In the last chapter, we were primarily concerned with the idea that there is a way that things are in the world that is independent of our representations of how they are. This view, which I have called “external realism,” is not to be thought of as a theory or an opinion. It is rather a Background presupposition, something that is taken for granted by us when we perform many sorts of intentional actions—as, for example, when we eat, walk, or drive a car. It is also taken for granted by us in large stretches of our discourse, indeed, in all of those forms of discourse that are, or at least purport to be, about objects and states of affairs in the world independent of us, all those forms of explaining, stating, describing, ordering, requesting, promising, and so on, that are about features of the real world.
Only near the end of the first chapter did we begin to discuss how things really are in the world. At this point, we are no longer dealing with matters of philosophical analysis but actually discussing some of the results of modern science. As far as we know anything at all about how the world works, there are two propositions of modern science that are not, so to speak, up for grabs. They are not optional. It might turn out in the end that they are false, but given the overwhelming amount of evidence for them, they are not seriously in dispute among educated members of our civilization at the turn of the millennium. These are the atomic theory of matter and the evolutionary theory of biology. On the basis of these theories, we can say the following: the universe consists entirely of entities that we find it convenient, if not strictly accurate, to call “particles” in fields of force. These particles are often organized into systems. The boundaries of a system are set by its causal relations. Examples of systems are mountains, glaciers, trees, planets, galaxies, animals, and molecules. Some of those systems are carbon-based organic systems, and among these organic systems are organisms that exist today as members of species that have evolved over long periods of time. The point at which our discussion in this book enters into the story of physics, chemistry, and biology is the point at which some of those types of organic systems have evolved nervous systems, and those nervous systems have evolved what we call “minds,” human and animal minds. The notion of a mind is somewhat confused and lamentable, but as T. S. Eliot said, “I gotta use words when I talk to you.” This is a word for which we do not really have an alternative in English, though I am going to suggest some other terms that will, I hope, prove more useful than the notion of “mind.”
The primary and most essential feature of minds is consciousness. By “consciousness” I mean those states of sentience or awareness that typically begin when we wake up in the morning from a dreamless sleep and continue throughout the day until we fall asleep again. Other ways in which consciousness can cease is if we die, go into a coma, or otherwise become “unconscious.” Consciousness comes in a very large number of forms and varieties. The essential features of consciousness, in all its forms, are its inner, qualitative, and subjective nature in the special senses of these words that I explain in a moment.
But first, let’s remind ourselves of the enormous variety of our conscious experiences. Think, for example, of the differences between these experiences—the smell of a rose, the taste of wine, a pain in the lower back, a sudden memory of a fall day ten years ago, reading a book, thinking about a philosophical problem, worrying about income taxes, waking up in the middle of the night filled with aimless anxiety, feeling a sudden rage at the bad driving of other drivers on the freeway, being overwhelmed by sexual lust, having pangs of hunger at the sight of exquisitely prepared food, wishing to be somewhere else, and feeling bored while waiting in a line. All of these are forms of consciousness, and though they were chosen precisely to illustrate variety, they do not begin to exhaust the actual varieties of conscious experiences. Indeed, during all of our waking lives, as well as when dreaming during sleep, we are in one or more forms of consciousness, and the conscious states have all the variety of those waking lives.
Even with all this color and variety, however, there are three features common to all conscious states: they are inner, qualitative, and subjective in special senses of these words. Let us consider these features in order. Conscious states and processes are inner in a very ordinary spatial sense in that they go on inside my body, and specifically inside my brain. Consciousness can no more lie around separate from my brain than the liquidity of water can be separated from the water, or the solidity of the table from the table. Consciousness necessarily occurs inside an organism or some other system. Consciousness is also inner in a second sense, and that is that any one of our conscious states exists only as an element in a sequence of such states. One has conscious states such as pains and thoughts only as a part of living a conscious life, and each state has the identity it has only in relation to other such states. My thought, for example, about a ski race I ran long ago, is only that very thought because of its position in a complex network of other thoughts, experiences, and memories. My mental states are internally related to each other in the sense that in order for a mental state to be that state with that character it has to stand in certain relation to other states, just as the whole system of states has to be related to the real world. For example, if I really remember running the ski race, then there must actually have been a running of the ski race by me, and that running of the ski race by me must cause my present memory of it. Thus, the ontology—the very existence of my conscious states—involves their being part of a sequence of complex conscious states that constitutes my conscious life.
Conscious states are qualitative in the sense that for each conscious state there is a certain way that it feels, there is a certain qualitative character to it. Thomas Nagel made this point years ago by saying that for every conscious state there is something that it is like to be in that conscious state.1 There is something that it is like to drink red wine, and it is quite different from what it is like to listen to music. In that sense, there is nothing it is like to be a house or a tree, because such entities are not conscious.
Finally, and most importantly for our discussion, conscious states are subjective in the sense that they are always experienced by a human or animal subject. Conscious states, therefore, have what we might call a “first-person ontology.” That is, they exist only from the point of view of some agent or organism or animal or self that has them. Conscious states have a first-person mode of existence. Only as experienced by some agent—that is, by a “subject"—does a pain exist. Objective entities such as mountains have a third-person mode of existence. Their existence does not depend on being experienced by a subject.
One consequence of the subjectivity of conscious states is that my states of consciousness are accessible to me in a way that they are not accessible to you. I have access to my pains in a way that you do not have access to my pains, but you have access to your pains in a way that I do not have access to those pains. By access, in the preceding sentence, I do not mean simply epistemic access. It is not just that I can know my own pains better than I can know your pains. On the contrary, for some feelings, such as envy or jealousy, other people are frequently in a better position to know that the agent has the feeling than the agent who is experiencing the feeling. For many such states, we sometimes know about other people’s feelings better than we know about our own. The sense in which I have an access to my states that is different from that of others is not primarily epistemic. It is not just how I know about them, though subjectivity has epistemic consequences; rather, each of my conscious states exists only as the state it is because it is experienced by me, the subject. And it is thus part of the sequence of states that constitutes my conscious life, as we saw in our discussion of the inner character of conscious states.
It is often argued that subjectivity prevents us from having a scientific account of consciousness, that subjectivity puts consciousness beyond the reach of scientific investigation. But typically, the argument rests on a bad syllogism. By exposing the fallacy in this syllogism, I believe we can come to understand subjectivity better. Here is how the argument goes:
This argument commits a fallacy, namely, the fallacy of ambiguity over the words subjective and objective. These words have different senses, which are confused in this syllogism. In what is, perhaps, the most commonsense notion of “subjectivity,” and of the distinction between “subjective” and “objective,” a statement is considered objective if it can be known to be true or false independently of the feelings, attitudes, and prejudices of people. A statement is epistemically subjective if its truth depends essentially on the attitudes and feelings of observers. I call this sense of the words—and of this distinction between objectivity and subjectivity—"epistemic objectivity” and “epistemic subjectivity.” Thus, the statement “Rembrandt was born in 1609” is epistemically objective because we can know as a matter of fact whether it is true or false regardless of how we feel about it. The statement “Rembrandt was a better painter than Rubens” is not in that way epistemically objective because its truth is, as they say, a matter of taste or opinion. Its truth or falsity depends on the attitudes, preferences, and evaluations of observers. This is the epistemic sense of the objective-subjective distinction.
But there is a different sense of these words and the correlated distinction that I call the ontological sense. Whereas the epistemic sense applies to statements, the ontological sense refers to the status of the mode of existence of types of entities in the world. Mountains and glaciers have an objective mode of existence because their mode of existence does not depend on being experienced by a subject. But pains, tickles, and itches, as well as thoughts and feelings, have a subjective mode of existence because they exist only as experienced by some human or animal subject. The fallacy in the argument was to suppose that because states of consciousness have an ontologically subjective mode of existence, they cannot be studied by a science that is epistemically objective. But that conclusion doesn’t follow. The pain in my toe is ontologically subjective, but the statement “JRS now has a pain in his toe” is not epistemically subjective. It is a simple matter of (epistemically) objective fact, not a matter of (epistemically) subjective opinion. So the fact that consciousness has a subjective mode of existence does not prevent us from having an objective science of consciousness. Science is indeed epistemically objective in the sense that scientists try to discover truths that are independent of anyone’s feelings, attitudes, or prejudices. Such epistemic objectivity does not, however, preclude ontological subjectivity as a domain of investigation.
Consciousness has for many centuries seemed to philosophers to pose a serious problem in metaphysics. How is it possible that a world consisting entirely of material particles in fields of force can contain systems that are conscious? If you think of consciousness as some separate, mysterious kind of phenomenon, distinct from material or physical reality, then it looks like you are forced to what is traditionally called “dualism,” the idea that there are two basically different kinds of phenomena or entities in the universe. But if you try to deny dualism and deny that consciousness exists as something irreducibly subjective, then it looks like you are forced to materialism. You are forced to think that consciousness, as I have described it, and as we all in fact experience it, does not really exist. If you are a materialist, then you are forced to say that there really isn’t such a thing as consciousness with a first-person, subjective ontology. Many materialists continue to use the vocabulary of consciousness, but it is quite clear that they mean something different by it. Both of these views, dualism and materialism, are quite common in philosophy to this very day.
Dualism comes in two flavors, substance dualism and property dualism. According to substance dualism, there are two radically different kinds of entities in the universe, material objects and immaterial minds. This view goes back to ancient times, but it was most famously advocated by Rene Descartes in the seventeenth century; indeed, substance dualism is sometimes called Cartesian dualism, after him. Property dualism is the view that there are two kinds of properties of objects that are metaphysically distinct. There are physical properties, such as weighing three pounds, and mental properties, such as being in pain. All forms of dualism share the view that the two types are mutually exclusive. If it is mental, it can’t, qua mental, be physical; if it is physical, it can’t, qua physical, be mental.
Many philosophers today still adhere to some form of dualism, though it is usually property dualism rather than substance dualism. But most practicing philosophers, I think, adhere to some form of materialism. They do not believe there is such a thing as consciousness “over and above” the physical features of the physical world. Materialism comes in many different varieties, and I won’t even try to list all of them, but here are some of the most famous examples:
Behaviorism says that mind reduces to behavior and dispositions to behavior. For example, to be in pain is just to engage in pain behavior or to be disposed to engage in such behavior.
Physicalism says that mental states are just brain states. For example, to be in pain is just to have your C-fibers stimulated.
Functionalism says mental states are defined by their causal relations. According to functionalism, any state of a physical system, whether a brain or anything else, that stands in the right causal relations to input stimuli, to other functional states of the system, and to output behavior, is a mental state. For example, to be in pain is to be in a state that is caused by certain sorts of stimulation of the peripheral nerve endings and, in turn, causes certain sorts of behavior and certain sorts of other functional states.
Strong Artificial Intelligence says minds are just computer programs implemented in brains, and perhaps in other sorts of computers as well. For example, to be in pain is just to be implementing the computer program for pain.
In spite of this variety, all contemporary forms of materialism known to me share the objective of trying to get rid of mental phenomena in general and consciousness in particular, as normally understood, by reducing them to some form of the physical or material. Each of the forms of materialism I have mentioned is a “nothing but” theory: each denies, for example, that pains are inner, qualitative, subjective mental phenomena and claims, to the contrary, that they are “nothing but"—behavior, computational states, and so on.
Neither dualism, whether substance or property dualism, nor materialism in any of its many forms seems to me to have a chance of being right, and the fact that we continue to pose and try to answer these questions in the antique and obsolete vocabulary of “mental” and “physical,” “mind” and “body,” should be a tip-off that we are making some fundamental conceptual mistake in how we are formulating the questions and the answers. On the one hand, dualism in any form makes the status and existence of consciousness utterly mysterious. How, for example, are we to think of any sort of causal interaction between consciousness and the physical world? Having postulated a separate mental realm, the dualist cannot explain how it relates to the material world we all live in. On the other hand, materialism seems obviously false: it ends up denying the existence of consciousness and thus denying the existence of the phenomenon that gives rise to the question in the first place. Is there a way out? Is there an alternative between the Scylla of dualism and the Charybdis of materialism? I think there is.
I hope it is clear that this debate is a clash of default positions. I have presented each in an unflattering light, but look how attractive they can be made to seem. On the one hand, it seems obvious that we have both a mind and a body, or at least that in our lives there are both physical and mental features. On the other hand, we just seem to know that the world consists entirely of physical particles and their physical properties, including the physical properties of large organizations of particles.
We will not fully understand the persistence of the mind-body problem or the appeal of the rival positions unless we see the force behind each of the clashing default positions. Dualism seems consistent with common sense. As Descartes himself said, we all have our own conscious experiences, and we can easily see that these are different from the material world that surrounds us. We each have our inner thoughts, feelings, pains, tickles, itches, and visual perceptions. In addition, there is a world of objectively existing, three-dimensional material objects, a world of chairs, tables, trees, mountains, and waterfalls. What could be more different?
Furthermore, when we think about the relation of our conscious selves to our bodies, it just seems too horrible to think that there is nothing to our selves except our bodies. It seems too awful to think that when my body is destroyed, I will cease to exist; and even if in moments of great courage I can accept my own future nonexistence, it is much harder to accept the ultimate extinction of the people I most deeply love and admire. It seems too horrible to contemplate that such wonderful people will simply be annihilated with the inevitable death, decay, and destruction of their bodies, which, after all, are just material objects in the world like any others. Dualism, in short, not only is consistent with the most obvious interpretation of our experiences but it also satisfies a very deep urge we have for survival.
I used to think that dualism might be a special product of Western culture, but when I lectured in a symposium in Bombay, on the same platform as the Dalai Lama, I discovered to my surprise that he believed in a version of dualism. “Each of us is both a mind and a body,” he began his speech.
Materialism, on the other hand, is also overwhelmingly convincing. We now have several centuries of scientific advance, and if there is one thing we know it is that the world consists entirely of physical particles in fields of force. If we suppose that there are such things as real conscious phenomena, how are we supposed to think they fit into the world of material particles? Are we to think that souls run in and out among the molecules, or are we to think that somehow the soul is attached to the brain, stuck onto it by some metaphysical glue, and that when we die the soul becomes detached? It seems that the only way we can account for our own existence, consistent with what we know about the world from science, is to recognize that everything is material. There isn’t anything in addition to material reality—there is nothing “over and above” material reality.
This is typical of philosophical problems that seem insoluble. We are presented with two inconsistent alternatives neither of which it seems possible to abandon. But, we are told, we must choose one. The history of the subject then becomes a battle between the two sides. In the case of consciousness and the mind-body problem, we were told that we had to choose between dualism, which insists on the irreducibility of the mental, and materialism, which insists that consciousness must be reducible, and hence eliminable, in favor of some purely physical existence of the mind. As traditionally understood, both default positions have implications that seem, frankly, preposterous. That is—and this again is typical of apparently insoluble philosophical problems—we start with a position that seems commonsensical, but when we work out its implications, the position appears to have unacceptable consequences. Thus, the implication of the commonly accepted default view that each of us is both a mind and a body, when worked out in the traditional way, is that our consciousness is floating free from the physical world and is not a part of our ordinary biological lives. The default position of materialism is that the world is made up entirely of material or physical entities. The implication, when you work it out the way materialists usually do, is that consciousness, as something irreducibly mental, does not exist. Materialists, after a lot of beating around the bush, do typically end up by denying the existence of consciousness, even though most of them are too embarrassed to come right out and say: “Consciousness does not exist. No human or animal has ever been conscious.” Instead, they redefine “consciousness” so that it no longer refers to inner, qualitative, subjective mental states but rather to some third-person phenomena, phenomena that are neither inner, qualitative, nor subjective in the senses I have explained. Consciousness is reduced to the behavior of the body, to computational states of the brain, information processing, or functional states of a physical system. Daniel Dennett is typical of materialists in this regard. Does consciousness exist for Dennett? He would never deny it. And what is it? Well, it is a certain bunch of computer programs implemented in the brain.2
Such answers, I am afraid, will not do. Consciousness is an inner, subjective, first-person, qualitative phenomenon. Any account of consciousness that leaves out these features is not an account of consciousness but of something else.
I believe the correct way to solve this problem is to reject both alternatives. Both dualism and materialism rest on a series of false assumptions. The main false assumption is that if consciousness is really a subjective, qualitative phenomenon, then it cannot be part of the material, physical world. And indeed, given the way the terms have been defined since the seventeenth century, that assumption is true by definition. The way Descartes defined “mind” and “matter,” they are mutually exclusive. If something is mental, it cannot be physical; if it is physical, it cannot be mental. I am suggesting that we must abandon not only these definitions but also the traditional categories of “mind,” “consciousness,” “matter,” “mental,” “physical,” and all the rest as they are traditionally construed in our philosophical debates.
Look what happens when we try to stick to the traditional definitions. Consciousness is a biological process that occurs in the brain in the way that digestion is a biological process that occurs in the stomach and the rest of the digestive tract. So it looks like consciousness is material and we have a materialist account. But wait! Consciousness has a first-person ontology and so cannot be material, because material things and processes all have a third-person objective ontology. So it looks like consciousness is mental and we have a dualist account.
If we accept these definitions, we have a contradiction. The solution is to abandon the definitions. We now know enough biology to know that these definitions are inadequate to the facts. It is always a good idea to remind ourselves of the facts, to remind ourselves of what we actually know. We know for a fact that all of our conscious states are caused by brain processes. This proposition is not up for grabs. There is a mystery that many philosophers are impressed by—how brain processes could cause consciousness—and there is, I think, a more serious mystery, faced by neurobiologists—how brain processes do in fact cause consciousness. But one thing we have to accept before we ever get going in this discussion is that, in fact, brain processes do cause consciousness. That leaves us with the next question: What is this consciousness that they cause, and doesn’t the causal relation between consciousness and brain processes force us into dualism—a dualism of the material brain processes that act as cause and the nonmaterial subjective processes of consciousness that are the effects?
I do not think we are forced to either dualism or materialism. The point to remember is that consciousness is a biological phenomenon like any other. It is true that it has special features, most notably the feature of subjectivity, as we have seen, but that does not prevent consciousness from being a higher-level feature of the brain in the same way that digestion is a higher-level feature of the stomach, or liquidity a higher-level feature of the system of molecules that constitute our blood. In short, the way to reply to materialism is to point out that it ignores the real existence of consciousness. The way to defeat dualism is simply to refuse to accept the system of categories that makes consciousness out as something nonbiological, not a part of the natural world.
I said that we should not think of dualism as a theory exclusive to Western philosophy. Its wider appeal is illustrated by the fact that an Eastern religious figure such as the Dalai Lama also embraces it. But though it is, so to speak, “multicultural,” it is not universal. I was deeply impressed by an African friend of mine who told me that in his native African language the “mind-body problem,” as we think of it, cannot even be stated. I am now trying to revise the European conceptual categories so that the problem is no longer stateable in the way that it has traditionally been presented. Grant me that consciousness, with all its subjectivity, is caused by processes in the brain, and grant me that conscious states are themselves higher-level features of the brain. Once you have granted these two propositions, there is no metaphysical mind-body problem left. The traditional problem arises only if you accept the vocabulary with its mutually exclusive categories of mental and physical, mind and matter, spirit and flesh. Of course, consciousness is still special among biological phenomena. Consciousness has a first-person ontology and so cannot be reduced to, or eliminated in favor of, phenomena with a third-person ontology. But that is just a fact about how nature works. It is a fact of neurobiology that certain brain processes cause conscious states and processes. I am urging that we should grant the facts without accepting the metaphysical baggage that traditionally goes along with the facts.
When I say that the brain is a biological organ and consciousness a biological process, I do not, of course, say or imply that it would be impossible to produce an artificial brain out of nonbiological materials that could also cause and sustain consciousness. The heart is also a biological organ, and the pumping of blood a biological process, but it is possible to build an artificial heart that pumps blood. There is no reason, in principle, why we could not similarly make an artificial brain that causes consciousness. The point that needs to be emphasized is that any such artificial brain would have to duplicate the actual causes of human and animal brains to produce inner, qualitative, subjective states of consciousness. Just producing similar output behavior would not by itself be enough.
We can summarize these points in the following propositions.
But that is it. That is our account of the metaphysical relations between consciousness and the brain. Nowhere do we even raise the questions of dualism and materialism. They have simply become obsolete categories.
We have thus “naturalized” consciousness, and indeed, my label for this view is “biological naturalism": “naturalism” because, on this view, the mind is part of nature, and “biological” because the mode of explanation of the existence of mental phenomena is biological—as opposed to, for example, computational, behavioral, social, or linguistic.
This method, I believe, is one of the ways to make progress in philosophy. When confronted with an intractable question such as is presented by a clash of convincing default positions, don’t accept the question lying down. Get up and go behind the question to see what assumptions lie behind the alternatives the question presents. In this case, we did not answer the question in terms of the alternatives presented to us but we overcame the question. The question was, is dualism or materialism the correct analysis of the mental? The answer is: as traditionally conceived, neither; as revised, both. Hence it is best to reject the vocabulary of “dualism” and “materialism” altogether and start over. The answer is then given by propositions 1–5. The view can be summarized even more succinctly by saying: consciousness is caused by brain processes and is a higher-level feature of the brain system.
The way we proceeded was to start by reminding ourselves of what we know about how the world works. In this case, we know that consciousness consists in states and processes that are ontologically subjective, are caused by processes in the brain, and are realized in the brain. We then saw that the picture that emerged from our knowledge of the facts was inconsistent with both of the traditional alternatives presented to us, dualism and materialism. So our next step was to ask: What are both theories assuming that makes the initial question seem insoluble? And the answer is that they are assuming, as Descartes did, that the categories of mind and body, of matter and consciousness, are mutually exclusive. Our solution, then, was to get rid of those categories. In so doing, we found we could consistently accept all of the facts that we knew independently of our philosophical commitments.
I have said that the subjectivity of consciousness makes it irreducible to third-person phenomena, according to the standard models of scientific reduction. But why exactly? The problem can be put as follows: if, as I have been insisting, consciousness is an ordinary biological phenomenon like mitosis, meiosis, or digestion, then we ought to be able to say exactly how consciousness reduces to micro-phenomena in a way that mitosis or digestion do. Thus, for example, in the case of digestion, once you have told the entire story about the enzymes, the renin, the breakdown of the carbohydrates, and so on, there is nothing more to say. There isn’t any further property of digestion in addition to that. And, of course, those processes have a farther description in the behavior of even more micro-elements, such as quarks and muons, until finally we get to the most fundamental quantum phenomena. But in consciousness, the situation seems to be different, because once we have explained the causal basis of consciousness in terms of the firing of neurons in the thalamus and the various cortical layers, or, for that matter, in terms of quarks or muons, it seems we still have a phenomenon left over. In the case of consciousness, we have an irreducible subjective element left after we have given a complete causal account of the neurobiological basis. What is going on? Doesn’t this force us to property dualism?
In order to answer this question, I have to say a bit more about scientific reduction. There are very many different kinds of scientific reduction, and the notion is not at all clear. For present purposes, however, we need to distinguish between two kinds of reduction that I call “eliminative” and“non-eliminative” reduction. Eliminative reductions get rid of a phenomenon by showing that it really doesn’t exist, that it was just an illusion. For example, when we explain the appearance of sunrises and sunsets, there is a sense in which we eliminate sunrises and sunsets because we show they are only illusions. The sun does not really set over the mountains—rather, the rotation of the earth on its axis makes it appear that the sun sets.
This is different from the non-eliminative reduction of features such as liquidity and solidity. Solidity can be entirely explained causally in terms of the vibratory motions of molecules in lattice structures. Once the molecules are moving in this way, then objects are impenetrable by other objects. They support other objects, and so forth. Solidity is causally explainable in terms of the behavior of micro-elements, and for that reason we redefine solidity in terms of its causal basis. The reduction of solidity to the movement of molecules is a non-eliminative causal reduction. The table does not just appear to be solid, it is solid.
Now, and here is the point, we cannot make either of these moves with consciousness. Why not? We cannot perform eliminative reduction on consciousness because the pattern of eliminative reductions is to show that the phenomenon reduced is just an illusion. But where consciousness is concerned, the existence of the “illusion” is the reality itself. That is to say, if it seems to me that I am conscious, then I am. There isn’t anything more to consciousness than a sequence of just such “seemings.” In this respect, consciousness differs from sunsets because I may have the illusion of the sun setting behind the mountains when it does not really do so. But I cannot in that way have the illusion of consciousness if I am not conscious. The “illusion” of consciousness is identical with consciousness.
But why can’t we perform a reduction of consciousness to its micro-physical causal basis as we can perform a reduction of, for example, solidity to its micro-physical basis? Well, I believe we could if we were willing to leave out subjectivity and just talk about its causes. We might, for example, become so medically sophisticated that we could look at a person’s brain with our brain-o-scope and see that he was suffering a pain in his elbow, just because we could see that the appropriate neuron firings were going on. For scientific purposes, we might even define a pain in the elbow as a sequence of certain sorts of neuron firings occurring in such and such a place in the brain. But we leave something out in this case, something essential to our concept of consciousness. What we leave out is subjectivity. Consciousness has a first-person ontology, and we cannot for that reason perform a reduction on consciousness that we can on third-person phenomena, without leaving out its essential character. Notice that when we reduce solidity to molecule motion, we leave out the subjective experiences of people who encounter solid objects. We simply carve off the subjective experiences, because they are not essential to our concept of solidity. But we cannot carve off the subjective experiences of consciousness, because the whole point of having the concept of consciousness in the first place is to have a name for the subjective first-person phenomena. Although consciousness is a biological phenomenon like any other, its subjective, first-person ontology makes it impossible to reduce it to objective third-person phenomena in the way that we can reduce third-person phenomena such as digestion or solidity.
Suppose for the sake of argument that I am right so far: consciousness is indeed caused by lower-level biological processes in the brain and is itself a higher-level feature of the brain system. Traditional philosophers, still in the grip of the dualistic categories, will immediately pose the following objection: on this view, consciousness must be epiphenomenal. What they mean by that is that consciousness, though caused by brain processes, cannot itself cause anything. It is just a kind of vaporous residue cast off by the brain, but is unable to do anything on its own. Indeed—as the objector presses the argument more aggressively—it must follow from the account so far that consciousness is a kind of residue that doesn’t function causally in producing anything. So, for example, if you raise your arm, you will think that your conscious decision caused your arm to go up, but in fact we all know that there is a detailed causal story to be told at the level of neurons in the motor cortex, neurotransmitters, especially acetylcholene, axon endplates, muscle fibers, and all the rest of the neurophysiology that is quite sufficient to give a complete causal account of the movement of your arm independent of any reference to consciousness. So, it seems that any realist account of consciousness, as I have been proposing, must render it epiphenomenal. It must render consciousness utterly useless and irrelevant to what happens in the world.
How shall we reply to epiphenomenalism? One consideration occurs immediately: it would be miraculous, unlike anything that ever occurred in biological history, if something in biology as elaborate, rich, and structured as human and animal consciousness made no causal difference to the real world. From what we know about evolution, it is unlikely that epiphenomenalism could be right. This is not a decisive objection to epiphenomenalism, but it ought at least to make us wrinkle our noses at the thought of epiphenomenalism. What, then, is the answer? Once again, let’s go behind the question and ask: What is being presupposed by the challenge of epiphenomenalism?
The standard model of causation, the earliest experience of causes that the child gets, and the most primitive concept of causation we have, is the notion of one object exerting a physical pressure on another. Piaget’s researches on the early development of children show that the child’s most primitive concept of causation is a “push-pull” concept.3 One object pushes against another, and the child pushes and pulls against objects. This is how the child acquires his or her most basic concept of causation. As the child comes to understand more about how the world works—and more important, as we come to understand scientifically how the world works—we get a much more expanded and richer conception of causal relations. We can then see that causation is in general a matter of one thing making something else happen, and thus we can talk not only about the causes of buildings collapsing but about the causes of wars and economic depressions, the causes of mental illness and changes in popular culture. Causation, in short, is not just a matter of pushing and pulling, it is a matter of something being responsible for something else happening.
Let us think for a moment about how consciousness works in real life to make things happen. I consciously raise my arm, and my conscious effort causes my arm to go up. My conscious effort actually produces a change in the position of my arm. Prereflectively we do not doubt that this happens in real life. When we begin to have skeptical philosophical doubts about how it could happen, about how the experienced causal relation can be made consistent with our “scientific worldview,” I believe that we are combining our residual dualism with an extremely naive conception of causal relations. If we start with push-pull, billiard-ball causation, it will seem puzzling that mental states can cause physical changes. It will seem even more puzzling if we think with the dualists that the “mental” is not part of the “physical” world.
But suppose we reject both of these assumptions. Suppose we start with what we independently know. Suppose we start with the fact that the mind affects the body and the body affects the mind, and go from there. That is, let us assume at the start what we all know from our own experiences—that there are causal relations between consciousness and other physical events. For example, when I consciously intend to raise my arm, my conscious state causes my arm to go up; when I bump into a solid object, the impact of the object causes me to feel a sensation of pain. Let us start, at least provisionally, with an acceptance of these facts and then redraw the conceptual map so that it accurately reflects them.
This redrawing of the conceptual map to reflect the facts is typical of the growth of philosophical and scientific understanding. An early objection to Newtonian mechanics was that gravitation as a causal force seemed to imply “action at a distance.” To avoid the absurdity of action at a distance, we seemed to be forced to think of gravitation as a matter of invisible strings tying planetary bodies together. Today nobody makes this sort of objection. We have a much richer conception of causation, which includes, among other things, fields of force. We no longer suppose that in order for one planet to act causally on another there must be a physical object connecting the two, so that they can push or pull one another.
But once again, the objector will ask, “How is it possible that the mind can affect the body?” That is, the objector will complain that it is not enough for me to keep roundly insisting that intuitively we feel that epiphenomenalism is false. Can there be any grounds for this feeling? What is the conceptual map supposed to look like when we have redrawn it in such a way as to make mind-body causation possible?
Our first step was to remove the assumption that all causation is a case of something pushing or pulling something else. Not all causation is billiard-ball causation. The second and final step is to remind ourselves of how causation works in physical systems anyway. If you think of the behavior of your car engine, for example, you will see that there are different causally real levels of description. At one level, we talk about the action of the piston, the cylinders, the spark plugs, and the explosion in the cylinder. At a lower level, we can talk about the passage of electrons across the electrodes, the oxidization of hydrocarbons, the molecular structure of the metal alloys, and the formation of new compounds such as CO and CO2. These are two quite distinct levels of description of the behavior of an engine, but there is nothing inconsistent between these two descriptions, and there is no reason to regard the higher-level description as epiphenomenal or causally unreal. Of course, everything in nature has to bottom out at the most basic level—the level of quarks and muons and subatomic particles. The fact that any given causal level is grounded in more fundamental levels until finally we reach the basic level of the micro-particles does not show that the higher level is not causally real. In short, the argument for the epiphenomenalism of the mental is no stronger than for the epiphenomenalism of pistons and cylinders. The fact that you can give a causal account at the lower level does not imply that the higher levels are not real. That is, our provisional acceptance of the causal efficacy of consciousness is not threatened by pointing out that any explanation at the level of consciousness is grounded in more fundamental physical phenomena, because it is true of any physical system whatever that causal explanations at the higher levels are grounded in more fundamental micro-physical explanations at the lower levels. It does not prove that the solidity of the piston is epiphenomenal to point out that solidity is explainable in terms of the molecular behavior of the alloys; similarly, it does not prove that intentions are epiphenomenal to point out that intentions are explainable in terms of neurons, synapses, and neurotransmitters.
To summarize our reply to epiphenomenalism, we can say that three mistakes underlie the epiphenomenalist argument.
I believe all three of these assumptions are unjustified, indeed false, and once their falsity has been pointed out, I believe there is no ground for saying that consciousness is epiphenomenal.
I want to make my position absolutely clear here. I am not saying that it is a matter of logic that epiphenomenalism is false. As far as logical possibility is concerned, it might turn out that mental states are totally epiphenomenal and thus do not play any causal role. Such a possibility is logically conceivable, but as far as we know, it is just a plain fact about how the world works that our conscious mental states function causally in the production of our behavior. The world might have turned out differently, but this is how it turned out in fact. I have tried to remove the grounds for doubting this fact. I have tried to remove the grounds for thinking that consciousness must be epiphenomenal, but I have not proved that epiphenomenalism is logically absurd. I believe it is false, but the form of falsity in question is empirical falsity, not logical absurdity. If epiphenomenalism did turn out to be true, it would be the greatest scientific revolution in the history of the world and would alter our whole way of thinking about reality. My aim here was to remove the reasons for thinking that epiphenomenalism must be true.
This raises the question, what is the evolutionary function of consciousness? What is its evolutionary value? What does it do? What good is it for survival?
This question is sometimes asked in a polemical, rhetorical tone, as if to suggest that maybe consciousness doesn’t matter, that maybe it is just going along for a free ride, and that we could just as well have evolved without it. This is a very strange suggestion to make, because much of what we do that is essential to the survival of our species requires consciousness: you cannot eat, copulate, raise your young, hunt for food, raise crops, speak a language, organize social groups, or heal the sick if you are in a coma. The polemical suggestion is that somehow or other we could imagine beings like ourselves having evolved ways of doing these things without consciousness.
Well, we can imagine any science fiction fantasy we like. But in the real world, the way that humans and higher animals typically cope is by way of conscious activities. We can imagine plants producing food by some method other than photosynthesis, but this does not show that photosynthesis has no function in evolution. In the real world, plants need photosynthesis, and humans need consciousness, in order to survive.
There is something extremely puzzling about the claim that consciousness plays no evolutionary role, because it is obvious that consciousness plays a large number of such roles. The skeptics on this issue I believe are still tacitly assuming a dualism of mind and body when they make the skeptical challenge. Here is how. The normal way we have of inquiring into the evolutionary role of some phenotypical trait is to imagine the absence of that trait, while holding the rest of nature constant, and then see what happens. When you imagine that plants could not perform photosynthesis or that birds could not fly, holding the rest of nature constant, you can see the evolutionary advantage of these traits. Now try it with consciousness. Imagine that we all fall into a coma and lie around prostrate and helpless. You see that we would soon become extinct, but that is not the way the skeptic imagines it. He imagines that our behavior remains the same, only minus consciousness. But that is precisely not holding the rest of nature constant, because in real life much of the behavior that enables us to survive is conscious behavior. In real life you cannot subtract the consciousness and keep the behavior. To suppose you can is to suppose that consciousness is not an ordinary physical part of the physical world. That is, it is to suppose a dualistic account of consciousness. Skepticism about the evolutionary role of consciousness thus presupposes that consciousness is not already an ordinary part of the physical biological world that we all live in.
I have been talking as if consciousness functioned causally, so to speak, just like that. The way an explosion knocks over a building, for example. But typically a conscious state such as an intention or a desire functions by representing the sort of event that it causes. For example, I want to drink water, so I drink water. Here the effect, drinking water, is consciously represented by the cause, the desire to drink water. This sort of mental causation I call “intentional causation,” for reasons that emerge in chapter 4. At this point, I just want to remark on the amazing property that conscious beings have to represent objects and states of affairs in the world and to act on the basis of those representations. It is a general feature of most, though not all, conscious phenomena that they represent objects, events, and states of affairs in the world. Indeed, the most important feature of consciousness for the purpose of this discussion is that there is an essential connection between consciousness and the capacity that we human beings have to represent objects and states of affairs in the world to ourselves. This is a feature possessed by beliefs and desires, hopes and fears, love and hate, pride and shame, as well as perception and intention. It is a feature that has a technical name in philosophy: “intentionality.” Intentionality is that feature of the mind by which mental states are directed at, or are about or of, or refer to, or aim at, states of affairs in the world. It is a peculiar feature in that the object need not actually exist in order to be represented by our intentional state. Thus, the child can believe that Santa Claus will come on Christmas Eve, even though Santa Claus doesn’t exist.
Not all conscious states are intentional, and not all intentional states are conscious. Thus, for example, there are conscious feelings of anxiety or elation for which there is no answer to the question, “What are you anxious about or what are you elated about?” These are non-intentional forms of consciousness. And of course, there are many forms of intentionality that are not conscious. I have beliefs and desires, hopes and fears, even when I am sound asleep. It is true to say of me that I believe that Bill Clinton is president of the United State even at times when I am totally unconscious. But that belief then exists in an unconscious form. It still has its intentionality, but it is no longer conscious.
Nonetheless, though not all conscious states are intentional, and not all intentional states are conscious, there is an essential connection: we only understand intentionality in terms of consciousness. There are many intentional states that are not conscious, but they are the sort of thing that could potentially be conscious.
In the next two chapters, we explore the structure of consciousness and the structure of intentionality.