entropy to make things happen that would not otherwise happen.

If it were up to their naturalistic imagination by itself, the spatio-temporal geometrical structure about their behavior might be too complex or too subtle to be recognized. But this challenge could be answered. There was a way for them to recognize the pattern, because such behavior is guided by the same kind of structural cause as their own. By identifying the causes behind the other spiritual animal’s behavior, they could anticipate the parts of the spatio-temporal structure yet to come.

The mechanism responsible for this remarkable insight is basically the ability to use a language with psychological sentences, as well as natural sentences. We have seen how this higher level of neurological organization gives the linguistic brain a new form of imagination, rational imagination, by which they can think about psychological states and understand how they cause behavior (and beliefs). “Reflection” is an appropriate name for a mechanism that enables animals to use their own behavior guiding processes to simulate the behavior guiding processes going on in others.

Rational imagination can be used to explain or predict the behavior of subjects in any situation. Several psychological images may have to be predicated of the subject to represent all his relevant beliefs about the situation he is in and the various desires (or longer range intentions) that are at work in him, but they can all be held together as parts of the psychological image that is being predicated of a subject in the (perceived or imagined) local scene. They are all imposed at once as a temporary modification on one’s own worldview and goals, as if one were in the other’s situation. The changes that occur in one’s beliefs or intentions are the predictions one makes about the other subject, given those premises. The conclusions may be just inferences about what the subject would come to believe. But when it leads to new intentions, it is a prediction of the subject’s behavior.

To serve the function required by spiritual animals, however, rational imagination would have to take a somewhat different form. As suggested at the beginning, what is known is the overt behavior of the members of the other spiritual animal. Along with common background beliefs, they are assumed to have whatever additional, relevant beliefs that come from where they are located in the territory. In order to predict their future behavior, it is necessary to work backwards to their common intention by comparing possible sets of desires and beliefs and the intentions to which they would lead, for it is basically an inference to the best explanation of what is known. Thus, rational imagination would enable reflective subject to tell more reliably what they should do about war and peace.

Since being able to see into the minds of other spiritual animals would serve the urgent function of making correct decisions about war and peace more reliably, it would help control the condition that affects their reproduction so dramatically. Thus, the revolutionary change that begins the reflective stage of evolution is inevitable.

The evolution of rational spiritual animals on earth. Three evolutionary stages have been mentioned in this explanation of the origin of spiritual animals. The first was the evolution of animal societies of hominids; the second was the evolution of primitive spiritual animals; and the third was the evolution of rational spiritual animals.

Here is a brief review. (See the diagram of stages of evolution.) Although the first stage (stage 7) is just part of the radiation of primates, both subsequent stages require higher levels of part-whole complexity in the behavior guidance system than the previous stage. Each stage is predicted by the further relevant condition that a higher level of part-whole complexity enables the primary structure to control, though the evolution of primitive spiritual animals (stage 8) also involves a higher level of biological organization as well. The use of natural sentences evolves in hominid societies, because that makes it possible to generate social level behavior as the result of a shared intention in which different members make different contributions to a common plan. But since as population grows and resources become scarce, they use war to obtain energy, spiritual animals live in a dangerous world where another behavior guidance system is needed to make the momentous choice between war and peace. The use of psychological sentences evolves (stage9), because it makes explicit the reference to psychological states that is implicit in the input to the rational behavior guidance system. The choice between war and peace depends on the intentions of the other spiritual animals, and rational imagination enables them to represent psychological states as causes of behavior (and beliefs). The ability to infer the intentions of other spiritual animals from observations of the behavior of their members — that is, to see into their minds — makes it possible to choose between war and peace earlier and more reliably than primitive spiritual animals. Thus, these stages of evolution are inevitable, if evolution is the global regularity about change over time caused by how reproductive cycles add up in space over time, as we have found holds necessarily in a world of matter and space in time.

All three evolutionary stages are inevitable, but it is not clear from the data accumulated by paleontology and archeology which species are at which stages. Between hominids (stage 7) and reflective subjects (stage 9), there are linguistic subjects, or primitive spiritual animals (stage 8). The first and last of these stages are relatively clear. But it is not entirely clear when spiritual animals first evolved, and thus, neither is it clear when they first became rational.

If reason explains human nature, the third of these three stages, rational spiritual animals (stage 9), is represented by Cro Magnon Man (modern humans or Homo sapiens sapiens), because apparently nothing basic distinguishes us from them. Cro Magnon Man is the species that replaced Neanderthal Man (archaic humans or Homo sapiens) in Europe about 35,000 years ago. Not only are they anatomically indistinguishable from modern humans as far as fossils reveal, but judging by the wealth of artifacts that remain, ranging from finely chipped stone tools and weapons to jewelry and works of art, they also had a rich culture, like modern humans.

We have considered the possibility that Homo erectus had the use of a primitive language of natural sentences, but as we have seen, it is by no means required to explain what is known about them. And there is much to suggest that they were merely exploiting the limited capacity of animal cries and screams to serve as signs in coordinating behavior, comparable to wild dogs of Africa, except that they had new kinds of behavior make possible by structural imagination.

In archaic humans, such as Neanderthal Man, by contrast, there is evidence of a dramatic change in both the tools used and the capacity for verbal behavior. Flint tools and hafted stones indicate that archaic humans had a more advanced (Mousterian) culture, as we would expect of animals with the greater understanding of causal connections that comes with having a conception of states of affairs. There is also fossil evidence of changes in the larynx that suggest a much increased reliance on highly modulated sounds. Moreover, if archaic humans did have a primitive language of natural sentences, their capacity to coordinate behavior would explain why Homo erectus became extinct about the time that Neanderthal Man and other species of archaic humans showed up. That is, Homo erectus were the societies of hominids on which archaic humans preyed, before they took up war against one another.

Thus, it seems likely that that archaic humans were the first spiritual animals (stage 8). Given the ontological cause of revolutionary evolution, the replacement of Neanderthal Man by modern humans was inevitable, because Neanderthal Man would have to make choices about war and peace like animals, acting on the strongest immediate desire caused in the leader by instinctive or learned cues. Without the capacity for reflection, they could not see into the minds of other spiritual animals.

Neanderthal Man had occupied Europe since at least 200,000 years ago, but even though they had robust, muscular bodies, they were wiped out by slighter-bodied Cro Magnon Man within a few thousand years about 35,000 years ago. Warfare is an extremely strong form of group-level natural selection, and it would have given Neanderthal Man a great facility at the use of natural sentences. But if they were only primitive spiritual animals, they would be no match for the invaders, because without the use of psychological sentences, they could not figure out the intentions of Cro Magnon Man. On the other hand, Cro Magnon Man, as rational spiritual animals, could see into the Neanderthal mind. Thus, not only could they defend themselves against Neanderthal attack, but they could also intentionally deceive or trick Neanderthals, for they could understand the linguistic and other instinctive signs Neanderthals used to tell friend from foe and turn them to their own advantage.

It might be argued that Neanderthal Man and Cro Magnon Man cannot represent successive stages in the evolution of spiritual animals, because Cro Magnon Man could not have evolved from Neanderthal Man. There is some evidence (from their mitochondrial DNA) that modern humans had a common ancestor in Africa about 200,000 years ago or more, about the time archaic humans, such as Neanderthal Man, evolved. Furthermore, there is evidence of modern humans existing side by side with Neanderthal Man (archaic humans) in the Middle East some 90,000 years ago, long before their invasion of Europe, and the remnants of their technology at the time indicate roughly the same level of culture as Neanderthal Man.

These objections are not, however, decisive, because it is not necessary for Cro Magnon Man to have evolved from Neanderthal Man for them to represent a later stage of evolution. There were probably several species of archaic humans in existence 200,000 years ago, not only Neanderthal Man, but also other species of spiritual animals, and one of those others could have been the ancestors of modern humans. Since they must all have had the use of natural sentences, what made the ancestors of modern humans different may have been something about their neurological mechanism for using natural sentences that made it easier for them to try out the higher level of part-whole complexity required for the use of psychological sentences. Thus, the somewhat greater brain size of Neanderthal Man (about 1500cc on average, as op­posed to 1350cc for modern humans) may indicate, not greater intelligence, but just a more cumbersome mechanism for using natural sentences.

Furthermore, it is possible that reason had already evolved 90,000 years ago, when both modern humans and archaic humans existed side by side in the Middle East, because this was during the last great ice age. The robust bodies of Neanderthal Man were well adapted to the harsh climate in Europe, whereas modern humans, with slighter bodies, were confined to the more temperate region of the Middle East. Thus, the greater capacity of rational spiritual animals to make choices about war and peace may have been used almost exclusively to kill Neanderthal Man only when Neanderthal Man ventured into their more energy-rich territory.

Indeed, the presence of Neanderthal Man may have enabled modern humans to live at peace with one another, because at those times when resources became scarce and war was a means of expanding the supply, modern humans could increase the territory from which they gathered energy by waging war against archaic humans, rather than against other modern humans. Modern humans may even have hunted archaic humans for food. In any case, the balance between archaic and modern humans could have been maintained for many thousands of years, because as long as the ice age continued, modern humans were unable to invade very deeply the territory occupied by Neanderthal Man. Thus, their radiation would have been stymied, like mammals who could not dislodge dinosaurs from the rich ecological niches to which they had become well adapted.

This would explain why Cro Magnon Man replaced Neanderthal Man suddenly 35,000 years ago, for there was a brief respite from the last great ice age at that time, which lasted for a few thousand years. The change in climate enabled modern humans, for the first time, to overcome the scarcity caused by their population growth by invading Neanderthal territory, and their greater skill at making war meant the extinction of Neanderthal Man.

That is, it would be analogous to the extinction of the dinosaurs. Although dinosaurs were so well adapted to their energy-rich ecological niches that they were invulnerable to invasion by mammals, the impact of an asteroid changed the environment so radically that dinosaurs and mammals had to complete in a new environment, and the inherent superiority of subjective to telesensory animals made it inevitable that mammals would replace the dinosaurs. In a similar way, Neanderthal Man was invulnerable to replacement by modern humans until a break in ice age occurred and modern humans could take advantage of their inherent superiority to invade Neanderthal territory and replace them. Then, when the ice age returned a few thousand years later, Neanderthal Man was already gone, and modern humans could learn how to survive in the colder climate without competition from archaic humans. On this account, therefore, the sudden appearance of Cro Magnon Man in Europe about 35,000 years ago would be just another instance of catastrophic changes “shaking out” the natural kinds of organisms according to their inherent superiority.

Cro Magnon culture differed from Neanderthal culture in just the ways that we would expect reflective spiritual animals to differ from primitive spiritual animals. As rational animals, they could not only see into other minds, but also reflect on the causes of their own conclusions about how to behave and what to believe in the process of drawing them. Thus, instead of a language of just natural sentences for coordinating behavior and passing technology on by imitation, the culture passed down from generation to generation by Cro Magnon Man was an accumulation of arguments about what to do in certain situations and what to believe (as will be explained more fully in the next section). And their culture would reflect the danger of living in a world where war was always possible.

Once Neanderthal Man was no longer around to prey on, it was inevitable that modern humans would resort to war against one another, since the growth of their population caused scarcity and they knew the value of war from battles with Neanderthal Man. But when reflective spiritual animals turned the weapon of war against one another, they had to determine, as primitive spiritual animals did, whether other groups they encountered were of the same tribe, for there were normally at least some other groups with which they had friendly, in-group relations. Tribal membership was the main way of telling whether other groups they encountered were one of Us or one of Them in choosing between war and peace, but tribes of reflective spiritual animals were based on sharing a culture of accumulated arguments, including legends and myths, rather than simply use of the same language. But when they decided to treat the other group as part of their tribe, they made themselves vulnerable, and thus, there was always the danger that other groups were gaining an advantage over them in war by pretending to share their culture. This was a trick that had probably worked well against Neanderthal Man. By pretending to speak their language of natural sentences, primitive spiritual animals would have been deceived into treating their enemies as friends. More subtle forms of deception might be used against other rational spiritual animals.

The danger of war would explain, therefore, the sudden appearance of highly refined artifacts, such as the ivory figures of animals which were apparently worn as jewelry, after Cro Magnon Man invaded Europe. It would provide credible evidence of their tribal membership. Groups in a tribe might identify with different kinds of animals, and thus, tribal membership could be represented by groupings of animals and, within tribes, nomadic bands could keep track of their relationships to one another by passing down stories about the animals with which they identified from generation to generation. Groups could give credible evidence of which group they were and which tribe they belonged to by the kinds of animals depicted in their jewelry. The ornaments were credible, because the art involved in creating them made it too difficult to fake them. Thus, highly refined works of art were good evidence about one another’s tribal membership, and that made it easier for groups from the same tribe to establish trust. Considering their value in making reliable choices about war and peace, there was a strong selection pressure at the group level, favoring skill at art as well as facility in the use of psychological sentences to reflect on the reasons for their behavior.

In other words, the lack of highly refined ornaments and ivory figures among the remnants of modern humans in the Middle East around 90,000 year ago does not necessarily mean that reason had not yet evolved. Their level of culture is what might be expected of rational beings, if warfare was reserved for use against the easily recognized archaic humans that were always on the frontier of the territory from which they were excluded by their slender bodies. Under the circumstances, all modern humans may have been able to treat one another as part of the same tribe.

What ontological philosophy implies about the evolution of reason is, therefore, consistent with what is known about the ancestry of human beings on Earth. Indeed, it accounts for those facts better than the theories currently being discussed by archaeologists. But it should be emphasized that ontological philosophy would not be refuted by evidence that contradicted the interpretation of the archaeological evidence that has been sketched here. It is also compatible with the hypothesis that modern humans in the Middle East some 90,000 years ago simply had not yet evolved the use of psychological sentences. It is, however, an empirical question which species on Earth are the ones that represent those stages. All that we know on ontological grounds is that there must have been a stage of evolution between societies of bipedal hominids and rational animals, because reason can evolve only in primitive spiritual animals, which already have the use of natural sentences. No one denies that societies of hominids are a late phase in the radiation of higher primates (stage 7). Nor does anyone doubt that Cro Magnon Man was a form of modern humans, and if the nature of reason as explained here accounts for human nature, Cro Magnon Man must represent the rational spiritual stage of evolution (stage 9). Thus, it remains only to decide which species represents primitive spiritual animals (stage 8). On the basis of what is currently known about our past, I have suggested the reasons for believing it is represented by Neanderthal Man and other archaic humans. But new evidence might justify assigning this role to another species.

Cultural evolution at the rational spiritual stage. Gradual evolution during the rational spiritual stage gives individual humans greater facility in using psychological sentences, but the change that inevitably occurs during this stage is not limited to traits that depend on the biological behavior guidance system.

The use of a language with psychological sentences transforms linguistic interactions into an exchange of arguments. As variations on arguments are tried out more or less randomly, the many individual judgments about which of competing arguments to accept is a rational selection from among them, and so the arguments accumulated in a spiritual animal and passed on from generation to generation evolve. Culture undergoes a gradual change in which arguments start off simple, uniform and weak and become increasingly complex, diverse and powerful.

In other words, cultural evolution is a form of reproductive causation contained within spiritual animals. But since it involves the rational selection of random variations on arguments, culture tends to discover the true, the good and, as we shall see, the beautiful.

In order to show that cultural evolution is part of the rational spiritual stage of evolution, I will explain how cultural evolution is a form of reproductive causation contained by rational spiritual animals. But instead of trying to trace the entire course of cultural evolution, I will show how the natural perfection toward which rational level culture evolves inevitably includes three dichotomies that divide arguments into four groups, without only religion to paper over the differences among them.

Reproductive causation contained by rational spiritual animals. Cultural evolution is a reproductive global regularity that occurs in spiritual animals. The reproductive cycles and the space in which they add up over time are constituted by rational spiritual animals. Thus, the essential nature of rational spiritual animals contains the ontological cause of this gradual evolutionary change. It depends on the relationship between their social and cultural aspects.

To recapitulate, reason evolved in spiritual animals that already had the use of a primitive language. Language is what gives a group of multicellular animals the structural cause needed to coordinate the members’ behavior as social level behavior, and made spiritual animals a new form of life on the social level of biological organization. But language worked so well, as we have seen, that it eventually forced spiritual animals to choose continually between war and peace. That choice was to made more reliably with the use of psychological sentence evolved, but that made the individual members reflective, so that their behavior was caused by reasons. Reason became the system for guiding not only the behavior of the spiritual animal, but also individual behavior.

The unique way that the individual and social levels of biological organization are combined in rational spiritual animals makes it possible for reason to evolve more and more power to control conditions in the world. The structural cause of social level behavior in spiritual animals is a special kind of material structure which I am calling a “spiritual structure.” A spiritual structure is actually two different kinds of structures bound together by the use of language, one under the social aspect and the other under the cultural aspect, and both are structures of the spiritual animal as a whole.

The structure under the social aspect is the fact that language-using animals stick together and are in continual interaction (including linguistic interaction) as parts of an organism at the social level.

The structure under the cultural aspect includes all the linguistic structures generally shared by members and which individual brains born into the spiritual animal normally acquire, including the language itself and the set of beliefs and intentions that come to be shared by its members because of the various linguistically mediated ways they normally interact.

Since the structures under these two aspects of the spiritual animal are different, they can interact with one another.

Thus far, we have focused on how the linguistic structures under the cultural aspect affect the social aspect. In primitive spiritual animals, the use of language distributes plans of social level behavior to the members in a way that enables each individual to know what he is supposed to do, and that makes it possible for the social level behavior of spiritual animals to act on other objects in space (or organize interactions of its own members as social structure). More generally, language enables the members to share beliefs and intentions as a worldview, and culture generates customs, institutions and other regular aspects of social level behavior.

There is, however, an equally important effect that the structure under the social aspect has on the cultural aspect, because the linguistic interactions can affects the content of the linguistic representations being exchanged among the members and, thus, their beliefs and intentions. Though this effect already occurs inefficiently in primitive spiritual animals, it becomes, with the evolution of psychological sentences, a normal part of almost linguistic interactions. In rational spiritual animals, as we shall see, the linguistic representation exchanged include arguments (that is, conclusions about how to behave or what to believe that come together with reasons for them), and such an exchange constitutes another contained form of reproductive causation, this time, one in which the arguments accumulated as culture evolve in the direction of natural perfection for arguments of its kind, which is to discover the true, the good and the beautiful, albeit within certain inherent limits.

In primitive spiritual animals, the social aspect already has important effects on the cultural aspect. The linguistically mediated interactions among the members is what distributes the plan among the members in a way that assigns them different roles to play in social level behavior. But linguistic interactions were not necessarily as one sided as that model suggests.

Guiding social level behavior was not necessarily just a matter of following the leader’s instructions. Members could also pool their knowledge of the current situation, since everyone could speak natural sentences as well as understand them. The context and manner of the utterance would make it clear whether the sentences were meant to assert a description of what is, to ask about a state of affairs, or merely to present a possibility to be taken into consideration.

Members could also pool their understanding of efficient causation in the natural world, since naturalistic imagination gave them all the capacity to see states of affairs as causes and effects. Thus, spiritual animals could accumulate increasingly complicated techniques for controlling natural processes. For example, instead of carrying fire with them, they could acquire the skill to start fires when needed.

Finally, since each member could understand how the leader’s plan was supposed to attain goals set by their own desires, their willingness to follow his instructions would tend to depend on whether it made sense to them. The adoption of a plan for the immediate situation would the result of a linguistic interaction between the leader and the members.

In rational spiritual animals, however, this effect of the structure under the spiritual animal’s social aspect on its cultural aspect becomes much stronger, because context is no longer needed to indicate the roles that spoken sentences are meant to play in determining beliefs and behavior. The use of psychological sentences enables them to represent psychological states as causes in the process of guiding behavior (or determining beliefs), and that makes it possible for speakers, in their attempt to agree about what the spiritual animal should do, to make explicit what roles they mean their sentences to play. A leader is less important to the spiritual animal’s behavior guidance system , because every member can make arguments at any time that everyone can understand.

The exchange of arguments in spiritual animals is the ontological cause of cultural evolution. Arguments are like “organisms” that reproduce as one member of a spiritual animal makes the argument and another member accepts it as a cause of what she believes or does. Such reproductive cycles add up in the “space” of spiritual animals over time to a form of natural selection. They cannot go on reproducing for ever, because there are only so many members of a spiritual animal. But since what determines which one’s go on is, as we shall see, rational selection, the arguments accumulated as culture in a spiritual animal gradually evolve in the direction of natural perfection for “organisms” of their kind, that is, arguments that discover the good and the true.

In order to show the inevitability of this global regularity within rational spiritual animals, let us consider the nature of arguments and the nature of rational selection. That will enable us to see why gradual cultural evolution is inevitable.

The nature of arguments. Though the original function of reflection was to control a condition affecting the reproduction of whole spiritual animals, it is the members who had the faculty of rational imagination, and so it was inevitable that individual subjects would also use reflection to see into one another’s minds and to understand the causes of their own behavior.

Self-reflection. Reflection is self-reflective when psychological sentences are used to predicate psychological states of oneself, instead of another subject. It may be, in the first instance, just a way of monitoring one’s beliefs and desires, which enables one to report how things seem, that is, that one has a certain belief, rather than just making an assertion about the world. Or to recognize that one has a desire, rather than just asserting that something is good. The faculty of rational imagination is required for self-reflection, because that is what enables one to see psychological states as psychological states, rather than simply to have them.

The developmental stage at which children acquire the use of a faculty of rational imagination has been identified in children.^xli It is manifested as the capacity to think about subjects as subjects. Until about the age of three, children cannot distinguish how something appears from what they believe it is. When they mistakenly believe that a molded piece of wax is an apple and they are shown their error, they correct their belief, but they insist that they always thought it was a piece of wax and assume that everyone else will also see it as a piece of wax. By the age of four or five, however, children can understand that it appears to be a piece of fruit, even though they realize it is not, and they expect that seeing it will cause others to form mistaken beliefs about it. The difference is that the older child has the capacity to think about people as forming beliefs because of how things appear in perception, and thus as having beliefs that may differ from what really exists. To be sure, three-year-olds are already able to use such words as “see” and “believe.” But they assume that what is seen or believed is always the same as what really exists, as if there were no distinction between appearance and reality.

The cognitive development of children recapitulates the change that occurred in the evolution of primitive spiritual animals into rational spiritual animals. A whole new range of facts about the world comes into view with the capacity to think about subjects as having psychological states. They include facts about desires as well as beliefs. Instead of simply having desires or seeing objects as desirable, the reflective subject can think of individuals as having desires, whether or not the objects are desirable or attainable, and see their behavior as being caused by them. That is, after all, what was crucial in the original function of reflection, making choices about war and peace.

Self- reflection is not, however, just the capacity to monitor one’s psychological states. In representing one’s psychological states to oneself as psychological state, self-reflection represents them as causes, and that changes the nature of the causes of one’s behavior and beliefs.

Rational imagination enables subjects to see the difference that having any perception, belief, desire or intention would make in the choices they make (or on the beliefs they form). By seeing actual psychological states against the background of what is possible, subjects are able to represent the causes of their own behavior (and beliefs) as causes of their behavior in the very process by which they are causing behavior.

But as rational spiritual animals evolve, that self-reflective power becomes a integral part of the animal behavior guidance system, so that reflection on the causes of one’s behavior (or beliefs) makes a difference in what one does (or believes). That is, the causes of behavior become causes that are represented as causes of behavior as a causally relevant part of the process of causing behavior. That is how they earn the special name. “reasons.” Though reasons are still efficient causes of behavior, their power to cause behavior comes to depend on them being represented as causing behavior.

Reasons. The transformation of animal causes of behavior into reasons makes animals more powerful, because when the causes of behavior must be represented as causes in order to cause behavior, the mechanism that represents them (the linguistic system of representation) can control behavior. That is, it brings the animal causes of behavior under the control of a higher level behavior guiding process. That higher order process is located in the linguistic hemisphere of the forebrain, and we have already seen how the linguistic system of representation acquired control over the causes of behavior.

Even hominids had a desire to submit to the leader, which derives from the dominance hierarchy of animals. But with the evolution of language, the desire to submit to a leader became the desire to do what the leader said, that is, to conform one’s behavior to a linguistic representation of it. Thus, when the use of psychological sentences transformed the members into reflective subjects, the desire to submit to a leader became a desire to submit to reason (that is, to act only when the causes of behavior are represented linguistically in a certain way in the process of causing behavior).

This evolutionary transition is recapitulated in human beings at adolescence. Though the child submits to the plan imposed by her parents, a radical change takes place at puberty. The adolescent starts to take control of his own behavior, often rebelling against parental limitations, because what is causing his behavior are now causes represented linguistically in a different way, namely, as the conclusions of practical reasoning. The burden of being responsible for his own choices takes the form of worries about his identity. This is the process by which the language-based power of reason, which is located in each individual, takes over control of individual behavior.

As will be explained more completely later, this rational control of behavior gives the individual increased power to control relevant conditions. It is a kind of “autonomy” that subjects have because they are rational, or the “autonomy of reason.”

Once the reflective subject has the ability to act on the results of such a reasoning process, psychological states are not merely causes of behavior on which the subject can reflect, but rather a new kind of cause of behavior. For example, though desires are seen as causes of one’s behavior, the capacity to represent the causes of one’s behavior as causes in rational imagination makes it possible to reflect on all one’s desires, including those that will be felt only in the future or under other circumstances. Thus, it is possible to figure out the best way to behave in, say, a series of situations to satisfy them all. This is a form of practical reasoning, and in rational subjects, reason wrests control of behavior away from the animal causes of behavior (mainly, desires), because the desire to submit to reason enables the intention formed by practical reasoning to generate behavior even when it is opposed by currently strong animal desires. Rational subjects can, for example, delay gratification. Nor is this the only way reason guides behavior independently of strongest (other) desire at the moment, for as we shall see, reason even enables the subject to pursue goals that do not control conditions that affect his own reproduction and to do what is good for the spiritual animal.

Reasons can also change the way that beliefs are formed. Beliefs are most commonly caused by perceptions. But beliefs are all connected (because the objects they are about are all related in space and it is possible to call up the states of affairs in which they are involved from the map of one’s territory built up by spatial imagination). Furthermore, episodic memory for particular past events (another form of the capacity to record memory groups in sequences) sometimes makes it possible to reflect on the perceptions that caused particular beliefs. Thus, by reviewing the reasons for one’s beliefs, comparing the relevance of current perceptions with past perceptions in causing beliefs, and the like, it is possible to correct errors and make more reliable judgments about what is true. For example, by knowing which beliefs were caused by perceptions in the past, it is possible to dismiss current perceptional illusions or to resolve ambiguous perceptual input.

Reasons and conclusions. When behavior and beliefs are caused by reasons, the social aspect of the spiritual animal has a much more powerful effect on the cultural aspect, because the linguistic representations being exchanged can contain conclusions together with reasons for them, that is, arguments.

This is the change in the behavior guidance system of the spiritual animal that was suggested above by contrasting the primitive spiritual animal’s use of a leader to distribute a plan publicly to all the members and a processes in which members come to agree about which plan is best by arguing with one another about it. The increased power of linguistic interactions to coordinate the members’ behavior comes from how the use of psychological sentences frees reasoning about what to do (or believe) from dependence on the context provided by a leader.

This change resembles the earlier transition from nomadic bands of hominids to primitive spiritual animals, where the increased power of linguistic interactions to coordinate the members’ behavior came from how the use of natural sentences freed the primate cries and screams from dependence on context for their meaning. In both cases, context was no longer needed to align imagination in different animals, because verbal behavior included grammatical markers that represented how the listener was to operate his imagination. Not only was a leader not needed, but members could be drawn into agreement anywhere about how to behave (or believe) in any situation. That increased the power of spiritual animals in a more far reaching way, because eliminating the need for context in arguing made it possible for arguments themselves to accumulate as part of the culture and, thus, for culture to evolve by rational selection.

Arguments are simply conclusions about what to do (or what to believe) that come together with reasons that recommend them, that is, with other propositions asserted as causes for accepting the conclusions.

The mechanism by which reflective subjects can consider arguments is implicit in their ability to use psychological sentences. The behavioral schema for a psychological sentence generates covert nonverbal behavior that operates on images in the sensory input system. It not only constructs a naturalistic (or psychological image), but also represents it as having a causal role, such as a belief or desire, and predicates that psychological state of a subject. The psychological state is seen against the background of what is possible by rational causation, such as the roles it might play in causing behavior (or belief), and thus, the psychological linguistic act can be used to predict or explain what the subject will do (or believe). This rational explanation can then be expressed in over verbal behavior. For example, “Joe went to the ridge, because he believed that the deer were in the valley beyond and he wanted to check on them.”

Arguments are a modification of this ability to understand rational-cause explanations. When considering the reasons for a conclusion, it makes no difference which rational subject the psychological states are attributed to. Behavior guidance systems all work basically the same way. Everyone shares much the same background beliefs as their worldview. And they are all moved by the same kinds of desires. Hence, the reference to a particular subject as the grammatical subject is generally suppressed in formulating arguments. Thus, arguments are like anonymous rational cause explanations (or predictions).

It is still necessary, however, to include verbs of propositional attitude (or grammatical markers for them) in order to refer to the proposition, rather than what the proposition represents, and to indicate its (causal) role in the argument. For example, “In order to check on the deer, go to the top of the ridge, because they can be seen from there.” The argument must enable the listener to reconstruct the inference in her own rational imagination, and in more complicated arguments, the conclusion may depend on imposing several psychological states on rational imagination simultaneously, or there may be a series of conclusions. Thus, some propositions may be referred to explicitly as reasons for other proposition, or the inference may be indicated by, “and thus” or “because.”

Rational selection. On any given issue, however, there may be arguments for different conclusions. A judgment must be made about which is correct, and it is made by each individual. That is the rational selection of arguments, and as we shall see, that is why the general exchange of arguments among members of a spiritual animal gives rise to the gradual evolution of culture by rational selection.

Judgment. According to this explanation of the nature of the reflective level of neurological organization, each individual is able to judge the correctness of any argument about what to do or believe in any situation, because each has a worldview in which to test its coherence with other beliefs and intentions.

Each individual has a more or less complete set of beliefs about the natural world, because beliefs are all ultimately about objects located in space, and since space is whole, they must all be related to one another in the subject’s mammalian map of his territory. But that is not only to have beliefs about the locations, geometrical structures, and properties that they have been perceived as having, but also beliefs about how they can change locations and how they would interact (since they are objects represented in spatial and structural imagination). And in naturalistic imagination, the worldview also includes the states of objects in space and how they are involved as causes and effects in the natural world. And corresponding to the endurance of the natural world through time, their view of the natural world is a history that includes whatever they remember about the histories of objects in their territories.

Each individual also has a more or less complete set of beliefs about the subjects in their world. Subjects are also objects in space, and though their behavior is explained by their psychological states (as reasons), all the beliefs and intentions by which the behavior of members of their spiritual animal is explained would have to fit together as a whole both in space and over time. Though there is more to be said about it, their worldview would include a social world as well as a natural world, each explained in its own way.

Finally, each individual would has more or less complete set of intentions about what to do in any situation, both at the individual level and regarding the behavior of the spiritual animal as a whole. In addition to any particular plans they may have, it would include intentions about how to choose among goals when conflicts arose. In short, they have certain values.

Though such a worldview is worked out in detail only as far as it was useful or questions about it had to be handled, there is a coherence about the beliefs and intentions it contains, because everything is seen in rational imagination as part of a single world, a natural world of objects in space, including subjects as a special kind of object, where certain basic regularities hold. The worldview is the background against which arguments are tested.

Merely fitting together comfortably with the worldview is all that was required to accept new beliefs about the world, if there is some reason to believe them, such as perception or reports of perception. To report, for example, “I saw deer in the valley,” is to argue, in effect, that it is true for a certain reason, and unless there is some reason to distrust the reporter, it is a good argument. .

Arguments whose conclusions contradict one’s worldview in some way require reasons that can dislodge already established beliefs. For example, in addition to some positive reason for holding the new belief, there may be reasons for doubting the grounds of the old belief. By reflecting on her worldview, it is often possible to surface the grounds for any particular belief by imposing the alternative on imagination and seeing what else would have to change. If those grounds are not themselves well grounded, she may be convinced by the argument.

In some cases, it is possible to dislodge current beliefs by showing that the new belief is entailed by other beliefs that the subject already holds because of regularities to which the subject is committed by the very structure of rational imagination or which are firmly established for other reasons. Or in more complex examples, whole sets of beliefs about some aspect of the world is challenged by an alternative set, and the judgment about which is correct depends on which set was simpler and fit into the background more completely.

The interests of reason. Though each individual judges which arguments to accept, it is not just a whim. Rational subjects judge arguments in the same way, and making rational selection selection in the interest of reason.

Since arguments are tested by their coherence with one’s worldview, their acceptability depends on whether they make one’s worldview more coherent as a whole. It is possible to tell which argument results in the most coherent worldview, because arguments are considered in rational imagination, where the actual (or proposed) is seen against he background of what is possible. Imagination connects all one’s beliefs and intentions together, and so the judgment about whether to accept an argument is ultimately an aesthetic judgment. To use imagination to tell whether one set of beliefs or intentions is better than another is to judge arguments by the beauty of accepting their conclusions, that is, by whether it would be unique among the alternatives in basically the same way as natural perfection itself, that is, making the most out of the least.

Truth. Though the means of judging is coherence, that does not mean that beauty is the goal of reason. Since the foregoing examples are theoretical arguments, that is, arguments about what to believe, the goal of reasoning is truth. The conclusions are accepted because it seems that the propositions correspond to the world. That is how the goal appears to rational subjects, because arguments for believing certain propositions are judged by whether the states of affairs they represent are part of the world as represented in perception and, more broadly, in one’s worldview.

Goodness. There are also arguments about what to do, and in the case of practical arguments, reasons’ goal is to know what is good. But the judgment about whether to adopt the proposed intention urged by the reasons offered depends on how the intention fits together with established intentions about how to deal with the relevant situations. Coherence in this case depends on the intention fitting together with the whole set of intentions, including policies and plans, for dealing with all the situations that arise over time in leading the life of a reflective subject as part of a spiritual animal, and thus, it also requires a judgment based on overall coherence. At this stage of evolution, the intentions are mainly caused by their desires, though as we shall see, that may not be recognized. And since plans for satisfying all their desires depend on an aesthetic judgment, about how they fit together, rational subjects often pursue goals that are good for reasons other than affecting their own reproduction. But established intentions, or values, by which the conclusions of practical arguments are judged are usually seen at the rational spiritual stage as fixed by ancestors, gods, or nature.

Beauty. Truth and goodness are, therefore, interests of reason. But since the truth and the good are judged by rational coherence, reason necessarily has an inherent interest in beauty as well. That is the means that reason uses to judge them, though it may not be recognized as an aesthetic judgment. But the rational interest in the beautiful does guide reason explicitly in other ways, for example in productive reason, that is, in making products that are beautiful, including the fine arts. Since beauty is the same kind of unique optimum as natural perfection, which marks the direction of evolution, there is a sense in which the ancient Greeks were correct in holding that art is the imitation of nature. Art is artificial perfection.

These interests are the interests that rational subjects recognize they are pursuing by reasoning about what to believe and what to do. But given the essential nature that reason has as the behavior guidance system that evolves at the rational spiritual stage, we can see that these interests are actually aiming at maximum holistic power for rational beings, that is, that they contribute to natural perfection.

Though rational subjects may see truth as a correspondence between their linguistic representations and appropriate aspects of the world, they do not understand the nature of the correspondence completely. They take the world to be what appears to them in perception, and thus, they are thinking about a relationship between representations in rational imagination and representations caused by sensory input. In fact, the correspondence that makes the true holds between both of those kinds of representation and aspect of the natural world. But judging the truth of beliefs by the correspondence that seems to hold at the rational spiritual stage usually still has the effect of discovering the actual correspondence, which contributes to the power of the behavior guidance system to guide behavior.

Likewise, rational subjects at this stage see the good as something about what is judged to be good, and thus, once again, reason’s interest seems to be correspondence too. But since the only explanations of the nature of goodness at this stage are religious, it is not clear what practical conclusions must correspond to. From the perspective of ontological philosophy, however, we can see that what correct conclusions about how to behave correspond to is what contributes to the natural perfection of the whole of which they are part. This is not as straightforward as it may seem, for as we shall see, the pursuit of goals may contribute to the natural perfection of rational beings even though they do not control conditions that affect their own reproduction. Because of the autonomy of reason, as we shall see, pursuing goals that are good for other reason, or “optional goals.” is part of the natural perfection of rational beings.

Because rational selection is made by maximizing the coherence of one’s worldview (including intentions), the true and the good are recognized by their beauty in the faculty of imagination. But from our ontological perspective, we can see that even judgments about the beautiful are correct in virtue of corresponding to an aspect of the world. In this case, it is correspondence to natural perfection itself, that is, the state that makes the most of the least. Such optimal states stand out in rational imagination, because that is the ability to see them against the background of what is possible.

Arguments as reproducing organisms. The capacity to argue about anything anywhere, with individuals judging for themselves what is true, means that the linguistic interactions in a spiritual animal constitute a new, contained form of reproductive causation. In this case, what evolves is culture, and it evolves in the direction of knowing the true, the good and the beautiful.

Evolutionary change, in general, is a global regularity whose ontological cause is reproductive cycles and how they add up in space over time. What evolves are material structures that go through cycles in which they not only reproduce themselves, but also do some kind of non-reproductive work. But since evolution depends on a natural selection from those material structures, there must also be variations on them that do different kinds of non-reproductive work, though they all reproduce in the same way, and such variations must continually be tried out randomly. A selection is made by success in reproducing. A selection must be made, because eventually it is not possible for all of the material structures to reproduce. But since which material structures succeed depends on the kind of non-reproductive work they do, evolution is inevitably change in the direction of reproducing structures whose non-reproductive work controls conditions that affect their reproduction.

In the case of biological evolution, the reproducing structures are organisms (or proto-organisms). They impose natural selection on themselves by their own reproduction, because their population increase causes a scarcity of the resources (free energy, if nothing else) in the region needed to go through reproductive cycles. And they evolve in the direction of greater power, because those random variations whose non-reproductive work is best able to promote their reproduction under those conditions are more likely to succeed in reproducing.

We have already encountered one contained form of reproductive causation in tracing the course of evolution. Neurological development is the evolution of behavioral schemata in individual brains by reinforcement selection, and as we have seen, it is change of the brain’s memory groups of neurons in the direction of behavioral schemata that internalize the regularities involved in spatial causation, structural causation, and efficient causation, as well as the words and grammatical structures of natural languages themselves.

Neurological development is, however, only the first the three such contained forms of reproductive causation. The second is cultural evolution by rational selection, and as we shall see, the third is economic evolution by capitalist selection. In each case, evolution is a global regularity caused by how cycles of reproduction add up over time in space, or in the “space” provided by some evolved structure (respectively, the brain, a spiritual animal under its cultural aspect, and under its social aspect).

In the case of cultural evolution, the “reproducing structures” are arguments. Arguments can reproduce, because they can be expressed in overt verbal behavior, making it possible for listener who understands them to be convinced by them. That is, they reproduce themselves in the brain of other members of the spiritual animal. But reproduction is not complete, unless the listener not only understands the argument constructed in rational imagination, but is also convinced by it, because the non-reproductive work of an argument is its effect on how the individual behaves in certain situations or what she believes on certain topics. ^xlii

Random variations on arguments are introduced in various ways. Sometimes reproduction is not perfect, and the argument tried out in the new brain’s imagination is different from that of its proponent. Since they are constructed in rational imagination, variations may be tried out by accident or when trying to think about something else. Dreaming may play a role in generating random variations on arguments, since arguments are constructed by linguistic behavioral schemata and, as we have seen, the function of dreaming in mammals may be to sort out and reassemble parts of behavioral schemata involved in satisfying desires. New arguments can also be introduced when one spiritual animal encounters another, by a process of cultural diffusion. And some variations are likely to be tired out as all the arguments accumulated as the culture of a spiritual animal are passed to the next generation in the process of enculturation.

What corresponds to species of organisms are kinds of arguments. Arguments are differentiated by the situations to which they apply, though there are two classes of situations, one class involving the choice of what to do in the situation, and the other the decision of what to believe on some topic. Thus, arguments of each kind are like a species adapting to its ecological niche, and random variations on each kind of argument compete with one another in each ecological niche, like members of a species with different traits.

As arguments go through reproductive cycles, some reproductive cycles must come to an end. Each brain contains a full set of ecological niches for arguments, at least, in principle, because each individual faces all the situations in which a choice must be made about what to believe and what to do, if only in imagination. But there are only so many brains in the spiritual animal into which they can reproduce themselves. Thus, arguments impose a natural selection on themselves by their own reproduction, in much the same way that population growth makes resources scarce in biological reproduction, because as an argument reproduces into one brain after another, it fills the ecological niche for arguments of its kind. When no member of the spiritual animal lacks a belief or intention for the relevant situation, its reproductive cycles come to an end.

Given the scarcity of brains into which arguments of any kind can reproduce means that variations on arguments of each kind are competing to control the behavior of individuals in each situation. Variations on arguments can be tried out, even when every member already has a more or less complete worldview, because new arguments can be considered in rational imagination, for example, when one member makes the argument to another. To be selected, however, the argument must change the subject’s intentions (or beliefs). That is possible, because arguments include reasons that may dislodge the intentions or beliefs that already fill the relevant ecological niche. Success in reproducing depends on the rational subject’s judgment about which conclusion fits together more coherently in his worldview. That is, natural selection is by rational selection.

Gradual evolution of rational level culture. This is a form of reproductive causation, though it is contained within and sustained by rational spiritual animals, and thus, the arguments accumulated as culture should evolve gradually in the direction if maximum holistic power. As arguments are exchanged in spiritual animals, random variations on them are tried out, and there is a rational selection from among them imposed by the judgment of its members. It is a global regularity because it is a change in the arguments that are accumulated as the spiritual animal’s culture, and what is regular is that they tend to change in the direction of greater power to control the conditions that affect their reproduction. Since the reproduction of arguments depends on their making the subject’s worldview more rationally coherent, culture changes in the direction of discovering the true, the good and the beautiful, which is the source of the power of reason in guiding behavior.

Cultural evolution is not, however, biological evolution. The material structures going through reproductive cycles are just arguments that are expressed verbally by public linguistic representations and can be constructed in rational imagination, where they cause the brain to make an inference, from premises to conclusion. Their rational selection depends on whether accepting them as sound results in a more coherent worldview. Thus, cultural evolution has some unique features and some special limitations.

Like any stage of gradual evolution, arguments start off simple, uniform and weak, and as they evolve by reproductive causation, they become increasingly complex, diverse and powerful. In general, power is likely to increase, because the argument accepted for any given situation is likely to be closer to the truth than the others completing with it. And as situations calling for a choice about what to believe or intend are distinguished from one another, the arguments accumulated as culture become more diverse. Before long, therefore, a worldview evolves with beliefs and intentions for all the relevant situations.

Arguments do not, however, become complex in the same way as reproducing organisms in biological evolution, because arguments are not independent of one another at the ecological level. The ecological niches for arguments are the situations calling for choices about what to believe or intend, and there are similarities as well as differences among such situations. The reasons that hold in one situation are likely to hold in the others that resemble it, and since arguments must often dislodge established beliefs and intentions in order to be rationally selected, arguments that take account of such similarities are more likely to be accepted.

Discovering the true and the good is not, therefore, just a matter of accumulating beliefs about particular facts and making choices about how to behave in particular situations. It also includes the discovery of principles covering entire ranges of situations, uniting the arguments for them. Principles tend to become more general as rational level culture evolves. At a relatively early phase during the rational spiritual stage, for example, principles would evolve to decide which direction is south, where the deer have gone, what caused someone’s illness, who committed the crime, how to avoid hazards of weather, etc. And such principles become subsumed under more general principles as culture evolves.

In more advanced cultures, therefore, whole armies of arguments, with several echelons of command, may confront one another in the battlefield of linguistic interaction within a spiritual animal. There would then be profound theoretical disputes, because both armies, each with many individual arguments serving under a different set of principles, would deal with the same range of situations. Individuals would have to judge which theory would make their world views more rationally coherent, and the disputes may be so deep and global that there is no obvious grounds for choosing between them.

In less disputatious culture, however, principles may evolve without any recognition that alternative principles are even possible. The arguments accumulated in such cultures could become integrated in an aesthetically satisfying way, and yet all of them make the same basic mistakes.

Principles become explicit at the rational spiritual stage for the same reason that subjective animals acquire a general conception of the structure of space and manipulative animals acquire a general conception of geometrical structures. It is a consequence of the neural mechanism that gives subjects a faculty of imagination and how behavioral schemata evolve within it by reinforcement selection.

Arguments are constructed by linguistic behavioral schemata contained in the frontal neocortex, and they use covert behavior to act on the subject’s worldview in much the same way as locomotor schemata use covert behavior to act on the map of the mammalian territory and that manipulative schemata use covert behavior to act on object images within its local images. Covert behavior calls up sequences of images, but the evolution of kinds of covert locomotor or manipulative behavior establishes labels for calling up kinds of sequences of images. With the development of generalized behavioral schemata, particular events would be seen as instances of some kind.