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Consciousness & the Philosophers

The Conscious Mind: In Search of a Fundamental Theory

by David J. Chalmers
Oxford University Press, 414 pp., $29.95


Traditionally in the philosophy of mind there is supposed to be a basic distinction between dualists, who think there are two fundamentally different kinds of phenomena in the world, minds and bodies, and monists, who think that the world is made of only one kind of stuff. Dualists divide into “substance dualists,” who think that “mind” and “body” name two kinds of substances, and “property dualists,” who think “mental” and “physical” name different kinds of properties or features in a way that enables the same substance—a human being, for example—to have both kinds of properties at once. Monists in turn divide into idealists, who think everything is ultimately mental, and materialists, who think everything is ultimately physical or material.

I suppose most people in our civilization accept some kind of dualism. They think they have both a mind and a body, or a soul and a body. But that is emphatically not the current view among the professionals in philosophy, psychology, artificial intelligence, neurobiology, and cognitive science. Most of the people who work in these fields accept some version of materialism, because they believe that it is the only philosophy consistent with our contemporary scientific world view. There are a few property dualists, such as Thomas Nagel and Colin McGinn, but the only substance dualists I know of are those who have a religious commitment to the existence of a soul, such as Sir John Eccles, a prominent British neurophysiologist.

But materialists have a problem: once you have described all the material facts in the world, you still seem to have a lot of mental phenomena left over. Once you have described the facts about my body and my brain, for example, you still seem to have a lot of facts left over about my beliefs, desires, pains, etc. Materialists typically think they have to get rid of these mental facts by reducing them to material phenomena or by showing that they don’t really exist at all. The history of the philosophy of mind over the past one hundred years has been in large part an attempt to get rid of the mental by showing that no mental phenomena exist over and above physical phenomena.

It is a fascinating study to try to trace these efforts, because typically their motives are hidden. The materialist philosopher purports to offer an analysis of the mental, but his or her hidden agenda is to get rid of the mental. The aim is to describe the world in materialist terms without saying anything about the mind that does not sound obviously false. That is not an easy thing to do. It sounds too implausible to say right out that pains and beliefs and desires don’t exist, though some philosophers have said that. The more common materialist move is to say, yes, mental states really do exist, but they are not something in addition to physical phenomena; rather they can be reduced to, and are forms of, physical states.

The first of the great twentieth-century efforts to offer a materialist reduction of the mind was behaviorism—the view, presented by Gilbert Ryle and Carl Gustav Hempel, that mental states are just patterns of behavior and dispositions to behavior, when “behavior” just means bodily movements which have no accompanying mental component. Speech behavior, for example, according to the behaviorists’ conception, is just a matter of noises coming out of one’s mouth. Behaviorism sounds obviously false because, for example, everyone knows that a feeling of pain is one thing and the behavior associated with pain is another. As C.K. Ogden and I.A. Richards once remarked, to believe in behaviorism you have to be “affecting general anÌ?sthesia.”1

Another difficulty with behaviorism is that it is unable to account for our intuition that mental states cause behavior. For example, according to the behaviorist analysis, my belief that it is raining consists of patterns of behavior and dispositions to behavior. That I have such a belief consists in such facts as, for example, the fact that I wear a raincoat and carry an umbrella when I go out. (And remember, these behaviors are just bodily movements. We are not to think of them as having some mental component.) But our natural inclination is to say that the belief causes the behavior, not that the belief just is the behavior.

Furthermore, it seems the behaviorist analysis as it stands cannot be right as a reduction of the mental to behavior, because it is circular. To analyze some mental states you have to presuppose other mental states. For example, my belief that it is raining will be manifested in carrying an umbrella only if I also have a desire not to get wet. My desire not to get wet will manifest itself in this behavior only if I have the belief that the umbrella will keep me dry. So there are at least two difficulties with behaviorism besides the obvious one that it seems implausible. The first is that it cannot account for the causal relations between mind and behavior, and the second is that the relation between a mental state and behavior cannot be analyzed without mentioning other mental states. To analyze beliefs you have to have desires, and, conversely, to analyze desires you have to have beliefs.

In light of these difficulties, the next great move of the materialists was to say that mental states are identical with states of the brain. This theory, put forth by J.J.C. Smart and others, is called “physicalism” or “the identity theory,” and it comes in different versions. But it too has difficulties. One difficulty is that we need to be able to explain what it is about a state of a brain that makes it a mental state as opposed to other states of the brain that are not mental states. Furthermore, it seems too restrictive to say that only brains can have mental states. Why couldn’t we build a machine, for example a computer, that also had mental states but did not have anything like the physical states that exist in brains? Why couldn’t there be organisms from other planets or other solar systems who had minds but had a different chemistry from ours?

The difficulties of behaviorism and of the identity theory led to a new theory, called “functionalism,” which is supposed to combine the best features of physicalism and behaviorism, while avoiding many of their difficulties. Functionalism is the most widely held theory of the relation between mind and body among philosophers today. According to its proponents, such as Hilary Putnam and David Lewis, mental states are physical states all right, but they are defined as “mental” not because of their physical constitution but because of their causal relations. We all know of concepts that can be defined functionally, in terms of their causal relations, and we should understand mental concepts by analogy with such concepts.

Think of clocks and carburetors, for example. All clocks and carburetors are physical objects, but they can be made out of different kinds of materials. Something is a clock or a carburetor in virtue of what it does, of what its causal relations are, and not in virtue of the materials it is composed of. Any material will do, provided it does the job (or “functions”) so as to produce a specific result, in these cases to tell the time or mix air and fuel. The situation is essentially the same, the functionalists argue, with mental states. All beliefs and desires are physical states of physical “systems,” but the systems can be made out of different kinds of materials. Something is a belief or a desire in virtue of what it does, what its causal relations are, and not in virtue of the materials that its system is composed of. So brains, computers, extraterrestrials, and no doubt other “systems” can have minds provided they have states with the right causal relations.

Here is how a typical functionalist analysis goes. Suppose I believe that it is raining. That belief will be a state of my brain, but a computer or some other system might have the same belief although it has a completely different physical/chemical composition. So what fact about my brain state makes it that belief? The functionalist answer is that a state of a system—human, computer, or otherwise—is a belief that it is raining if the state has the right causal relations. For example, my belief is a state of my brain caused by my looking out the window when rain is falling from the sky, and this state together with my desire not to get wet (another functional state of my brain) causes a certain sort of output behavior, such as my carrying an umbrella. A belief, then, is any physical state of any physical system which has certain sorts of physical causes, and together with certain sorts of other functional states such as desires, has certain sorts of physical effects.

And remember, none of these causes and effects is to be thought of as having any mental component. They are just physical sequences. The functionalist is emphatically not saying that a belief is an irreducible mental state which in addition has these causal relations, but rather that being a belief consists entirely in having these causal relations. A belief can consist of a bunch of neuron firings, voltage levels in a computer, green slime in a Martian, or anything else, provided that it is part of the right sort of pattern of cause-and-effect relations. A belief, as such, is just a something, an X, that is part of a pattern of causal relations, and it is defined as a belief because of its position in the pattern of causal relations. This pattern is called the “functional organization” of a system, and for a system to have a belief is just for it to have the right functional organization. A functional organization of a system takes a physical input, processes it through a sequence of internal cause-and-effect relations within the system, and produces a physical output.

The word “functionalism” may be confusing because it means many different things in many different disciplines; but in the philosophy of mind, as we have seen, it has a fairly precise meaning. Functionalism, for contemporary philosophers, is the view that mental states are functional states and functional states are physical states; but they are physical states defined as functional states in virtue of their causal relations.

Nobody ever became a functionalist by reflecting on his or her most deeply felt beliefs and desires, much less their hopes, fears, loves, hates, pains, and anxieties. The theory is, in my view, utterly implausible, but to understand its appeal you have to see it in historical context. Dualism seems unscientific and therefore unacceptable; behaviorism and physicalism in their traditional versions have failed. To its adherents, functionalism seems to combine the best features of each. If you are a materialist, functionalism may seem the only available alternative, and this helps explain why it is the the most widely held theory in the philosophy of mind today. In its version linked to the use of computers, it has also become the dominant theory in the new discipline of cognitive science.

  1. 1

    C.K. Ogden and I.A. Richards, The Meaning of Meaning (Harcourt Brace, 1923), p. 23.

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