The Mind-Body Problem IB
12
The Mind-Body Problem IB
Physicalist Alternatives to Property Dualism or Mere-Property Dualism
The growth in influence and the popularization of physical science has made the problem [of the mind] more urgent. The idea that science captures everything, except the centre of everyone’s universe, his own consciousness, makes a laughing-stock of its claim to present a plausible world view. . . . If science cannot encompass the subjective then subjectivity becomes a door through which mystical, irrational and religious notions can enter and reassert themselves against the modern metaphysic of scientific realism.
Howard Robinson, Matter and Sense
Seen from the perspective of the last fifty years, the philosophy of mind, as well as cognitive science and certain branches of psychology, present a curious spectacle. The most striking feature is how much of mainstream philosophy of mind of the past fifty years seems obviously false.
John Searle, The Rediscovery of the Mind
1—Introduction
In the last chapter, we began our investigation of the mind-body problem by examining the position known as mere-property dualism and property dualism simpliciter. Mere-property dualism holds that while consciousness and mental properties/states are immaterial and not physical, the possessor of consciousness is a physical entity—for example, the brain or a subregion of the brain. By contrast, we defined “property dualism” as the view that both consciousness and its possessor (e.g., a mind, soul, self) are immaterial and not physical. A substance dualist accepts property dualism because he takes consciousness to be immaterial. But he does not accept mere-property dualism because he rejects the idea that the possessor of consciousness is a physical entity of some kind.
In this chapter, for two reasons, we will look at the major rivals to mere-property dualism—key versions of physicalism regarding consciousness and mental properties/states. First, we want to keep the focus on physicalist versions of consciousness and not on the self. Second, everyone who rejects the immateriality of consciousness also rejects an immaterial soul or mind. The battle for them is not about the nature of the possessor of consciousness. Allegedly, that battle has been won by physicalists. We will see in the next two chapters that this claim is far from the truth. Rather, physicalists think that the battle now is about the nature of consciousness and mental properties/states, that is, about mere-property dualism. So our focus will be on physicalist alternatives to mere-property dualism.
At the beginning of chapter eleven we defined physicalism as the view that all entities whatsoever are merely physical entities. Here a “physical entity” means one that can be completely described using the language of the hard sciences, especially chemistry and physics. In the last section of this chapter, we will look at why this understanding of physical is the most reasonable one for modern physicalists to take. Until then, this sense of the term will be utilized without further comment.
Applied to the mind-body problem, a physicalist believes that a human being is merely a physical entity. In this chapter, we will focus on consciousness and mental properties/states. Not all physicalists are agreed as to how physicalism should analyze mental properties/states. Figure 12.1 depicts the major contemporary forms of physicalism.
Figure 12.1. Varieties of reductive and nonreductive physicalism
The figure shows two main physicalist strategies with different varieties of each: reductive and nonreductive physicalism. (The last section of chapter fifteen discusses the nature of reductionism, and it would be a good idea to read that section before proceeding.) In the context of the mind-body problem, reductive and nonreductive physicalism mean something fairly specific. To understand these approaches to philosophy of mind, consider any type of mental state—a pain type state, being an awareness of red, thinking that 2 + 2 = 4. Each of these mental states is a repeatable type of state. One person can be in that very same type of state on different occasions, and many people can be in the same type of state at the same time. Now according to reductive physicalism, it is possible to provide general, reductive, nonmentalistic necessary and sufficient conditions for any mental type of state. For example, it would be possible to state a set of necessary and sufficient conditions in physical terms for any and all instances of being in a painful type of state. Philosophical behaviorism and type-type identity theory are different ways of spelling out what these conditions are.
By contrast, nonreductive physicalism does not believe that such a general set of necessary and sufficient conditions exist or are necessary in order to provide physicalist treatments of mental entities. Nonreductive physicalists agree that everything about a human being—all of his or her parts, properties, and states—is merely physical. But they do not believe that it is possible or necessary to state general conditions for ascribing a type of “mental state” to a human being. Thus nonreductive physicalists would not offer general conditions in physical terms for ascribing a pain type state to a human being. Token-token identity theory, functionalism, and eliminative materialism are the three main versions of nonreductive physicalism. We will return to nonreductive physicalism at the end of section two of this chapter.
Functionalism was just characterized as a form of nonreductive physicalism. But this claim is not entirely accurate, and philosophers disagree about whether functionalism is a version of nonreductive physicalism. The disagreement turns on different understandings of reduction. As we have used the term, reduction requires that one provide a set of necessary and sufficient conditions for every mental type (e.g., being a pain) in terms of a uniform set of physical conditions. As we shall see later, this has proved impossible because of the problem of multiple realization. Roughly, this problem turns on the fact that creatures with radically different brain and physical types of states—humans, Vulcans, dogs, turtles—can all be in the same type of mental state, say, being in pain. Thus there is no uniform set of necessary and sufficient physical conditions to which a pain type state could be reduced.
However, there is a different sort of reduction to which physicalist versions of functionalism subscribe—functional reduction. This reduction is accomplished in two steps. Step one: Functionalize the mental property. For example, the mental property of being in pain is identified with a property of having some physical property or other that plays the right role in the organism—for example, by being that physical property that is caused by pin pricks, toothaches, and so on—and which causes the organism to grimace and desire relief. Thus the mental property is reduced to the role it plays in the organism. Step two: Identify the property that plays the correct role mentioned in step 1 with a physical property. Step two requires that the only properties that realize functional roles are physical properties. This is similar to requiring that only some sort of physical hardware can be the realizer of functional roles specified in computer software. In this way, the functionalist requires that each time a human, Vulcan, dog, or turtle is in pain, that particular pain event must be taken as identical to a physical event in the brain and nervous system. Thus pain is reduced to/identified with some physical event or other, even though it remains impossible to state necessary and sufficient conditions for the type of brain event to which the type of mental state is reduced. Moreover, what makes the individual physical event a pain event is not the physical event’s intrinsic features. Rather, it is a pain event because it plays the right role in the organism. The mental type—for example, being painful—is a functional type. The mental token is a realizer of the type. Just as being a quarterback is not a property Peyton Manning has (he does have, for example, the property of such and such height), but rather, a role he plays or realized, and just as being a dollar is a role a certain piece of paper plays or realizes, in the same way, being a pain is a function role that a specific C fiber firing event realizes or plays.
Several reasons have been offered for physicalism regarding consciousness. Some of these are philosophical in nature. In fact, chapter eleven included two of them: the problem of interaction in a dualist view of a human being and the application of Ockham’s razor to the mind-body problem to support the claim that physicalism regarding consciousness is the preferred, simpler view. However, it is safe to say that the primary, most important set of arguments for this sort of physicalism in the current debate derives from science. John Searle, one of the leading philosophers of mind in the twentieth century, has made the following observation:
Acceptance of the current [physicalist] views is motivated not so much by an independent conviction of their truth as by a terror of what are apparently the only alternatives. That is, the choice we are tacitly presented with is between a “scientific” approach, as represented by one or another of the current versions of “materialism,” and an “unscientific” approach, as represented by Cartesianism or some other traditional religious conception of the mind.
In other words, the main intellectual drive that underlies physicalism regarding consciousness is not primarily philosophical arguments against dualism and in favor of physicalism, but what are taken to be the implications of a scientific, naturalistic worldview. Given that this is the case, for many physicalists, the main place that philosophy enters into the picture is in stating and defending plausible versions of physicalism regarding consciousness. With this in mind, our primary concern in this chapter will be to state and evaluate these different versions of physicalism regarding mental properties/states. This will be done in the section to follow. The chapter will conclude with a survey of some of the main arguments for physicalism regarding consciousness and some final remarks about the primary intellectual impetus behind it. In the next two chapters, we will look at issues involved in and alternatives to physicalism regarding the individual thing that has consciousness. For convenience’s sake, we will hereafter refer to physicalism regarding consciousness merely as physicalism.
2—Different Forms of Physicalism Regarding Consciousness
2.1 Philosophical Behaviorism
Behaviorism is a term usually associated with the psychologists J. B. Watson and B. F. Skinner. Currently, there are two main forms of behaviorism: methodological behaviorism and philosophical behaviorism. Methodological behaviorism is the view that in doing psychology from an empirical standpoint, one should describe, report, and explain mental states in terms of publicly observable behaviors and not in terms of private, first-person, inner conscious states. As a research strategy in psychology, methodological behaviorism implies that psychologists should limit their focus to the stimulus inputs and behavioral outputs of organisms and make no reference to introspective private mental states. Methodological behaviorism makes no commitment either way about the existence of the mental.
Philosophical behaviorism does make such a commitment: mental states are identified with overt bodily movements or tendencies to certain movements, given certain stimulus inputs. Actually, philosophical behaviorism places greater emphasis on the nature of mental terms than on the corresponding mental states themselves. Mental terms are given operational definitions (definitions of something solely in terms of what can be empirically tested or measured by certain tests or operations) such that mental terms mean public body movements or dispositions to such movement. On this view, when we say that salt is soluble, we do not attribute some occult, unobservable entity, solubility, to salt. Rather, we simply mean that if salt were put in water it would dissolve, and this statement refers only to publicly observable behaviors of salt. Similarly, to say that Jones is in pain is simply to say that, given certain inputs (e.g., being stuck with a pin), Jones has the tendency to wince and shout “Ouch!” To say that Jones wants to go to Europe is to say merely that Jones is disposed to browse brochures about Europe, to talk about European cathedrals, to google European airfares, and so on.
It is important to keep in mind that philosophical behaviorism has to focus on bodily movements and not bodily behaviors. Why? Consider a question Wittgenstein asked years ago: What is the difference between my arm going up and me raising my arm? The answer is that the former may be just a bodily movement, perhaps an unconscious response to some physical stimulus. But the latter is an intentional action, say, voting, that is done for a purpose. Body movements are purely physical: moving one’s hands, typing on a keyboard, and so on. But behaviors like writing a thank-you note or voting by raising your hand are not purely physical. In fact, what gives them their identity is their mental nature—the intent or purpose for the movement. Thus, to be a behavior, something must already involve an inner mental state. So philosophical behaviorists must limit themselves to bodily movements (or to internal physiological changes like an increase in heart rate or blood pressure).
Today, philosophical behaviorism has fallen on hard times because of the strength of the objections that have been raised against it. First, a mental state like being in pain cannot be identical to certain bodily movements or tendencies to move because one can be in pain without wincing, shouting, or engaging in any bodily movement, and one can exemplify such movement and fake being in pain even though such a mental state is not present. Since you can have pain without pain movement or tendencies to move and vice versa, the two cannot be identical. Thus the term pain cannot be defined in terms of body movements.
A closely related objection is this. By identifying pain, for example, with pain movements, philosophical behaviorists leave out the fact that pain is what causes such movement and thus cannot be identical to that movement. Third, pain is essentially characterized by a certain type of hurtful feeling that can be directly known by acquaintance with our own inner, private, first-person subjective states of sentience, but bodily movements do not have this feature, so they cannot be the same thing. In short, pains hurt, but pain movement doesn’t.
Fourth, definitions of mental states in terms of a set of conditionals become unruly and indefinitely long such that they could never be learned. For example, according to philosophical behaviorism “Jones wants to go to Europe” means that “If Jones gets travel brochures, he will get European ones, if Jones gets the money, he will buy an airplane ticket to Europe and not a new horse, and so on.” It should be obvious that there is a potentially infinite set of further conditionals that could be added to this list.
Moreover, the conditionals that make up the behaviorist definition make sense only if we fill them out by adding terms that make reference to inner mental states. For example, Jones will get a travel brochure only if he believes that such a brochure will inform him about Europe. He will buy a ticket and not a horse only if he thinks that he cannot buy both and he desires to travel more than to have a horse. Thus behaviorist definitions of mental terms are circular since, in order to be complete, they must implicitly utilize other mental terms. Thus, strictly speaking, philosophical behaviorism is not about intentional behavior at all—for example, writing an invitation, greeting someone at work, making a promise. As noted above, all of these get their identity from the mental intention of the act. No, philosophical behaviorism must cash out mental terms or states with respect to (1) overt body movements (e.g., hand movements involving scribbling on a sheet of paper) or (2) changes in measureable physiological features (e.g., increased blood pressure, sweating).
Sixth, if one’s thinking something merely consists in being disposed to move in certain ways given certain sensory inputs, then one would have no idea what it was he was thinking about until the movement disposition was manifested through his body. But surely one knows what she is thinking about before she acts and she knows her own thoughts, not by observing her own bodily actions, but through direct introspective awareness of her own states of consciousness.
Finally, two further criticisms have been raised against philosophical behaviorism. Since many philosophers believe that these criticisms apply equally to all forms of physicalism, they will be mentioned here and not repeated in detail later. But you should remember that, if successful, they apply to the other forms of physicalism listed below. For one thing, philosophical behaviorism seems to imply some form of determinism and a denial of libertarian freedom of the will. We will probe questions of freedom and determinism in chapter fifteen, but for those who think that libertarian freedom is true and determinism is false, this will count against philosophical behaviorism. And employing an ontological interpretation of quantum physics (the quantum world really is indeterministic) may get rid of the determinism problem, but it seems to be the cure that kills the patient. Why? Because a strictly random indeterminate event—say one’s arm randomly and in an indeterminate way just jerks up and hits someone in the face—is not one that results from an act of libertarian free will. By the way, don’t confuse the inadequacy of quantum indeterminism in giving us libertarian freedom because it rules out determinism with the attempt to use quantum indeterminism to show how libertarian actions could occur without violating deterministic laws of nature. The latter is a legitimate research program, but the former is a dead end.
Second, philosophical behaviorism (along with other versions of physicalism) seems to imply a denial of a unified self at a point in time and an enduring self that remains literally the same through change. This point will be developed more fully in chapter thirteen, but for now it should be noted that if physicalism does, in fact, imply a denial of a unified and enduring self and if there is good reason to believe in such a self, then this raises a difficulty for physicalism in any form. These last two points illustrate the fact that many philosophers have seen an intimate connection between philosophy of mind and the dualist-physicalist debate, on the one hand, and issues in freedom and determinism and in personal identity, on the other.
2.2 Type-Type Identity Theory (Hardware View #1)
In order to understand the type-type identity theory, it is important to be clear about the difference between a type and a token (see chap. 10). A type is a general kind of thing that can be in more than one place at the same time or at the same place at different, interrupted times. When pain is considered as a type, it is being viewed as a general kind of state that can be in different organisms at the same time or the same organism at different times. By contrast, a token is an individual, particular instance of a type. A pain token is a specific dated instance of the general kind of state known as a pain type state.
Advocates of the type-type identity thesis claim, first, that each type of mental state (e.g., a pain type state or a type of state in which one is thinking that 2 + 2 = 4) is identical to (the very same thing as) a certain brain type state, say a certain pattern of neurons firing. This position is therefore called a hardware view because types of mental states are identical to types of physical stuff or “hardware” in the brain and central nervous system.
Second, advocates of this view claim that the identity between a type of mental and physical state is a contingent identity (see chap. 9). In philosophical behaviorism, the term pain is identical to some term expressing a tendency to engage in some overt movement, and the identity is analytic or true in virtue of the meaning of the terms used in the identity statement. By contrast, a contingent identity statement is one that uses two terms with different meanings but that, nevertheless, refer to the same thing as a contingent fact. For example, in the statement “The Evening Star is identical to the Morning Star” or “Heat is identical to the motion of molecules,” the terms in the statements do not mean the same thing but they do (allegedly) refer to the same thing. Further, the Evening Star could have turned out to have been a different planet than the Morning Star, but as a contingent matter of fact, an empirical discovery showed that the two terms “the Evening Star” and “the Morning Star” refer to the same thing: Venus.
In the same way, terms referring to mental states do not mean the same thing as terms referring to brain states, but as a contingent matter of fact, scientific discoveries (allegedly) have shown that both terms refer to the same thing: a type of neurophysiological state in the brain and central nervous system. The term pain refers to whatever it is in an organism that causes pain behavior, and as a matter of empirical contingent fact, we now know that it is a brain state that pain refers to according to this position. U. T. Place, Herbert Feigl, and J. J. C. Smart are philosophers who have been advocates of the type-type identity thesis.
As with philosophical behaviorism, a number of severe criticisms have been raised against the type-type identity theory. First, types of brain states and types of mental states seem to have very different properties, and therefore they cannot be identical to each other. In this regard, Roderick Chisholm has made the following observation:
Let us consider some particular psychophysical identity statement—the statement, say, that thinking about unicorns is the same thing as to have Q fibres that vibrate in manner N. One cannot understand such a statement, of course, unless one can grasp or conceive the property or properties that are referred to. . . . To the extent that we can understand the statement in question, we can see that the two properties referred to are not the same property—just as we can see that the property of believing that all men are mortal is different from that of wondering whether there is life in outer space. It has been held, not implausibly, that to deny the validity of such rational insights is to undermine the possibility of every type of reasoning.
In chapter eleven we looked at some of the differences between mental states and physical states. Mental states are essentially characterized by their first-person, private, inner, subjective qualities (e.g., a pain is essentially characterized by its felt quality, the what-it-is-like to being in pain, an awareness of red by its being a subjective mode of experience, a thought by its internal content that can stand in logical relations to other thoughts), by intentionality, and so forth. By contrast, brain states do not have such characteristics, but rather possess various physical and chemical properties. Thus they cannot be identical.
As a further elaboration of this point, Saul Kripke has pointed out that pains, for example, do not merely happen to be characterized by their subjective, conscious felt quality, but they have this felt quality as part of their very essence. In every possible world, something will count as a pain if and only if it possesses this very type of felt quality. But no brain state or bodily behavior has this felt quality as part of its very essence. Moreover, even if life after death is false, surely it is metaphysically possible. In fact, it is possible for a disembodied person to exist and to think, have certain feelings, beliefs, desires, and so forth. But it hardly makes sense to speak of a brain state that could exist in a disembodied, immaterial mode of existence. Thus mental states and brain states cannot be the same thing.
A second criticism is sometimes called the problem of multiple realization. Take an alleged mental state like a pain type state and call this type of state MS1. According to the type-type identity theory, this type of state is identical to a certain type of brain and central nervous state, BS1, in the human body. But now a problem arises. Presumably dogs, Martians, and a host of other creatures can be in pain, that is, can be in the type of state we have called MS1. But these creatures cannot be in BS1 because they have different hardware states composed of different patterns of physical stuff. Suppose a Martian was not composed of carbon-based chemicals but rather other physical components. Then the Martian could be in certain kinds of brain states, say, BS2, but not BS1, which makes reference to materials constituting humans when they are in pain but which are not part of the Martian constitution. But since a pain type state, MS1, is identical to (is nothing more or less than) BS1, and since Martians cannot be in BS1, then it becomes impossible for Martians (or dogs and other creatures) to be in pain.
Something has gone wrong here, and the dualist has a solution to the problem. For the dualist, Martians can be in pain like humans even though they each have different types of brain states, because pains are not identical to brain states but to states essentially characterized by their conscious felt quality. Functionalism and the token-token identity theory are two physicalist responses to this problem, which we will look at below.
A third problem with the type-type identity thesis is this: science cannot demonstrate that we should prefer the view that types of brain states are identical to types of mental states as opposed to the view that the two states are merely correlated with each other or enter into cause-effect relations with each other even though the two types of states are nonidentical. These two views—mental and brain type states are identical versus mental and brain type states are different yet correlated—are empirically equivalent. Each view is consistent with the same set of scientific observations. In light of the problems with the type-type identity view, the correlation option should be preferred. Moreover, in order to establish such correlations, the scientist must rely on first-person reports as to what is going on in the private, first-person, inner conscious life of the person being studied, but the scientist does not have to rely on such reports to know something about the brain or, indeed, about any physical state whatsoever.
2.3 Token-Token Identity Theory (Hardware View #2)
In order to understand the token-token identity theory, recall the problem of multiple realization. Martians, for example, could be in pain even though they could not be in a type of brain state possible for humans. The property dualist solution to this problem was noted above. But advocates of the identity thesis have a response to it as well: rather than abandon the identity thesis per se, one should modify the type-type identity thesis and embrace the token-token identity thesis.
According to the token-token identity theory, there is no set of general conditions that can be given for identifying a general kind of mental state with a general kind of brain state. Since we have taken reductive physicalism to require that general conditions be stated for identifying mental states with physical states, then the token-token view is not reductive in this sense. But in another sense, the view is reductive. While advocates of the view reject the identification of mental state types and physical state types, they nevertheless accept the fact that for any specific instance of a mental state, that very state will, in fact, be identical to (and in this sense reducible to) some specific instance of a physical state. Individual mental state tokens are always identical to individual physical state tokens even if no general conditions can be stated for identifying mental state types with physical state types.
For example, even though the general mental state called a pain type state cannot be identified with a general brain state type—Martians, humans, and dogs can all be in that mental state type while being in very different brain state types—it is still true that for any specific pain a human (Martian, dog) undergoes, that individual pain will be identical to a specific, individual brain state. Every token of a mental state is identical to a token of a brain state even though no identity can be stated between types of mental and brain states. Recent advocates of token-token identity theory are David Papineau and Cynthia Macdonald.
The token-token identity theory does appear to solve at least part of the problem surfaced in the example of Martian pain. A general type of mental state known as being in pain is not identical to a general brain type state, say, BS1 present in humans. Thus Martians, dogs, and humans could all be in different types of brain states and still be in the type of state we would call a pain type state. This could be true even though each individual instance of pain is identical to a specific brain state token in the Martian, human, or dog.
In spite of this, however, the token-token identity theory has been subjected to several criticisms. Apart from the problem of multiple realization, all the criticisms raised against the type-type identity thesis apply to the token-token identity thesis: (1) For any specific pain, that very pain has properties not true of any brain state, including the one instanced alongside the pain token. (2) It is possible that the very mental state in question (a specific pain, thought, etc.) could have obtained in a disembodied state, but the same is not true of any individual physical state. (3) There is the problem of justifying the preference of identity over correlation.
However, there is a further problem with the token-token thesis that is unique to it: What is it that gives unity to the class of all individual pains? What is it about all pain tokens that places them in the class of pains and not in, say, the class of smells, feelings of love, or some other class? The dualist would say that all pain tokens are members of the type known as pain because each individual pain possesses something in common that is the essence of each pain: a specific type of conscious feeling. But obviously, this move is not available to the token-token identity theorist.
If two people are in the same kind of mental state (e.g., each is in pain) but are in different neurophysiological states, then what is it about those different neurophysiological states that makes them each a token of the same mental state? We have seen that it cannot be the possession of the same felt quality. Neither can it be the possession of the same neurophysiological features because these are different in the case we are considering.
Some advocates of token identity physicalism combine this view of individual mental events with a functionalist view of kinds of mental events. Functionalism will be described more fully below. But for now, the idea is, roughly, that a mental kind, such as a pain type event, is a type of function characterized by certain inputs (e.g., being stuck with a pin) and certain outputs (e.g., shouting “Ouch!” and feeling self-pity). The only events that are allowed to play the functional role are individual brain events.
Unfortunately, this move does not adequately solve the problem of the unity of mental kinds. Why? Because the essence of an individual state must be constituted by the features intrinsic to it (its internal felt quality or its internal physical features) and not by the external relations it sustains to other things (its being caused by a pin prick and its causing certain behavior). Something (like a pain) cannot be related to something else (pin pricks or behavior) unless it first exists and has certain characteristics internal to it (the felt quality that makes up its inner nature). Moreover, the connection between an internal mental state and bodily inputs and outputs is contingent. Surely God could have created Martians such that after they are stuck with a pin and before they grimace and say “Ouch!” they experience not pain but a mental state of pleasure. The problem of the unity of mental state tokens within a mental state type is a serious problem for the token-token identity thesis. Thus it is more reasonable to hold that all pain events are members of the kind “being a pain” due to a feature intrinsic to each event—its hurtfulness—rather than being due to features such as functional roles that are extrinsic to each event in the kind.
2.4 Functionalism (The Software View)
Our final remarks about the token-token identity thesis provide a good transition into a very popular modern version of physicalism known as functionalism. There are different forms of functionalism, but they all have in common the fact that they model mental states along these lines: mental states are functional states of organisms. A popular version of functionalism is an expression of what is called strong artificial intelligence models of the mental: the mind is fundamentally a computer program. We can describe computers according to their hardware or software. When we describe hardware, we make reference to the physical stuff or components that make up a computer. This is similar to what advocates of both forms of the identity thesis do when describing mental states. We can also use an analogy to a computer with a software view by making reference to the different inputs, outputs, and other features of the program that the computer uses to operate. This is analogous to what some advocates of functionalism do with mental states.
For the functionalist, a mental state can be exhaustively described in terms of sensory inputs, behavioral outputs, and other “internal” states. The essential feature of any type of mental state is the set of causal or logical relations its realizer bears to environmental inputs on the body, other types of “mental” states related to the state in question, and outputs understood as bodily behaviors. For example, the mental state of being in pain could be defined as that state which plays the following functional role, which we can call causal role R: the state is caused by certain tissue damage as a result of a pin prick or some other input and, in turn, causes the person to feel self-pity, to desire help and empathy, and to shout “Ouch!” while grimacing and seeking help. An organism is in pain if and only if it is in a state characterized by causal role R according to functionalism. Strictly speaking, functionalism is consistent with dualism because it could be claimed that the state which fulfills causal role R (e.g., the state that is caused by a pin prick, that causes feelings of self-pity and a desire for help, and that causes one to shout “Ouch!”) is an irreducibly mental state internally characterized by the conscious feel essential to a pain. But most functionalists are physicalists and they claim that the states that happen to fulfill causal role R are neurophysiological states of the brain.
Note carefully that according to functionalism the defining traits of a mental state—pains, thoughts, or otherwise—are not the internal, private, conscious qualities of the states themselves known through first-person introspective awareness. Rather, the defining traits of a mental state are the logical or causal relations that obtain among certain bodily inputs, certain bodily outputs, and other “mental” states. It should be clear why one way to spell out functionalism is an artificial intelligence approach to the mental. For a computer to be able to “read mathematics and be able to add,” the computer must be able to receive certain input (“2,” “+,” “2,” “=”), produce certain outputs (“4” is displayed on a screen), and advance to certain other internal states (it is ready to display “8” if you input the command to multiply the new total by 2). Functionalism is very similar to philosophical behaviorism, but whereas the behaviorist sought to define a mental state solely in terms of publicly observable bodily outputs, the functionalist makes reference to whatever it is within the organism that is caused by the inputs and causes the outputs, and the functionalist also makes reference to other “mental” states that are causally connected to the state in question (e.g., a pain state is one that causes, among other things, a feeling of self-pity and a desire for help).
For the functionalist, mental terms like pain get their meaning primarily from the role the term pain plays in a third-person theory used to describe and explain the behavior of others. Thus we use the term pain as part of our theory of why others shout “Ouch!” after they are stuck with a pin. We attribute certain states to others to explain their behavior, among other things. David Lewis and Jaegwon Kim are prominent functionalists.
As with the other physicalist theories, a number of substantive criticisms have been raised against functionalism. The first objection centers on the fact that functionalists make the defining characteristics of a mental state the logical or causal relations of input and output to the organism and not the internal traits of the state itself known directly through introspective awareness.
A standard way to illustrate this first objection is through what is called the problem of inverted qualia (qualia is plural for quale, which means a specific experiential quality—for example, what-it-is-like to experience redness or blueness). Consider two people, Jones and Smith, who both come into a room, scan it with their eyes, sort the red objects from all the rest, and point to the red objects and say, “The red ones are over here.” According to functionalism, Jones and Smith are both in the very same mental state, namely, the state of being aware of redness.
However, it is metaphysically possible that Smith is color normal but Jones has an inverted color awareness: Jones has an awareness of blue every time Smith and everyone else senses red and vice versa. In this case, Smith would be sorting red objects from all the rest based on his mental state of sensing redness, but Jones would do so based on his mental state of sensing blueness. Functionalists claim that Jones and Smith are in the same mental state because they both are in that state caused by certain inputs (scanning the room) and that produces certain outputs (sorting the red objects from the others plus the belief that the word red applies to these objects). But Jones and Smith are not in the same mental state if mental states are characterized by their inner nature: Jones is aware of blueness; Smith is aware of redness. Jones and Smith function the same way based on very different mental states. Since two different mental states are consistent with the same functional states, the latter cannot be identified with the former.
A second, related objection to functionalism is called the problem of absent qualia. According to functionalism, if unconscious machines like computers or robots are able to imitate consciousness by embodying the right functional state, then they are, in fact, in that mental state. But this seems wrong. Even if a robot could be set up to grimace, shout “Ouch!” and so forth after being stuck with a pin, the robot would still not be in the state of being in pain because the specific conscious property of painfulness would be absent.
Another famous example of this problem has been used to show that functionalist accounts of mental states, like thoughts and understanding meanings, do not succeed because they treat such states as being nothing more nor less than functional states like those in a computer. The example comes from John Searle and is known as the Chinese room. We described the example in chapter eleven, but it has played such a prominent role in the present context that it is worth mentioning again:
Imagine that you are locked in a room, and in this room are several baskets full of Chinese symbols. Imagine that you (like me) do not understand a word of Chinese, but that you are given a rule book in English for manipulating the Chinese symbols. The rules specify the manipulations of symbols purely formally, in terms of their syntax, not their semantics. So the rule might say: “Take a squiggle-squiggle out of basket number one and put it next to a squoggle-squoggle sign from basket number two.” Now suppose that some other Chinese symbols are passed into the room, and that you are given further rules for passing back Chinese symbols out of the room. Suppose that unknown to you the symbols passed into the room are called “questions” by the people outside the room, and the symbols you pass back out of the room are called “answers to the questions.” Suppose, furthermore, that the programmers are so good at designing the programs and that you are so good at manipulating the symbols, that very soon your answers are indistinguishable from those of a native Chinese speaker. There you are locked in your room shuffling your Chinese symbols and passing out Chinese symbols in response to incoming Chinese symbols. . . . Now the point of the story is simply this: by virtue of implementing a formal computer program from the point of view of an outside observer, you behave exactly as if you understood Chinese, but all the same you don’t understand a word of Chinese.
The Chinese room with the person inside would simulate a computer to an outside person and represents a functionalist account of mental states like thinking and understanding meaning. For a person outside, the room receives input and gives output in a way that makes it appear that the room understands Chinese. But of course, all the room does is imitate mental understanding; it does not possesses it. Computers are just like the Chinese room. They imitate mental operations, but they do not really exemplify them.
Third, functionalists have difficulty accounting for the unity of a class of mental states. We surfaced this type of objection in connection with token-token identity theory. Consider the class of all pains of a specific type. The unity of that class, the thing that makes all pains members of that class, seems to be something internal to each member: the fact that they all have the same inner nature, the same qualitative subjective feel. It does not seem that each pain was caused by the same type of input (e.g., a pin prick), that each pain caused the same type of output (e.g., “Ouch!”) and other “mental” states (e.g., a desire for pity). These causal relations are related externally to the pains themselves. They are contingently connected with pains—there could be pains without these causal connections. And the causal relations could be interconnected with other mental states like sensations of pleasure. God could have made us such that we experience pleasure after being stuck with a pin and before grimacing and shouting “Ouch!” Thus these causal connections do not constitute the essence of pains. In general, the essence of a mental state is its inner, mental nature, not the external causal relations that the state sustains to bodily inputs, outputs, and other “mental” states.
2.5 Eliminative Materialism
The last form of physicalism to be considered is, perhaps, the most radical and is called eliminative materialism. To understand it, we should first remember a point made in chapter nine about theory replacement in the history of science. Sometimes a new theory replaces another theory as oxygen theory replaced phlogiston theory. In cases like these, the replaced theory is abandoned and the entities postulated as real in the theory are no longer believed to exist. Several entities once thought to exist are no longer taken as real: the aether, phlogiston, and caloric. These entities have been eliminated in favor of new entities postulated by advocates of the theories replacing the old ones.
Now advocates of eliminative materialism believe that terms that appear to refer to mental states—pain, a belief that P—are like the terms phlogiston and aether. They were part of an inadequate theory that should be abandoned in favor of a better theory. The inadequate theory is sometimes called folk psychology, and the better theory is one that comes from neurophysiology. On this view, folk psychology is a theory that uses terms referring to mental states to offer commonsense explanations for the behavior of people (and certain animals). Here are some commonsense generalizations of folk psychology that use such mental terms: People in pain tend to grimace. People who feel thirst tend to want to drink fluids. Consider the first sentence. This sentence is part of a theory that explains the behavior of people. If we ask why Mary has just grimaced, we can explain this by saying that all people who feel pain tend to grimace, Mary is in a mental state known as an experience of pain, and, therefore, Mary is grimacing.
Unfortunately, argue eliminative materialists, we now know that the states causing Mary to grimace and, indeed, all the alleged mental states postulated in folk psychology, do not exist. Instead, what causes Mary to grimace is that such and such C fibers are vibrating in a certain manner in Mary. In general, folk psychology is false, and its conception of the mental should be abandoned and replaced by a better theory that uses only terms that refer to physical states. Eliminative materialists do not believe that mental states should be reduced to brain states any more than scientists believed that phlogiston should be reduced to oxygen. There are no mental states at all (or at least no thoughts, beliefs, or desires; maybe sensations exist). No one has ever been in a mental state of pain, of having a thought or belief, or sensing something. Richard Rorty and Paul Churchland are two recent advocates of eliminative materialism.
The main criticism of eliminative materialism centers on the fact that it is simply obvious through introspective awareness of our own conscious lives that mental states like thoughts, pains, and desires exist and have the natures they present themselves to us as having in such introspective acts. Eliminative materialism denies this fact and is, therefore, to be rejected. In fact, eliminative materialism has the wrong picture of the mental life and the terms we use to describe it. For one thing, the main focus of the mind-body problem is mental states themselves (e.g., pains), not the mental terms (e.g., pain) we use to talk about them. Thus even if we grant that our use of the term pain derives from folk psychology, pain itself does not. Pain itself is not part of a theory, but rather is a mental event with a certain characteristic feel made available to us in acts of self-awareness. It is hard to see how any advance in scientific knowledge could be the least bit relevant to the question of whether we are directly aware of pains, desires, and so forth.
Furthermore, it could be argued that mental terms like the term pain are not primarily terms that play a role in a third-person theory (folk psychology) that attempts to explain the behavior of others first and, by extension, one’s own behavior. Rather, pain is primarily a term we use to report to others an experience we are having, and pain is ostensibly defined by our own acquaintance with pain itself. Since pain is primarily a term used to report something and not to explain anything, it is hard to see how any explanatory theory at all (e.g., neurophysiological theory) could replace it, since basic mental terms are not primarily or simply terms used in explanation. And when we do, in fact, use pain to explain the behavior of others, we attribute to them an internal mental state analogous to the one we feel when we are in pain. Strictly speaking, this use of pain to explain the behavior of others is complementary to neurophysiological explanations of that behavior, since the two could both be true descriptions of different aspects of what happens when someone is in pain. In such cases a mental pain state is exemplified in the person’s soul and a certain brain state is exemplified in the person’s body. These points are not limited to sensations such as pains, but also apply to thoughts, beliefs, and desires.
2.6 Nonreductive Physicalism
Nonreductive physicalism is becoming increasingly popular, so we want to finish this section by offering a few words about the view. To do this, we must start with a brief discussion of strong property supervenience. (There are also global and weak property supervenience, but they are less relevant to our present topic, so we set them aside.) Strictly speaking, strong property supervenience is just a way of expressing the covariance between two different kinds of properties. If property A (say, wetness) supervenes on property B (say, the property of being a certain structural arrangement of water molecules)—in this case, A is at the supervenient level and B is at the subvenient level—then, necessarily, (1) if B is exemplified, that is sufficient to ensure that A is also exemplified and (2) property A can disappear or be replaced with some other property C at the supervenient level only if there is a change at the subvenient level such that B is no longer exemplified. By itself, supervenience does not include the notion that one property at the supervenient level, say A, is caused by or ontologically dependent on its subvenient base (B). But most philosophers pack a notion of dependency into supervenience, so we will follow this tradition. Now let us look at the mental supervenience thesis.
According to the mental supervenience thesis, mental properties supervene on physical properties, in that, necessarily, any two things (in the same or different possible worlds) indiscernible in all physical properties are indiscernible in mental properties.
This thesis says that once the physical properties of a possible world are fixed, then the mental properties that depend on the instantiation of the relevant physical properties for their instantiation are fixed as well, in that and other possible worlds. Think of it this way. Suppose God created a world with various objects, and then distributed brains to a number of those objects and caused all those brains to be alike in exemplifying the same physical property, say, being a C fiber firing. God would not have to take a further step and distribute the property of painfulness in just those objects that have the property of being a C fiber firing. No, there is something about the very nature of being a C fiber firing that it “brings along with it” a second property that depends on it, namely, being painful. Once the physical is fixed, so is the mental.
One more point of clarification. In the mental supervenience thesis, the word necessarily occurs. What does it mean? It can mean either de re metaphysical necessity or nomological necessity. According to the first, there is something about the very essence of being a C fiber firing that it must bring being painful with it. Just as there is no possible world with Socrates in it and he is not human, or no possible world with water and no H2O, so there is no possible world with being a C fiber firing with no painfulness. Their connection is one of deep metaphysical necessity. By contrast, nomological necessity only ranges throughout those possible worlds that are minimal physical duplicate worlds, that is, worlds that are exactly alike physically—particle by particle, physical property or relation by physical property or relation, laws of nature by laws of nature. Here, the idea is that in our world and all worlds that are exactly like ours physically, if being a C fiber is instantiated, being painful will be as well, but only throughout all minimal physical duplicate worlds. This is consistent with there being a possible world that is not like our world in which painfulness is instantiated but being a C fiber firing is not. Nomological necessity is weaker (it ranges throughout fewer possible worlds) than metaphysical necessity.
The important thing to keep in mind is that in one way or another, the physical properties of a world, especially of the brain, fix the mental properties of the brain because the latter depend on the former.
There are three different kinds of properties that are involved in three different types of supervenience. The first is a functional property: F is a functional property = def. F is a functional concept that is constituted by role R. Moreover, F supervenes on some entity e if and only if e plays (realizes) role R. Some have argued that there are no functional properties that characterize things in the mind-independent world. Rather, functional “properties” are functional concepts, ways of describing or taking something for certain purposes. For example, a certain piece of paper exemplifies being rectangular, but it realizes the functional concept “being a dollar bill.” One virtue of this approach is that it simplifies our ontology when compared to a more abundant view of properties. On an abundant view, a dollar bill actually has the property of being a dollar bill that, in turn, could be identified with the property of being such as to play role R (a role in economic exchanges of goods and services). And in the right circumstances, people would also take a certain piece of paper to play role R by having the concept of playing role R.
This kind of supervenience is called conceptual supervenience: when the subvenient level is arranged appropriately (e.g., to form a certain rectangular piece of paper), we can use a new concept for the subvenient level, for example, being a dollar bill. This kind of supervenience is very much in keeping with functionalism, and indeed, it is safe to say that many functionalists would consider conceptual supervenience as an essential component of their view. A nonreductive physicalist of this sort would hold that types of mental concepts (e.g., writing a greeting) cannot be reduced to types of physical concepts (e.g., the concept type being a certain brain state that caused the body movement of scribbling on a piece of paper). However, such a view does not embrace the reality of irreducible phenomenal consciousness as was defended in the previous chapter.
To understand the other two kinds of supervenience, it will be helpful to clarify the difference between emergent and structural properties and supervenience. An emergent property is a completely unique, new kind of property different from those that characterize its subvenient base. Accordingly, emergent supervenience is the view that the supervenient property is a mereologically simple, intrinsically characterizeable, novel property different from and not composed of the parts, properties, relations, and events at the subvenient level. This type of supervenience is sometimes called causal supervenience. A nonreductive physicalist of this sort would embrace the existence of irreducible, phenomenal consciousness and, accordingly, would be a mere-property dualist.
By contrast, a structural property is one that is constituted by the parts, properties, relations, and events at the subvenient level. A structural property is identical to a configurational pattern among the subvenient entities. It is not a new kind of property; it is a new pattern, a new configuration of subvenient entities. This type of supervenience is often called constitutive supervenience because the supervenient entity is simply composed of a new arrangement of the entities at the subvenient level. For example, being H2O structurally supervenes on hydrogen and oxygen when they are in the proper structural arrangement. Here, the hydrogen and oxygen constitute the essence of being H2O since the latter just is the former in a new arrangement. A nonreductive physicalist of this sort embraces new relational structures, but does not accept any genuinely new emergent properties.
In sum, the only version of nonreductive physicalism that embraces phenomenal consciousness is the one associated with emergent supervenience.
We close this survey of physicalist strategies with a statement by John Searle:
Earlier materialists argued that there aren’t any such things as separate mental phenomena, because mental phenomena are identical with brain states. More recent materialists argue that there aren’t any such things as separate mental phenomena because they are not identical with brain states. I find this pattern very revealing, and what it reveals is an urge to get rid of mental phenomena at any cost.
3—The Main Intellectual Drive Behind Physicalism
What is behind this urge to get rid of mental phenomena? This issue has already been touched on in the introduction to the chapter, but we will conclude this chapter with a few more remarks about this question. Three broad kinds of reasons are offered for physicalism over against dualism. First, it is argued that when the details of the positions themselves are examined, some version of physicalism is simply more plausible than versions of dualism. For example, dualist treatments of pain are just not as reasonable as some version of physicalism, given what we actually know about pain. Since the main thrust of this and the previous chapter was to present these different positions, we leave it to the readers to examine them again and judge for themselves as to which one is more reasonable given what it is reasonable to believe about pains, thoughts, and so on.
Second, there are general philosophical arguments given either against dualism or in favor of physicalism. Two of these were briefly mentioned in chapter eleven—the problem for dualism of how and where interaction between mind and body takes place and the use of Ockham’s razor to raise simplicity considerations in favor of physicalism—so we will not repeat our discussion of them here. There are two other major philosophical arguments against dualism: the problem of many minds and the problem of other minds. Let us look at these in order.
The problem of many minds is this: If dualism is true and the mind and body are different, then why would we expect that there would be just one mind attached to one body? When we meet a person, how could we ever know that the body before us had only one mind in it instead of seventeen minds? Since dualism cannot rule out the possibility of many minds, dualism leads to skepticism about our knowledge of how many minds others have, and thus it is to be rejected.
Four responses can be given to this problem. First, since dualism allows for the possibility of many minds in one body, and since such a state actually occurs in cases of demon possession, then the dualist allowance of this possibility is a virtue, not a vice. Second, as we saw in chapter four, from the mere fact that a position makes skepticism logically possible, it does not follow that skepticism is reasonable or that we do not have knowledge in the area in question. While we cannot rule out the many minds possibility in an a priori fashion, nevertheless, based on inductive experience with our own consciousness and the lives of others, we are entitled to claim that someone else has only one mind attached to one body unless there is evidence (e.g., in demon possession cases) to the contrary. Third, if some version of substance dualism in the tradition of Aristotle or Aquinas is correct, then the soul (perhaps by using DNA molecules) is what makes the body and gives the body its nature (e.g., your body is human because it is informed by a human soul). The soul provides the form or essence of the body; the body is dependent on the soul for its coming into being and not vice versa. This intimate connection between one soul and one body gives us a model that justifies the expectation that there will only be one soul that is the owner of one body. In demon possession cases, the demon does not provide the essence of the body but merely inhabits it. Finally, physicalists have their own problems accounting for the unity of consciousness at a point in time and the unity of consciousness through change. This is why physicalists concentrate their efforts on mental events and usually bypass issues about the metaphysics of substance. This point will be developed more fully in chapter fourteen.
The problem of other minds is this: If dualism is true, we can never know that other people have mental states because those states are private mental entities to which we have no direct access. In this regard, dualism implies skepticism in two ways: it leaves us skeptical as to whether other minds exist in the first place, and even if they do, it leaves us skeptical as to what other persons’ mental states are like. Perhaps they have inverted qualia compared to me—they sense redness and joy when I sense blueness and pain and vice versa. If dualism is true we could never know.
The dualist problem of other minds has been greatly exaggerated. Our response to this problem is similar to what was said in regard to the problem of many minds. First, dualism does, in fact, imply the following: from what we know about a person’s brain, nervous system, and behavior, we cannot logically deduce his or her mental states. But, again, far from being a vice, this implication seems to be the way things really are. Even young children occasionally wonder if they may sense colors in a way different from others. In general, it is in fact logically possible for one person to be in one kind of mental state and another person to be in a different kind of mental state even though their physical states are the same.
Second, the logical possibility just mentioned does not imply skepticism about other minds. We do not know something only if it is logically impossible that we are wrong about it. There are many dualist views as to how we have knowledge of other minds—for example, we postulate that others are in pain when we observe them stuck with a pin and grimacing as a simple inference to the best explanation of these facts or based on an analogy with what we know we would be experiencing in a similar situation. But regardless of how we explain our knowledge of other minds, we do, in fact, have such knowledge, and the mere logical possibility that we are wrong about the mental states of another is not sufficient to justify skepticism.
In our view, the real intellectual driving force behind modern physicalism is not the philosophical case for it and against dualism, but a cultural commitment to naturalism and to scientism. As Lynne Rudder Baker points out, “Physicalism is the product of a claim about science together with a particular conception of science. The claim is that science is the exclusive arbiter of reality. . . . On this view, scientific knowledge is exhaustive.”
If the space-time physical world of objects studied by science is all there is, and if science is our best or, perhaps, only rational way of gathering beliefs about the world around us, then, according to most physicalists, dualism must be false. Why? Because the existence of mental states or immaterial souls threatens the unity of science, especially the adequacy of chemistry and physics, to explain all of reality. Thus naturalism and scientism would be false.
Several alleged scientific objections have been raised against dualism. Actually, these objections do not come from science per se, but from what some philosophers tell us science must say. First, some have argued that mental entities are simply metaphysically odd and extravagant. But odd to whom? The soul and consciousness are very much at home in a theistic worldview because such a perspective regards mind as more fundamental than matter. The soul is bizarre only if you already presuppose naturalism and scientism.
Second, others have argued that if mental states exist and can cause things to happen in the world, then this violates the fact that the physical universe is “causally closed,” that is, any event that happens is solely the product of other physical factors that are sufficient to cause it. There are no causal influences on physical events besides other physical events. Sometimes this problem is put in terms of the first law of thermodynamics, also called the conservation of energy principle. This principle states that the amount of energy in a closed system remains constant. But if there is causal interaction between the mental and the physical, then certain physical effects are not solely the product of other physical factors and energy is introduced into the system by mental causality, violating this principle.
Dualists have offered a number of responses to this objection. First, this objection, if correct, eliminates libertarian freedom of the will, and if such freedom exists, then the objection fails (see chap. 15). Second, this objection, if correct, would rule out direct, miraculous interventions of God into the world, and if there is reason to believe in such interventions, the objection fails.
Third, the first law is formulated only for “closed systems,” that is, those without outside interference. Moreover, the first law is formulated only for systems that are wholly material in nature. The dualist points out that, strictly speaking, the first law only applies to totally material, closed systems and not to systems that involve mental causal influence. When a person acts, new energy may be created, but this is a fact that is outside the scope of the first law and not a violation of it.
Still, one could argue that there have been no empirical observations of the creation of new energy in human acts, so this dualist assertion seems dubious. Two responses may be given to this counterargument. First, one may agree that while the creation of energy resulting from agent causation should be easily measurable, and thus libertarianism may be falsifiable in principle, in actual practice, no one has tried to do the relevant investigation, and it is not entirely clear exactly how such a thing should be measured.
Second, it may be that an exercise of free active power involves a very little, virtually undetectable amount of energy, especially as compared to the energy involved in the entire act of, say, raising one’s hand to vote. Perhaps the energy released in the exercise of free active power is miniscule compared to the potential energy released in the body as part of the relevant causal pathway. If this were so, then it may be very difficult, if not impossible, to measure the energy created by exercises of free active power.
There is a third and final scientific objection often raised against dualism. Given the standard scientific account of how the world, in its present form, got here from the big bang through evolutionary processes, there is neither need nor room to fit into this picture the appearance of mental properties or substances. Living organisms, including humans, are solely the result of physical processes operating on physical materials, and thus the product of such mechanisms will be solely physical.
It is well known that one of the driving forces behind Darwin’s exposition of evolution was materialism regarding the mind-body problem. As Howard Gruber explains:
The idea of either a Planful or an Intervening Providence taking part in the day-to-day operations of the universe was in effect a competing theory [to Darwin’s version of evolution]. If one believed that there was a God who had originally designed the world exactly as it has come to be, the theory of evolution through natural selection could be seen as superfluous. Likewise, if one believed in a God who intervened from time to time to create some of the organisms, organs, or functions found in the living world, Darwin’s theory could be seen as superfluous. Any introduction of intelligent planning or decision-making reduces natural selection from the position of a necessary and universal principle to a mere possibility.
Daniel Dennett notes that “Darwin saw from the outset that his theory had to include an entirely naturalistic account of the origins of ‘mind,’ . . . for if Man were to be the golden exception to Darwin’s rule, the whole theory would be dismissible.” The most reasonable way to do this is to advance some version of strict physicalism because if something like mental states or substances exist, there would be one thing about living organisms beyond the explanatory scope of evolutionary theory, and this would threaten to make that theory less plausible. The mere claim that mind simply emerges from matter in the evolutionary process is an unfalsifiable assertion at best, and not one that fits naturally into a Darwinian understanding of our origins.
This same point has been made from Darwin’s time to the present. Here are some recent examples. Paul Churchland makes this claim:
The important point about the standard evolutionary story is that the human species and all of its features are the wholly physical outcome of a purely physical process. . . . If this is the correct account of our origins, then there seems neither need, nor room, to fit any nonphysical substances or properties into our theoretical account of ourselves. We are creatures of matter. And we should learn to live with that fact.
D. M. Armstrong asserts the following:
It is not a particularly difficult notion that, when the nervous system reaches a certain level of complexity, it should develop new properties. Nor would there be anything particularly difficult in the notion that when the nervous system reaches a certain level of complexity it should affect something that was already in existence in a new way. But it is a quite different matter to hold that the nervous system should have the power to create something else, of a quite different nature from itself, and create it out of no materials.
Arthur Peacocke agrees:
I find it very hard to see why that functional property [consciousness] coded in a certain complex physical structure requires a new entity to be invoked, of an entirely different kind, to appear on the scene to ensure its emergence. How could something substantial, some substance or some other entity different in kind from that which has been evolved so far, suddenly come in to the evolutionary, temporal sequence?
Since things do not come into existence out of nothing, if naturalism is correct, then the chemical and physical properties that describe matter should be all there is because such properties are all that was there to begin with. The emergence of different kinds of entities, especially, as noted by Armstrong above, those so different as to be characterized as mental, would either involve the emergence of these new kinds of entities from nothing or from latent mental potentialities in matter.
The first option violates the principle that things do not come into existence out of nothing. The second violates the nature of naturalism since it implies that mental properties are ultimate in the universe as potential properties of matter that emerge when matter is organized in certain ways. This is a major reason for embracing physicalism in the first place, and it is also why the most consistent form of physicalism will define physical in terms of what can be described solely in the language of chemistry and physics. If we need to use descriptions of “emergent” properties that go beyond what the naturalist believes existed shortly after the big bang, the metaphysical status of such properties is a problem.
Some philosophers, like Richard Swinburne, have argued that the existence and nature of consciousness cannot be explained by science and that the best explanation for the existence of finite mental states or souls is the existence of a Grand Soul who created them. This does seem to be a reasonable argument, though we cannot develop it here and not all philosophers have agreed with it. But the fact that there may well be a clear, defensible connection between dualism and theism, and that the existence and nature of the mind is best explained by theism and is hard to square with physicalist versions of naturalism, gives us a broader perspective in which to understand much of the intellectual drive toward physicalism. Dualism is a test case between a naturalistic and a theistic worldview. The existence of mental entities is not equally at home in these two worldviews. Often there is more at stake in the dualist-physicalist debate than meets the eye. In light of this, we close this chapter with a statement from Howard Robinson:
[William] James called materialism a tough-minded theory. We began this essay by wondering why, if this is so, materialists are so often on the defensive in philosophy. The explanation seems to be that though the materialist makes a show of being tough-minded he is in fact a dogmatist, obedient not to the authority of reason, but to a certain picture of the world. That picture is hypnotising but terrifying: the world as a machine of which we are all insignificant parts. Many people share Nagel’s fear of this world view, but, like Nagel, are cowed into believing that it must be true. . . . But reason joins with every other constructive human instinct in telling us that it is false and that only a parochial and servile attitude towards physical science can mislead anyone into believing it. To opt for materialism is to choose to believe something obnoxious, against the guidance of reason. This is not tough-mindedness, but a willful preference for a certain form of soulless, false and destructive modernism.
Chapter Summary
Currently, physicalism is the major rival to dualism. There are two main physicalist strategies regarding consciousness and mental properties/states: reductive and nonreductive physicalism. In the former, an attempt is made to give general, reductive, necessary, and sufficient conditions for any type of mental state in physical terms. In the latter, no such attempt is made. There are two main versions of reductive physicalism: philosophical behaviorism and type-type identity theory. There are three main versions of nonreductive physicalism: functionalism, token-token identity theory, and eliminative materialism.
Each version of physicalism was defined and evaluated. Two problems present themselves to all versions of physicalism. First, physicalism denies full-blown, libertarian freedom of the will. Second, physicalism has difficulty allowing for the unity of the self at a given time and the sameness of the self through change. Philosophical behaviorism is the view that mental terms are to be operationally defined in terms of stimulus inputs and publicly observable bodily behavior or tendencies to such behavior. Type-type identity theory identifies types of mental states with types of “hardware” or brain and central nervous states. Functionalism defines types of mental states in terms of the causal connections that obtain among sensory inputs, behavioral outputs, and other “internal” states of the organism. Token-token identity theory denies the existence of general identity conditions between types of mental and physical states but advocates the identity of individual mental and physical state tokens. Eliminative materialism denies the reality of the mental altogether by treating the mental terms in what they call folk psychology like phlogiston or other terms in a discarded scientific theory. And three versions of nonreductive physicalism were presented. Objections were raised against each view.
The chapter concluded with a survey of the three broad kinds of reasons offered for physicalism: the general superiority of some version of physicalism compared to dualism, philosophical difficulties with dualism (causal interaction, Ockham’s razor, the many minds objection, and the problem of other minds) and arguments from science (the oddness of the mental, dualist violations of the first law of thermodynamics, and the difficulty of accounting for the origin and nature of the mind given a naturalistic account of our origins). Arguments from scientism and naturalism are the primary driving force behind modern physicalism, which illustrates that the mind-body problem is a lightning rod for a broader worldview clash.
Checklist of Basic Terms and Concepts
absent qualia
causal supervenience
Chinese room
conceptual supervenience
constitutive supervenience
de re metaphysical necessity
eliminative materialism
emergent supervenience
folk psychology
function role
functionalism
hardware view
inverted qualia
mental supervenience thesis
mental token
mental type
methodological behaviorism
minimal physical duplicate worlds
multiple realization
nomological necessity
nonreductive physicalism
operational definition
philosophical behaviorism
problem of many minds
problem of other minds
realizer
reductive physicalism
software view
strong artificial intelligence
strong property supervenience
structural properties
subvenient level
supervenient level
token-token identity thesis
type-type identity thesis