presented to the Faculty of the Dominican School of
Philosophy and Theology in partial fulfillment of
the requirements for the degree
of Master of Arts in Philosophy, Berkeley, California, March 2006.
From http://www.opwest.org/Archive/2006/FadokThesis.doc. See profile here.
The purpose of the present work is to show the untenability of the leading efforts made so far towards a reductive materialism in Anglo-American analytic thought, and then to seek some relief in the exploration of positive arguments in favor of antimaterialism that might show promise as capable of engagement in contemporary discussion. Chapter 1 will review the history of the last century or so of philosophy of mind in the English-speaking world. The contention is that the predominant materialist points of view that have arisen to the present time suffer from the same problem, namely, that they operate under the categories and assumptions of the very view their proponents are so confident about supplanting: substance dualism. This has also been the thesis of analytic philosopher John Searle. His views will be considered independently in the chapter, as Searle’s take on affairs is peculiar to him, and unlike many, he demonstrates a genuine appreciation of how bad things are in the philosophy of mind and how they got that way.
The first attempt at a positive argument for making the case in favor of antimaterialism will be based on the nature of consciousness and the so-called explanatory gap. It will be demonstrated that there is no necessary incompatibility between materialism and the existence of an explanatory gap, since the gap in explanation may be seen as representing a gap in our understanding of consciousness, and not in reality. This being so, one cannot count on deriving an antimaterialist position from the existence of the gap. The foregoing is covered in Chapter 2.
Chapter 3 will move us on to proofs for the immateriality of the intellect in the Thomistic tradition. Three proofs will be offered. The first proof, from the capacity of the intellect to know all things, shows initial promise, but cannot finally be preserved from its own failures. The last two, however, show promise as worthy of thoughtful reworking that might make them attention-getters in the contemporary situation. The first of these, from the fact that the operation of the intellect has as its object abstract universals, will be offered in two versions. The first version might be further developed, it will be suggested, in ways that can help plug it into the vast network of competing theories in the unsettled area of philosophy of mind today dealing with the nature and disposition of concepts. The second version is already engaged in contemporary issues about meaning and questions of ambiguity. The final argument, from the self-reflexivity of thought, seems ideally suited for adaptation to current concerns and interests, and might be expected to achieve the most exciting results, since it delves into a common theme in the intellectual life of our so-called postmodern times: self-referentiality.
Modern thinking about the mind tends to go in one of three directions. These three directions by no means exhaust the logical possibilities, but they seem to be the ones that get the most attention. First there are those who think that as persons we are really two things with two kinds of properties. We are a mental thing with mental properties and a physical thing with physical properties. This view, known as substance dualism, is a version of antimaterialism, the idea that there is more to the world than physical stuff, or particles in fields of force, or atoms in the void—choose your favorite expression for the alternative prospect, which we will call materialism. In any case, substance dualism is rare these days.
Next are those who think that as persons we are really one thing with two kinds of properties. We are a physical thing with physical and mental properties. In other words, a person is one two-sided thing. This view, known as property dualism, has been on the rise. Property dualism floats somewhere between materialism and antimaterialism, because most proponents are materialists in the sense that they believe there are only physical things in the world, but antimaterialists in the sense that they believe that some physical things can have mental properties that are irreducible to any physical properties or things. The property dualist is committed to the view that a complete physical description of the world would have to leave out some facts about our mental life.
Finally, there are those who think that as persons we are really one thing with one kind of property. We are a physical thing with physical properties. In other words, a person is one one-sided thing. This is the strictly monist point of view that is commonly called materialism, and, while it may be that this view predominates in most scientific and in many philosophic circles, it may also be true that it is on the decline, at least in many of its explicit philosophical forms. It is to these forms of materialism in the school of thought known as Anglo-American analytic philosophy that we turn the greater part of our attention in this chapter.
Although the bulk of this chapter is a survey of contemporary materialist approaches to philosophy of mind, we must begin with a discussion of dualism. We will focus primarily on substance dualism, because of its tremendous role in the intellectual history of modern philosophy and in Anglo-American thinking about the mind in particular, but we will also have a brief look at property dualism for the sake of completeness. The broad claim is that substance dualism has been enormously influential, and remains so, though in a more covert way. This survey will show (1) that the absolute categories of substance dualism—the mental and the physical—and the assertion of their thorough divorce are still with us, and (2) that the effect of substance dualism on philosophical thinking about the mind in the past century has been lamentable. No doubt there have been many forces at work in the rise of materialism in philosophy of mind and its various efforts to reduce the mental to the physical. But substance dualism has surely been one of them, and its legacy to us is a real and felt need for something different.
Dualism in the philosophy of mind may be understood to imply that were we to settle upon a description of the universe that included nothing but statements of facts about physical things and physical properties, we would have settled for a radically incomplete description of the universe. A complete description of the universe for a dualist would have to include, in addition to statements about all the physical facts, more statements about certain facts that cannot be understood in strictly physical terms: mental facts. The dualist would insist that we cannot reduce the mental to the physical. We cannot understand our mental life to be such that it might be subsumed under the latest theory of physics, chemistry, or biology. The mental is irreducible to the physical; the two are metaphysically distinct.
Among dualists, there are two varieties. There are those who think that there are both mental substances with mental properties and physical substances with physical properties. These two substances are absolutely basic, and neither can be understood in terms of the other. For the so-called substance dualist, there are, in a sense, two worlds: the mental and the physical. A second variety of dualist is the property dualist. There is one world for the property dualist, a world of physical things. However, these physical things have both mental and physical properties at the same time, and the mental properties cannot be reduced to physical things or physical properties. We turn first to substance dualism.
Substance dualism has long been out of favor in Anglo-American philosophy of mind. Yet to this day it has its stalwart defenders whose work is recognized as at least worthy of acknowledgment. Be that as it may, most analytic philosophers do reject it out of hand as untenable, even while some see its influence as perniciously operative even in those materialist theories whose authors would pride themselves on having overcome it. For example, a recurring theme in the work of John Searle is his claim that the reason materialists want to deny the presence of irreducible mental phenomena in the world is, in part, because “they accept the traditional Cartesian categories, and along with the categories the attendant vocabulary with its implications.” I believe this claim is true and that this will become clear in the present survey.
What is substance dualism? Substance dualism in the philosophy of mind is the view that there are two fundamentally different kinds of substances in the world: physical things and mental things. This dualistic outlook has been so frequently associated with René Descartes in philosophic thought since his time that it has come to be known as Cartesian dualism, although it is certainly possible to be a substance dualist without being a Cartesian. One could, for example, hold to the view—decidedly rejected by Descartes—that the body is a container for the mind which in turn pilots the body. This may, in reality, be a very common view among the general populace, but we will proceed to describe this dualism in Cartesian terms, since that is the view that has been so influential in modern philosophy.
When Descartes thought he had discovered that he could be mistaken about just about everything in his experience except for the fact that he was undoubtedly having experiences, he came to the conclusion in his famous, “I think, therefore I am,” that he could be certain of his existence as a thinking thing, and, later, that being a thinking thing is essentially different from being a bodily thing. The latter is evidenced in part by the fact that we cannot be mistaken in thinking we are thinking things, but we can be mistaken in thinking we are corporeal things. Minds, then, are substances characterized by their thinking. Every mind is a res cogitans, a thinking thing, whereas all bodies are characterized by their extension in space. Every body is a res extensa, an extended thing.
The important point is that the thinking thing and the extended thing are two fundamentally and essentially different substances. The difficulty is to show how the two substances can possibly interact, as it would appear they do, given that they are so different. At least the view of the mind as piloting the body like a ship can be crudely pictured. But Descartes must insist that we cannot even say that the mind is within the body, since thinking things have no spatial properties. The “neural dependence” of mental phenomena is another consideration that raises the question of mind-body interaction. It is difficult enough to see how the brain is supposed to function in a Cartesian system as a provider of sensory input to, and receiver of volitional output from, the mind. Worse is the question: If reasoning, emotion, and consciousness really take place in a distinct entity called the mind, then why are they so pervious to brain manipulation, pathology, and damage? This problem of interaction is the root problem with substance dualism. Beyond the particular manifestation of this difficulty in substance dualism, the question of how the mind and the body—whatever they may be—could possibly interact has become known as the mind-body problem.
Substance dualism has had a much more profound influence in the philosophy of mind than property dualism. In fact, property dualism itself is a view that stems from a felt need to somehow reconcile the ostensible claim of modern science that the universe is populated by nothing more than physical bodies with the irresistible insight of the substance dualist that the mental is fundamentally different from the physical and cannot be understood in physical terms. In other words, property dualism is one attempt to solve the mind-body problem.
The property dualist attempts to ride the fence by agreeing that, yes, when it comes to stuff, there is nothing more than physical stuff in the universe. However, the property dualist continues, some physical stuff can have mental properties that are irreducible to the physical. Having a pain, for example, is said to be inexplicable in strictly physical terms.
There is, as one might imagine, an assortment of property dualist theories. According to some, mental properties emerge from complex physical systems of certain types of highly organized structure. For others, mental properties are elemental. In any case, property dualists always have a difficult choice to make. On the one hand, they can claim that mental properties are causally interactive with the physical world. Somehow there is supposed to be causality from the physical to the mental and, likewise, from the mental to the physical. However, explaining this interaction between mind and body is as difficult for the property dualist as it is for the substance dualist. On the other hand, the property dualist might claim that the causality goes in only one direction. The physical causes the mental, but the mental has no effect on the physical. That is, our mental life is epiphenomenal. Alternatively, one might simply say that there is no causal relationship whatsoever between the mental and the physical, and the two simply move along in parallel.  But this view is a bit too flighty for most.
Epiphenomenalism is the form that most contemporary property dualisms take. The idea is that the brain causes mental properties, but they do not in turn have any causal efficacy in the world. Yet this is very problematic. Whereas some epiphenomenalists do bite the bullet, most of us would find it difficult to believe, for example, that we do not remove our hand from the fire because we are in pain, or that we do not vote for our candidate because we believe she will do a good job, or that we do not eat our ice cream because we desire something sweet. In short, most of us believe that our pains, beliefs, and desires, among other things, cause us to behave in certain ways and have real sway in the world.
Despite its own troubles, property dualism has experienced something of a revival in the last decade or so as a response to problems surrounding the nature of consciousness. It has been argued that there is an explanatory gap in our understanding of the world due to the fact that we cannot even conceive of how we might explain the phenomena of conscious mental states in terms of physical theory. This gap, some say, must point to a gap in nature. Property dualism, consciousness, and the explanatory gap, however, are topics for the next chapter. In the meantime, having considered the weighty difficulties of both substance and property dualism, we proceed to the approach that has characterized analytic philosophy in the last century.
Anglo-American philosophy in the past one hundred years has typically regarded antimaterialist dualisms as utter failures in our efforts to know the nature of the mind. In response, the approach to a solution for the mind-body problem that has marked analytic philosophy has been materialism. Materialism, in one form or another, tries to reduce the mental to the physical. The idea is that since we have not been able to make sense out of the notion of mind as a separate substance, unobservable and unreachable, we must find some way to show how our talk about the mind is really talk about physical things and their properties. Somehow we must reduce our mental lives to the stuff that is right there before our eyes.
The version of behaviorism in which we are interested for our purposes here is the philosophical proposal called logical, or analytical, behaviorism. This is not the sort of behaviorism associated with the famous psychologist, B. F. Skinner. Skinner thought that the purpose of psychology is to predict behavior and he was concerned to find an expedient way to do this scientifically. He was not committed to the view that mental states do not exist, just that they are irrelevant to his project. Analytical behaviorism, on the other hand, is a proposal about the meaning of language that is intended to effectively abolish the realm of the mental. Having inherited the frustrating Cartesian conception of the mind as something utterly different from the physical world, with no plausible story about how the two might meet, analytical behaviorists, who wanted a scientific psychology based on observable facts that could be corroborated by any objective third party, opted to eliminate the need to talk of mental substances by translating all verbal expressions about the mind in terms of human behavior and dispositions to behave.
The fundamental doctrine is that any mental predication, for example, “Bob is in pain,” is to be analyzed into a bundle of hypothetical statements about how Bob would behave in various circumstances. “Bob is in pain” means Bob would howl under such and such a set of physical conditions, Bob would throw things under another set of such conditions, Bob would say, “Ouch,” Bob would jump around the room grasping this or that body part, and the like. Since the goal is to translate all sentences referring to beliefs and desires, hopes and fears, and all such mental fixtures, into sentences referring strictly to behavior and other observable physical phenomena, it is crucial to the project that in the final analysis there be no reference at all to mental states or any other unobservables. In this way, it was thought that we could attribute perfectly clear meanings to all of our talk about minds and the mental life, without having to commit ourselves to there being a mysterious and scientifically inaccessible realm of mind-stuff. Behaviorism reduced the mental to the physical by analyzing all talk of the mental into the physical.
Behaviorism is fraught with difficulties. There is, of course, the commonsense objection that it is just silly to deny our human experience that in addition to our behavior there is something else going on inside of us. One philosophical argument based on this sense that there is more to us than behavior is Hilary Putnam’s super-actor and super-Spartan objection. We can imagine an actor so good as to be able to fulfill the requirements of any behaviorist definition of pain without actually being in pain. And we can imagine a person of such Spartan character that he can endure any pain while manifesting not one of the behaviors in the behaviorist analysis of pain.
Another problem is that it turns out that there is an essential reference to interior mental states in our statements about behavior. This is true in at least two ways. First, it is not even possible to define a motion or action on the part of an individual as behavior without some reference to interior states. A mouse jumps around in a cage and we call that behavior. Then the mouse follows exactly the same trajectory, making the very same motions, but this time there’s been an earthquake shaking the cage, and we do not call it behavior. How can we differentiate between the two cases without speaking in some way about the interior mental life of the mouse? Something inside the mouse makes the first case a case of behavior.
Second, a behavioral analysis of a statement about an individual’s mental states, in attempting to eliminate all references to interior activity, will always loop back to such activity. We might say “Bob believes it is raining” means Bob would put on his raincoat if he were to go outside, Bob would close the windows if he were driving his car, Bob would say, “Oh, no, not rain again!” if it is the third day of rain, et cetera. The problem is with the hypothetical conditionals. It is quite impossible to complete them without reference to Bob’s other beliefs and desires, which renders the account circular. “Bob believes it is raining” means Bob would put on his raincoat if he were to go outside . . . if he desires to stay dry . . . and he believes wearing a raincoat will keep him dry . . . and he desires to wear a raincoat rather than carry an umbrella . . . and he believes the raincoat is more readily accessible than the umbrella . . . and on and on.
A final objection to behaviorism is that it leaves out the causal relations between mental states and behavior. If we identify pain with a set of hypothetical pain behaviors, there is one crucial aspect of our concept of pain that is left out. The behaviorist analysis of pain cannot account for our conception of pain as a causal factor in behavior. If pain just is pain behavior, the pain is not causing pain behavior. But we do believe that pains cause behavior, and this is an important part of our concept of pain. Likewise, if we try to equate beliefs and desires with sets of hypothetical behaviors, we fail to attribute to them the causal effects we know they have on behavior.
Like most theories, behaviorism faded away in philosophy not so much because its proponents were convinced of its bankruptcy, but because its proponents themselves were fading away. Fade away they did, and in the meantime, back from the drawing board, philosophers had come up with a proposal that is called the identity theory. Recall that substance dualism had long ago failed because it could not account for the relationship between mind and body. In particular, it could not account for the evident relationship between the mind and the brain. More recently, behaviorism had failed because of its inability to appreciate the essential role of interior mental states in human behavior and mental operations. Motivated, then, by the need to relate mind and body by some reductive theory, while acknowledging the crucial place of interior mental states in a science of the mind, identity theorists proposed that mental states are just states of the brain.
Behaviorism was supposed to reveal analytic truths: mental concepts were supposed to be by definition behavioral concepts, which would make substance dualism logically false. Identity theorists, in opposition, said that substance dualism might have been true, but it just turns out that it is not. It is a matter of contingent fact that mental states are equivalent to brain states. Just as science had discovered that water = H2O, science reveals that mental state x = brain state x. This version of the identity theory is called a type-type identity theory, because it is committed to the view that every type of mental state is equivalent to a type of brain state.
There are a host of problems with type-type identity theories. For one thing, to steal a term from Robert Cummins, they are “neuro-chauvinist.” To have pains, all creatures would require brains like ours. Say that we discover pain = c-fiber firing, the timeworn example in the literature. If we are committed to this view, then we must say that any creature—animal or angel, machine or Martian—that does not have c-fibers cannot experience pain, because pain just is the firing of c-fibers. What if we define pain differently for each species? For humans, pain = c-fibers firing, but for dogs, pain = x-fibers firing, for cats, y-fibers firing, and for Martians, should we meet them, z-fibers firing. Clearly this cannot work, because we would be abandoning our identity theory. If pains are really identical to c-fiber firings, then nothing else can be pain. In order to admit that x-, y-, and z-fiber firings are pains, we would need to use some other criteria other than brain states to say that these creatures are experiencing something like pain as we know it. Maybe we could use their behavior. But then what we are really saying is not that pain = c-fiber firings, but that pain = whatever it is that makes us, and this animal, and that Martian, behave in certain ways. This is a functional definition of pain and it is no longer our identity theory.
A similar problem for identity theory, but this time within the species, is that it just seems so unlikely that for every type of mental state there is one and only one type of neurophysiological state that we all must be in to have it. Even if your belief that Phoenix is the capitol of Arizona is identical with a certain state of your brain, is it really true that I must be in exactly the same neurophysiological state as you in order to believe the same thing? Type-type identity theory is just too strong.
A final case against type-type theories captures the commonsense view that pain has features that brain states do not have. If the identity is supposed to be a contingent truth, then there must be logically independent features of the phenomenon that allow us to identify it in one way on the left side of the equals sign, and in another way on the right. If the phenomenon looked the same to us, so to speak, on the left and the right, then that would be a necessary identity, self-identity, like x = x, and not x = y. For example, pain must have a set of features that allows me to identify it, the brain state must have another set of features that allows me to identify it, and by means of these independent features, we identify each one, the pain and the brain state, and we come to know: Ah! they are the same thing. But now we have a dilemma. Either the features of pain we use to identify it are subjective, introspective, mental features, or they are not. If they are, then the reduction by identity has not worked. Instead, we are property dualists, because what we have is a physical brain state with subjective, first-person mental features. Conversely, if the features we use to identify pain are not subjective, introspective, mental features, then we are treating ‘pain’ as not naming the mental features of the brain state, and we leave it unexplained and mysterious. As with behaviorism, the subjective, introspective, mental features of our experience remain unspecified.
Another version of the identity theory that enjoyed favor for a time in light of the criticisms of the type-type theory above was token-token identity theory. Here the commitment was much less strong than in the type-type theory. Token-token theories said merely that every token of a mental state is identical to some token of a brain state. So two people can have the same mental state and be in different neurophysiological states. But this cannot work. First, it is subject to the final argument above against type-type theories. Second, it has the problem mentioned in the neuro-chauvinist objection above regarding the identification of mental states. Specifically, if two people believe stock prices are high and they have that mental state in virtue of being in some brain state, but the brain states are different, then what makes it the same belief that stock prices are high? Since the aim is to reduce mental features to physical, token-token theorists cannot appeal to mental features for the identification. In order to say what it is that makes two different brain states tokens of the same mental state type, they must appeal to behavior and the functional role that the mental state plays.
Functionalism followed quickly on the heels of identity theory, which enjoyed a surprisingly brief tenure in philosophy, although it would probably not be difficult to find many among educated people today who would be quick to say: Of course the mind is the brain. As we saw above, it is not at all as easy as that, and the problems of identity theory gave birth to functionalism, which inherited the historically conditioned intellectual patrimony of identity theory. This heritage included both the need to account for the relationship between mind and body, which no dualism seemed able to do, especially with respect to the evident relationship between the mind and the brain, and the need to acknowledge the essential role of interior mental states in human behavior and mental operations, which behaviorism had failed to do.
Functionalism, as indicated above, is the definition of mental states according to their causal roles in the subject, both with respect to its behavior and other mental states. The idea is that it does not matter what something is, in the sense of what it is made out of or what its physical structure is; rather, what matters is what the thing does in the system. For example, a carburetor is the device that mixes air and fuel in an internal combustion engine. Of course, it does not just sit there mixing air and fuel. It does so as part of a causal chain that starts with an input, the turning of the key in the ignition, which leads to other events within the system that bring about the carburetor’s mixing air and fuel, which then leads to other events within the system that bring about the motion of the car. What matters is not what the carburetor is made out of, or how its parts are arranged, just so long as it serves to mix air and fuel in the engine as part of the causal chain from input to output. That is its function in the engine and that is what defines a carburetor. Anything that fulfills this function—no matter what it is or how it does it—counts as a carburetor. This feature of functionalism is called multiple realizability, because, sticking with our example, any number of physical devices could realize the role of carburetor in the engine.
Recall the question in token-token identity theory: What makes two different brain states tokens of the same mental type? The answer is that even though our brains realize them differently, what makes my belief that Phoenix is the capitol of Arizona the same as your belief that Phoenix is the capitol of Arizona is that our two different brain states serve the same functional role in the causal chain of events from input, to other mental states, to output. In short, our two different brain states function the same way.
At this point, things are looking fairly good for functionalism. The chauvinism objection that plagued identity theories is overcome by the multiple realizability of mental states. Further, the objections to behaviorism from essential reference to the mental and its failure to recognize causal relations between mental states and behavior are overcome by the acknowledgement in functionalism of causal relations among mental states and behavior. Finally, although within the theory the mind is treated as a black box—no reference is made to features of the states in question, only to their causal roles—when we look at the world, as a matter of fact, it turns out that all mental states are realized by physical states, so the desired reduction of the mental to the physical is still attainable.
There are two major objections to black box functionalism that are related by their common appeal to our experience that there is something it is like to be in certain mental states. It seems that at least some mental states have a subjective feel to them, a qualitative character. There is something it is like to see a sunset, feel a toothache, or quench your thirst. These features are often called qualia in the literature and one argument against functionalism is from the absence of qualia.
The absent qualia argument is usually made in terms of the problem of the inverted spectrum. Suppose that some segment of the population had their color spectra inverted—call them “spec-inverts”—such that the subjective experience they call “seeing red,” normal people would call “seeing blue,” and what they call “seeing blue,” normal people would call “seeing red,” and likewise for the entire spectrum. When a spec-invert sees a red fire truck, he might say, “I see a red fire truck.” But the qualitative experience he is having is equivalent to the experience a normal person would have seeing a blue fire truck. Of course, the spec-invert who saw a blue fire truck would say, “I see a blue fire truck,” but his experience would be that of a normal person seeing a red one. The important point is that all of the same color discriminations are made, so the difference is undetectable. Asked to separate a pile of red and blue pencils into a red pile here and a blue pile there, the spec-invert will do exactly what the normal person would do. But his experience is different. The trouble for functionalism is that it claims a black box specification of the causal relations among mental states and behavior is sufficient to define a mental state. But on this view, the spec-invert and the normal person have exactly the same mental state, since all of the same causal relations are in place. Yet, by hypothesis, their experiences are different, and this would indicate that there are in fact two different mental states, despite the fact that they function identically. Qualia seem to be a very real part of our mental lives, yet they are absent from functionalism.
Another objection that depends upon our sense that there is something it is like to be in some mental states runs as follows. Imagine the entire nation of China has been converted, as it were, to functionalism. Suppose that the entire population has been organized to behave so as to perfectly imitate the functional organization of a human brain, with all of the input-output relations correctly represented and all of the inner cause-and-effect relations there too. Of course, it could not actually be done, but it is conceivable, since one of the features of black box functionalism is multiple realizability. The problem is that every intuition tells us that the nation of China would not therefore begin to feel like something. The nation of China would not start having subjective qualitative experiences. The claim of black box functionalism is too strong, since it would require that we ascribe a mental life to systems that intuition tells us have none. Now theories can often stretch our intuitions, and sometimes we can give up an intuition or two if a theory is good enough, but there has to be some reflexive equilibrium. Sometimes our intuitions have to rule, especially when they are strong. And the intuition that the nation of China cannot have qualitative mental states is among those strong ones.
A final objection to functionalism will lead us into a discussion of the technically supercharged version of functionalism called computationalism. Black box functionalism allows that two different physical state tokens can be the same mental state type because the different physical states have the same causal role in their respective systems. The problem is that the different physical states are, well, different, so that it is not clear in material terms what it is about the different physical states that could allow them to play the same causal role. Although functionalism as a theory is not committed to materialism—it could be spiritual stuff in the black box—the vast majority of functionalists certainly are committed to materialism. So they need an answer to the question of how two different physical structures can be causally equivalent. The answer comes from computer science.
Computationalism is a functionalist view that can answer the question of how two different physical structures can be causally equivalent. The answer is that two different physical structures can be causally equivalent if they are just two different hardware implementations of the same computer program. If they are causally equivalent, then they are mentally equivalent, and the objection above is answered. The mind can be understood to be a computer program that runs on the brain. Just like your word processing software is not itself a material thing, but always exists in some physical implementation or another, the mind itself is not a material thing, but always exists in some physical implementation, namely, brains.
One might ask: What of the other objections to functionalism? It would seem they still apply, but the research project of computationalism is so overwhelmingly fruitful that theorists have been willing to resist the other objections, or tolerate them, rather than give in and lose what seems to them to be such a promising scientific venture. Here is that venture encapsulated:
Functionalism, by identifying mental states with their roles in the production of behavior, suggests that the explanatory project of the CTC [computational theory of cognition] is to explain behavior—indeed, to explain stimulus-to-response connections (now called I/O behavior)—at a level of abstraction that isn’t neuro-chauvinist by tracking the causal routes through the system via the abstract computational properties of its states.
Among the more interesting things to note is that in this science of the mind we are still talking about the explanation of behavior and not, for example, the qualitative character of mental states for those who have them. Perhaps of greater interest is the fact that, since the mind is understood to be at a level of abstraction above the brain, in something like the way your word processing program is at a level of abstraction above your laptop, it turns out that the brain is not very important in the scientific study of the mind. Of course, brain damage is serious in the same way that spilling coffee on your motherboard is serious: if that is what is running your word processing software, you are out one word processor. That is, until you install the same software on another machine. According to computationalism, minds too could conceivably be installed on machines, and then we would have thinking machines. The prospect is exciting enough that proponents will live with some of the other problems of functionalism in the hope that they too can be solved. Until a better theory comes around, they would say, we should stick with computationalism.
But is computationalism a good theory? For some, no more response to the question of whether or not machines can think need be given than that provided by Peter Geach: “On this matter, I shall be quite brief. Machines manifestly have no life, no senses, no feelings, no purposes except their makers’; there is just no question of ascribing to them the activity of thinking.” Yet a strong case can be made against computationalism that is based not so much on an objection to the idea of computers thinking, but more on an objection to the controversial claim that something is a mind in virtue of being a computer program. These days, behaviorism in philosophy is dead and identity theory has a few proponents, but not many. If anything is close to being the reigning orthodoxy in analytic philosophy of mind, it is computationalism. Yet I think John Searle’s arguments against it are devastating, at least from the materialist point of view. By this, I mean that Searle is committed to the view in at least one of his arguments that the brain is a thinking organ, and this could be wrong if the principle of intellectual operations is immaterial. But as long as he and computationalists share the assumption that there is, in some sense, nothing but particles in fields of force, he has got them where he wants them in his arguments. Perhaps the arguments are currently resisted for the same reason as are the other objections to functionalism that computationalism has not answered.
The two arguments may be divided into what I call the Semantic Argument and the Syntactic argument. The Semantic Argument is the famous Chinese Room. It has the flavor of an absent qualia argument, with which we are already familiar, and the Chinese Room argument is so well-known, that I will treat it fairly briefly, in favor of the Syntactic Argument, which I think is more powerful. To begin, we must know an important fact about how computers operate. Computers operate by the formal manipulation of symbols. That is, computers operate at the level of syntax, not semantics. The only feature of a symbol that a computer can take into account in processing it is its shape, as it were; computers do not operate on the meaning of the symbols they process. In an electronic computer, for example, a certain voltage represents 1 and another voltage 0. But the computer does not operate on the voltages as representing 1’s and 0’s, much less on what the 1’s and 0’s represent. It just operates on the voltages according to the laws of physics.
Now imagine a room in which you sit. You understand no Chinese. Chinese symbols are given to you in the form of questions through a slot in the door, and you return Chinese symbols as answers back through the slot. You do not even know that the symbols are Chinese, and you do not even know that they are questions coming in and answers going out. Yet questions come through in Chinese, and you return answers in Chinese. You can do this because you have been given a comprehensive set of rules telling you what symbols to put out based on what is coming in. Suppose the set of rules, known as the program, is so good that its responses are indistinguishable from those of a native Chinese speaker. Question: Is there any understanding of Chinese going on here? Do you understand Chinese? Does the set of rules? How about you and the rules together? It would seem that the answer to each question is negative. Yet this is problematic for computationalism, because the system seems to meet all the functional requirements for being a Chinese speaker, yet there is no understanding of Chinese happening, the way it does for a speaker. The point is that symbol manipulation alone cannot generate meaning and understanding or any other semantic feature. Yes, many computationalists bite the bullet and, denying intuition, say that the system as a whole—you, the book, the room—really does understand Chinese just like a native speaker. How can one argue about such intuitions?
I think the Syntactic Argument is more powerful than the Semantic Argument, in part because it does not hang on intuitions. The full-blown version of the argument is lengthy, but a summarized version can be just as compelling. A basic distinction in the sciences is between the intrinsic features of a thing, which are independent of us, and the features of a thing that are relative to us, either as observers, users, makers, or the like. That an object is made of clay is an intrinsic property of it. That it is a flower pot is relative to us. The natural sciences tend to deal with intrinsic properties. What is computation? On a narrow construal, where computation is what conscious agents do when they do arithmetic, for example, computation is intrinsic. If you are adding 1 + 1 to get 2, it is intrinsic to you, and it does not matter what an observer thinks about it. But there is a broad construal of computation, thanks to the mathematical and computer sciences, in which literally anything can be a computer based on the fact that we can always come up with some interpretation of its behavior that is meaningful to us. Assign 0 to your closet door when it is closed and 1 when it is open. By opening and closing the door, you can compute 1 and 0. Yes, it is about as primitive a computer as can be, but imagine what you might do with an array of such doors and a good set of instructions. The point is that anything can be a computer.
So what if your laptop is adding 1 and 1? This is not an intrinsic property. It is an observer-relative case, because the computer is intrinsically an electronic circuit whose states transition among voltages. At the level of intrinsic properties, it is nothing more. It is a computer, however, to you, because it was made for you to be treated as a computer, and you do treat it that way, and treating it that way makes sense to you, and so on. Just like the shapes on the computer screen have no intrinsic meaning, but get their meaning as words and sentences from us, so do the state transitions among voltages in the machine get their meaning from us.
The upshot of all this is that the computationalist assertion that the brain is a computer running the mind as a program has no clear sense. Surely what is not meant is that, under the narrow construal of computation, the brain is intrinsically a computer. This is trivially true. Yes, we do arithmetic. So perhaps what is meant is that, under the broad construal of computation, the brain is intrinsically a computer. But this is false, because nothing is intrinsically a computer under the broad construal. Under this construal, whether or not something is a computer is always a matter of interpretation. Finally, if what is meant is that we can assign a computational interpretation to the brain, then this also is trivially true, since we can assign such an interpretation to anything. Whereas the Semantic Argument about the Chinese Room shows that semantics is not intrinsic to syntax, the Syntactic Argument shows that syntax is not intrinsic to physics. Computationalism is untenable because there are no physical facts about a system that make it computational. All of these problems for materialists are enough to make some of them want to stop talking about the mind altogether.
Eliminativism is the view that there are, in fact, no mental states such as those we are accustomed to think we are speaking of when we talk about believing that the earth is round, hoping that the war might end, or fearing the worst. That is, no one believes the earth is round, or hopes war might end, or fears the worst, because there are no such things as beliefs, hopes, fears, or any of the other so-called propositional attitudes. All of the concepts of what eliminativists call belief-desire psychology, or, more often, folk psychology, eventually ought to be abandoned upon the construction and reception of a mature science of the brain. More than one wag has pointed out that if eliminativism is true, then we cannot believe it. But we will not pass over it so quickly.
The first step that eliminativists take, in order to overcome the sense we have upon first encountering their view that it is simply ludicrous, is to cite historical examples from the history of natural science in which the elements of the ontology of an older theory are eliminated outright in favor of the ontology of a new and superior theory. For example, in the eighteenth and nineteenth centuries, it was common to believe that heat is a kind of fluid flowing through and among physical bodies and this fluid was called “caloric.” Along came the theory of kinetic energy, claiming that heat is the clashing of tiny molecules, which made for far more successful predictions of thermal behavior. It was not possible to identify “caloric” and “kinetic energy,” so the notion of a flowing substance was simply eliminated in favor of a kind of motion. Likewise it used to be believed that when a substance is burned it releases “phlogiston.” When it was discovered that in fact burning is not the release of a substance, but the acquisition of a substance—oxygen—from the air, the realization that the theory of “phlogiston” utterly failed to describe the situation accurately led to the abandonment of the theory and its ontology tout court. We can trot out example after example, it is said. What are we to make of celestial spheres and witches? History offers a heap of forlorn items of ontological furniture that at one time we were so sure were there. The concepts of folk psychology—belief, desire, sensation, pain, hope, joy, fear, and all the rest—await a similar fate.
The biggest difference, then, between eliminativism and the views outlined above is that there is a claim here that there will not be a smooth intertheoretic reduction—even one that is merely species-specific—of the concepts of folk psychology to the concepts of a mature neuroscience. Behaviorism, identity theory, and functionalism never said that we do not have mental states like beliefs and desires. What they said, against the background of substance dualism, was that these mental states are not what we thought they were. The conviction of eliminativism, on the other hand, is that talk of such things as beliefs and desires must be replaced by something new, because such talk is hopelessly muddled and confused, representing a primitive view of the internal activities of human beings meant to explain their outward behavior.
There are basically three arguments that eliminativists put forth in favor of their view. One that we shall ignore is an argument that attempts to find an advantage for eliminativism as compared to identity and functionalist theories. This is a family spat among materialists that need not concern us. So the first we consider is from the poverty of explanation that is supposed to characterize folk psychology. There are many examples, but we may be asked to think about such common and fundamental occurrences in our mental lives as the following, about which folk psychology can offer no account: sleep, learning, intelligence, memory, and mental illness. These are central things about us that remain utterly mysterious from the point of view of folk psychology. Not only is folk psychology unable to give any account of these normal happenings, it is even worse at explaining some of the astonishing results of brain damage, the manifestation of cognitive and behavioral difficulties that occur when the brain suffers trauma or pathology.
The second argument is an attempt to draw a lesson from the history of ideas. We are asked to inductively reason to a particular conclusion from premises based on examples of conceptual abandonment like those provided above. We know that what was commonly believed about motion in what we might call folk physics, say, two thousand years ago, was deeply flawed. Folk astronomy, hardly distinguishable from astrology, was full of superstition and falsehood. We have in the past profoundly misunderstood everything from fire to life. It seems that just about every folk theory there has been has been conceptually exploded by the development of the natural sciences. One of the few remaining such theories is our belief-desire psychology. But if all of our other folk approaches to explanation are known to have been so far off the mark as to have been completely disposable, and what they were attempting to understand cannot match the complexity of the human mind, then we should be prepared to abandon folk psychology in favor of a much more progressive and sophisticated account of the mind based in neuroscience. Folk psychology has not survived because it is basically correct, but for the reason that, no matter how feeble it is, it has been difficult to replace it because the phenomena in question are so exceedingly difficult to describe and explain in the first place.
What are we to make of the barrage of historical examples and these two arguments? The list of historical cases is meant to browbeat us into submission. They are ultimately tied into the second argument, which John Searle calls the “heroic-age-of-science maneuver.” Both arguments depend upon the assumption that folk psychology is a kind of theory in which we postulate entities such as beliefs and desires in order to explain what is going on in and around us. As such, folk psychology is in competition with other theories that help us to understand our behavior. Corollary to this assumption is the materialist conviction that, like those of any higher level theory, the concepts of folk psychology ought to be reducible to more basic sciences and, ultimately, physics; if they cannot be so reduced, they must be abandoned. The first argument says that we should abandon folk psychology because as a theory it is explanatorily impoverished and remarkably inadequate relative to neuroscience. The second argument says that we should completely reject folk psychology because it is just one more in a long series of folk theories that we know to have been abandoned because their concepts were so far off with respect to reality that intertheoretic reduction to progressive scientific concepts was impossible.
The problem with eliminativism is its characterization of folk psychology and the central role it gives to reduction. Folk psychology is not an empirical theory, a set of propositions about human behavior, subject to scientific methods of confirmation and disproof. Folk psychology is best thought of as a capacity. It is how we understand and respond to everything from facial expressions and bodily movements to linguistic behavior. It is better thought of as know-how, not theory. Even if we could somehow express the practical skills in theoretical principles, we would likely find that the eliminativist is just wrong, because folk psychology would have to turn out to be true, at least as far as it goes. Yes, the ancients may have been wrong in some ways about fire, motion, and the starry skies, but they certainly knew not to put their hands in the flame, what would happen if they jumped off a cliff, and how to map the regular patterns of the night sky and navigate by them. In other words, they got the very important things right, and we know this to be true because we are still here.
It is also not true that folk psychological notions like belief and desire are entities that we postulate in competition with the concepts of scientific theories:
It is a hot day and you are driving a pickup truck in the desert outside of Phoenix. No air conditioning. You can’t remember when you were so thirsty, and you want a cold beer so bad you could scream. Now where is the “postulation” of a desire? Conscious desires are experienced. They are no more postulated than conscious pains.
In particular, we do not postulate beliefs and desires as a means of accounting for human behavior, the way that scientific psychologies might postulate their theoretical entities to do so. Beliefs and desires no doubt cause behaviors, but more often they do not issue in actions:
For example, I believe that the sun is 94 million miles away, and I would like to be a billionaire. Which of my actions do this belief and this desire explain? That if I want to buy a ticket to the sun I will be sure to get a 94-million-mile ticket? That the next time somebody gives me a billion, I won’t refuse?
Finally, the eliminativist supposition that folk psychological concepts must be reducible to more basic scientific concepts or be expelled from thought is unfounded. The truth is that the real entities we encounter in everyday life do not undergo the kind of intertheoretic reduction that eliminativists demand and they are no less real for that. The books on your shelf, your bedroom, the last chess game you played, and last year’s Christmas party are all quite real despite the fact that you would find it impossible to give a smooth reduction of them to some fundamental theory. The reducibility of an entity to some more basic, comprehensive, or explanatorily superior taxonomic system is irrelevant to the question of its existence. Moreover, even if beliefs and desires were not like the entities we encounter in everyday life, but really were theoretical entities, we still should not expect any kind of reduction. In economics, we readily speak of interest rates, marginal costs, supply, and demand with no requirement or expectation that they must be reducible, even in principle, to psychology, or biology, or physics.
Materialism is in real trouble. The foremost materialist approaches to the philosophy of mind—behaviorism, identity theory, functionalism, computationalism, and eliminativism—all seem to fail in their efforts to reduce the mental to the physical. We cannot of course conclude from this failure alone that all materialist efforts must fail. But we can certainly feel enough frustration to look for reasonable alternatives. The first step in this case, then, would be to seek out positive reasons to believe that there is perhaps an immaterial aspect to the mind. Any arguments marshaled to make the case for the immateriality of the mind will have to show at least the potential for true engagement in the current conversation. For one thing, this means substance dualism is out, so none of our arguments ought to come from that perspective. The best candidates for proofs of immateriality will be examined soon in the following chapters. However, we cannot yet move on without turning to one more materialist view, that of John Searle.
Searle is a materialist in the sense that he believes that there is one world, constituted by particles in fields of force, and there are no additional mysterious substances or properties. Searle is emphatically not a materialist in the sense in which that means in philosophy of mind one who seeks to reduce the mental to the physical. He does not seek to do this and he is dedicated to the claim that the mental is, at least in one sense, not reducible to the physical. On the other hand, he denies being a property dualist. That is, he does not think that there are mental properties distinct from the physical such that after filling up the universe with all physical objects and their physical properties, God would then have to make an extra effort to add further mental properties in order to complete things. This is a playful version of how Searle himself characterizes property dualism, and he vehemently denies being an adherent of this view.
One of the qualities that makes Searle so intriguing and his work so attractive at times is his commonsense approach. This has been revealed already in the objections to the various systems outlined above that come from him. Unlike most analytic philosophers, he has favored ontology over epistemology. It is hard not to like the work of a thinker whose views have been so accurately described in this way:
There is no need for endless rallies around the epistemological flag in order to say certain things about what is out there in the world. . . . Our ordinary powers are good enough to tell us about most of what we know. To be sure, these powers can be fooled in certain situations. But when they lead us to believe that stars, mountains, rain, trees, grass, deer, cats, dogs, and ants and, even, consciousness are real we should be reluctant to doubt these beliefs. Instead of doubting the existence of all these things we should be engaging in processes of thinking that gain us understanding of their nature and structure.
“Biological naturalism” is the name John Searle has given to his views about the nature of the mind. In his characteristically sharp and clear prose, Searle claims:
The famous mind-body problem, the source of so much controversy over the past two millennia, has a simple solution. This solution has been available to any educated person since serious work began on the brain nearly a century ago, and, in a sense, we all know it to be true. Here it is: Mental phenomena are caused by neurophysiological processes in the brain and are themselves features of the
brain. . . . Mental events and processes are as much part of our biological natural history as digestion, mitosis, meiosis, or enzyme secretion.
His opinion is that the study of mind is the study of consciousness in much the same sense that biology is the study of life. That this puts him outside the mainstream should be apparent, based on the fact that all of the previous views considered have regarded the proper study of the mind to be the science of behavior. Searle’s commitments may be summed up nicely in four basic propositions.
(1) Consciousness is real.
(2) All conscious states are caused by neurobiological states; the slogan is: Brains cause minds.
(3) Minds are realized as higher level brain processes.
(4) Conscious states function causally.
Point (1) is clear enough: Searle is against the various forms of materialism because they deny the presence of irreducible mental phenomena in the world. As mentioned in the section above on substance dualism, he believes materialists—whether they know it or not— accept the traditional Cartesian categories and the accompanying vocabulary with its implications. That is, he thinks they are inextricably caught up in the messy web of ideas historically spun from the erroneous conviction that the mental and the physical are distinct metaphysical realms.
Point (2) requires some explanation. It is important to keep in mind that Searle is always at pains to avoid the dualism inherent in our talk about the mental and the physical. He does not mean to say that there are two different things, brain processes as causes and conscious mental states as effects. To view it this way is to have succumbed to a mistaken conception of causation that supposes the causal relation is always one in which discrete events are ordered sequentially in time. To be sure, there is such causation. The pounding of the hammer causes the nail to sink into the wood. However, a more full conception of causation, and the one applicable here, comes about when we reflect upon our common experience. Gravity causes the table to exert pressure on the floor beneath it, but gravity is not an event. The solidity of the table is caused by the behavior of the molecules that compose the table, but the solidity is not an event that results from the molecular behavior, it is just a feature of the table. Hence, to say that the brain causes conscious mental states is to say that conscious states are features of the brain. This leads to point (3).
Point (3) answers the question raised by point (2); namely, what kind of feature of the brain is consciousness? The answer is that consciousness is a higher level brain process. This is to be understood in much the same way we understand, say, solidity as a higher level feature of a table. There is no difficulty in supposing that the higher level feature of solidity is caused by the lower level behavior of the molecules that make up the table. In the broad sense of causation explained above, the lattice structure of the molecular arrangement at the lower level causes the higher level feature of solidity. We could identify the lower level lattice structure with the higher level solidity in the following sense. It is characteristic of science that we take an expression that is first defined in terms of the higher level sensible features of an object and redefine it in terms of the lower level structures that cause the sensible features. Solidity first means to us that the table is rigid and resists pressure. We note that the solidity of the table means that it can support our dinner plates and resist penetration by our forks and knives. Making some scientific progress in our knowledge of the table, we come to know the molecular structures that give the table the features we initially observed and we now call this solidity too. What is important is that we do not then say that solidity no longer means rigidity, resistance, or relative impenetrability. What we now have are options. We can talk about solidity as a lower level behavior of the table and as a higher level feature of it. Similarly, we can talk about consciousness as a lower level behavior of the brain and as a higher level feature of it. The big difference at this point is that whereas we have a good understanding of how the lattice arrangement of molecules in a table causes rigidity, resistance, and relative impenetrability, we have almost no understanding of how the molecular behavior of the brain causes consciousness. But this is not a philosophical problem, it is a scientific one.
Finally, point (4) expresses Searle’s commitment against various forms of dualism that would deny the causal powers of conscious mental states. Conscious mental states cause other conscious mental states and they cause our behavior. They are not epiphenomenal nor do they constitute a separate chain of causal events in a mental realm distinct from the chain of causal events in the physical world. Inasmuch as we can understand how the brain’s lower level molecular behavior would be involved in the causal nexus of the physical world, we can understand how the higher level feature of conscious mental states caused by that lower level behavior—in the sense of causation described above—would be involved in the same causal nexus. This, by the way, is Searle’s solution to the notorious mind-body problem.
It may not be quite clear yet how Searle can see himself as belonging to neither the materialist nor the dualist party in philosophy of mind. As has been mentioned, he says he accepts the obvious facts of physics—for example, that the world is made up entirely of particles in fields of force—along with the obvious facts of our experience—for example, that we have conscious mental states with irreducible phenomenological properties. Sometimes it sounds as if he does think we can reduce the mental to the physical, since he talks about higher level mental features as caused by lower level brain processes and this would seem to open the way for reduction. This would make him a materialist. On the other hand, if he does not reduce mental features, we may ask how he is not a property dualist, since property dualism is the view that although there are only physical objects in the world, these objects may have both physical and mental properties, and both physical and mental properties are basic properties that are neither conceptually reducible to each other nor to anything else more basic.
The solution is supposed to go like this. Conscious mental states are causally reducible, but not ontologically reducible. This explains why it sometimes sounds like Searle is a reductive materialist. Conscious states are causally reducible because they are just higher level features of the brain caused by lower level brain processes, just like the solidity of a table is a feature that can be causally reduced to an arrangement of molecules, because the arrangement of molecules causes the solidity. Now we can ontologically reduce solidity, and say that solidity is just the arrangement of molecules. We thereby give up the features of rigidity, relative impenetrability, and so on. We have reduced them to the arrangement of molecules and they are lost. But, Searle says, maybe we would want to do that for the purposes of fitting solidity into some broad theory about reality. We do this with colors when we describe a color as a certain wavelength of light to fit it into physics, even though we are then dropping the look of the color in the definition. We think this is okay, because the appearance of the color is not relevant to us in the study of physics. It may be elsewhere, but not in physics.
Here is the difference with conscious mental states: they have first-person ontology. By this, Searle means that conscious mental states only exist when experienced by a human or animal subject. We do not do an ontological reduction of conscious mental states because, unlike the study of physics, wherein how things appear to us does not matter, in our study of the mind, the appearances are essential. The fact that being in a certain mental state has a certain feel to it, a certain way that it appears to us to be in that state, and that that certain feel is what makes the state what it is, is not a fact we can reduce without eliminating the subject of our study. So conscious states are ontologically irreducible, and this is what makes Searle seem like a property dualist.
Unlike the previous sections, this one will not conclude with a lengthy critique of the point of view presented. I have not yet settled on what I think is wrong about Searle’s views, but the troubles seem to lie in his claims about reducibility. We ontologically reduce solidity and color and such by stripping off the way that they appear to us, that is, by ignoring the features they have that arise from their interaction with us as conscious minds. Searle says that we cannot do this with consciousness itself, because the appearances are everything. This seems to be true. But if every causal reduction can become an ontological reduction, so to speak, by stripping off the features that arise from consciousness, except of course the causal reduction of consciousness itself, then it looks as if the norm is that causal reduction is always ontological reduction, or at least potentially so, except for the strange case of consciousness, which is not subject to ontological reduction and is the one element that fouls up the ontological reduction of physical phenomena until we agree to strip it away. If I cannot do an ontological reduction of consciousness, then why should I believe that consciousness has been causally reduced in the first place? Every other causal reduction can lead to ontological reduction as long as we are willing to bracket those features that are caused by consciousness. If everything is just particles in fields of force, what makes consciousness the one great exception? Searle says that it just is. I suspect he is genuinely concerned that any other suggestion would be problematic in terms of compatibility with the natural sciences. But I also think, given the tradition from which he comes, that there is a little prejudice in favor of the physical.
At the beginning of this chapter, I said that modern thought about the mind tends in three directions: substance dualism, property dualism, and materialism. Perhaps there is a sense in which it would be better to say here at the end that modern thought about the mind has for the most part really proceeded in one direction: the direction set by substance dualism. John Searle is a wily exception to the rule. We will now move on to consider our questions from the interlude: Are there any positive reasons to believe that there is perhaps an immaterial aspect to the mind? Do they avoid attachments to the tradition of substance dualism? And, finally, do they show any potential for real engagement in modern contexts?
Consciousness has been the hot topic in the philosophy of mind for the last ten or fifteen years. Prior to that time, philosophy and psychology had focused primarily on the study of behavior as the authentic study of the mind. Enjoying his new-found freedom to discuss consciousness in the last decade of the twentieth century, one prominent thinker joked with excitement, “The Nineties are to consciousness what the Sixties were to sex.” The publication in 1996 of David J. Chalmers’ Conscious Mind is a watershed in the recent history of thought about the nature of the mental in Anglo-American analytic philosophy. Chalmers succeeded in doing what many thinkers in the analytic school had thought would be impossible: he made dualism a respectable subject for consideration within the tradition and has garnered much serious support. Briefly put, what Chalmers proposes is not a Cartesian dualism of substances, res cogitans and res extensa, but a dualism of properties. The idea is that although there are only physical objects in the world, these objects may have both physical and nonphysical, or mental, properties. Both physical and mental properties are basic properties that are neither conceptually reducible to each other nor to anything else more basic. It is difficult to categorize this view. On the one hand, property dualism may be regarded as a brand of materialism, since it proposes that the physical object (or substance) is the only kind there is. On the other hand, it may be regarded as a brand of antimaterialism, since it proposes irreducibly mental properties. Taxonomic issues aside, here is the connection to consciousness: one underlying reason why Chalmers and those in his camp hold to this view is that they believe that all concepts of physical properties are ultimately definable in functional terms in the scientific theories in which they occur. Concepts of conscious mental states, however, precisely because of the character of consciousness—precisely because it is like something to be in such states—are not amenable to functional definition. Since all concepts of physical properties are ultimately definable in functional terms, and concepts of conscious mental states are not, such states must have nonphysical properties. This leaves us with a gap in our explanations of why the world is the way it is. We cannot explain consciousness.
Chalmers’ main argument on behalf of nonphysical properties is that since it is possible to conceive of a world of beings physically identical to us, but without any corresponding conscious mental states, conscious mental states are not reducible to the physical. In his own words, “The argument is complex, but the basic idea is simple: the physical structure of the world—the exact distribution of particles, fields, and forces in spacetime—is logically consistent with the absence of consciousness, so the presence of consciousness is a further fact about our world;” that is, it is not a physical fact. Consciousness is a nonphysical feature of the world. There is an explanatory gap because there is a real gap in the world and that gap is between physical and mental properties.
When I began the present work, I anticipated a certain measure of agreement on my part with the arguments in favor of property dualism, since I believed that:
(1) there is an explanatory gap with respect to conscious mental states;
(2) the explanatory gap must point to a real gap in the world;
(3) reductive materialism—roughly, the idea that all phenomena can be whittled down to basic physical properties—cannot admit such a gap;
(4) reductive materialism is false, for these reasons among others.
Thinking that I would be convinced in the direction of property dualism, I then planned to make use of the work of Gordon Barnes, who argues that anyone who is convinced of the truth of property dualism ought to move to a substance hylomorphism, that is, a Thomistic-Aristotelian conception of the mind. He does this by arguing that the only way a property dualist can avoid the charge of epiphenomenalism is to deny that the human body is strictly identical with the sum of its microphysical parts, in something like the way that a statue is not identical to the lump of clay out of which it is made, although both occupy the same space at the same time. Further, Barnes argues, the only way to sustain such a view about the human body is some kind of hylomorphism. Such an argument for a Thomistic-Aristotelian conception of the mind might have had a chance of being heard even in analytic circles in the long run, especially if one could convincingly demonstrate that, whatever else it may be, the Thomistic conception of the mind is not substance dualism.
However, this chapter is dedicated to demonstrating that the explanatory gap need not point to a real gap in the world. That is, (2) above is false. As a result, I have abandoned the opinion that there is a conclusive argument from the explanatory gap to antimaterialist conclusions that might support a move to a Thomistic-Aristotelian conception of the mind. Positively put, there are good reasons to believe that the existence of an explanatory gap is compatible with materialism. This claim is based upon the work of Joseph Levine.
Levine’s contention is that in our thinking about the mind, current arguments for an explanatory gap do not ultimately “demonstrate a gap in nature, but a gap in our understanding of nature.” The purpose of this chapter, then, is to provide a brief exposition of the most recent efforts of Levine—his canonical statements, as it were—concerning conceivability, identity, and the explanatory gap, particularly in his book Purple Haze: The Puzzle of Consciousness, but also in other, shorter works. The enterprise will be (1) to discuss conceivability and Levine’s take on it, both with respect to antimaterialist arguments from conceivability to possibility, and to his own claim that conceivability considerations show we cannot explain our mental life in terms of the physical world; (2) to lay out the argument for this explanatory gap; (3) to examine a provisional account of how the gap occurs and propose a revised account based on considerations of the nature of identity; (4) to deploy a new notion of identity to account for the gap; and (5) to see how antimaterialists might exploit this new notion and how Levine proposes to rebut them.
In the battle between materialists and antimaterialists, one of the weapons marshaled by antimaterialists and used to great effect by them in the current, ongoing debate in philosophy of mind about the nature of consciousness has been the so-called conceivability argument. Although it is prominent in recent work, conceivability has a long philosophical history, respectable or otherwise depending upon one’s point of view. Descartes of course famously argued in the Sixth Meditation of his Meditations on First Philosophy that from the conceivability of existence as a mind without a body, he could conclude to a substantial distinction in reality between the mental and the physical. Making a point still relevant today about the relationship between conceivability and possibility in his Treatise, Hume asserts as an established metaphysical principle that possibility is always included in conceivability: “Whatever the mind clearly conceives includes the idea of possible existence, or in other words…nothing we imagine is absolutely impossible.” To return to the present, perhaps the briefest expression of the premise of the conceivability argument with respect to conscious mental states belongs to Levine: “When I conceive of the mental, it seems utterly unlike the physical.” For the antimaterialist, this is supposed to lead to the conclusion that the mental and the physical are two separate and distinct ontological realms.
Contemporary efforts to throw light upon the character of mind have led to book-length treatments of the conceivability argument. However its major proponents have also been able to sum it up handily. For example, David Chalmers expresses the argument this way:
A somewhat more general and precise version of the argument appeals to P, the conjunction of all microphysical truths about the universe, and Q, an arbitrary phenomenal truth about the universe.
(1) It is conceivable that P & ¬Q.
(2) If it is conceivable that P & ¬Q, it is metaphysically possible that P & ¬Q.
(3) If it is metaphysically possible that P & ¬Q, then materialism is false.
(4) Materialism is false.
One standard materialist response to such an argument is to challenge the move from conceivability to possibility. May we validly infer from mind-dependent facts in the epistemic sphere of the conceivable to mind-independent facts in the metaphysical sphere of the possible?
In Purple Haze, Levine argues against the likes of Chalmers that whereas it is true that phenomenal facts cannot be derived a priori from physical facts, i.e., that it is conceptually possible for the physical as we know it to obtain without the phenomenal, it does not follow that phenomenal facts are not realized by physical facts, i.e., that materialism is false. Levine argues according to the following principle: “The conceivability of a state of affairs S constitutes evidence for the possibility of S only if the possibility of S is the best explanation of the conceivability of S.” That is, if S is conceivable, then one explanation for its conceivability is its possibility. However, the conceivability of S is evidence of S’s possibility only so long as there is no other explanation of the conceivability of S that competes favorably against the explanation from possibility.
Against Chalmers’ argument, Levine proposes an explanation for the conceivability of P & ¬Q that makes no appeal to possibility and thus undercuts the inference from conceivability to possibility that leads to the antimaterialist conclusion. The suggestion is that when we represent a situation to ourselves, the logical form of that representation may disallow a formally inconsistent representation of the same situation in thought even though in fact there is one to be had. Suppose that, in fact, it is impossible that the physical as we know it should obtain without the mental obtaining also (and the reverse is true). We might still be able to conceive of the absence of one or the other, mental or physical, since we could be representing our own conscious states to ourselves without grasping the necessary and sufficient conditions for being such states, that is, for being the referents of the representations in question. Were our representations to include a grasp of the conditions for being their referents, the conception of the physical and mental as separate and distinct in a Cartesian sense would be impossible, since the representation would show the physical and mental to be ineluctably bound up with one another, as initially supposed. But as it is, even if there is a formally inconsistent representation of the situation concerning our conscious states, we do not think it, and not because of any possibility in the world, but because our representations of our conscious states “do not wear their satisfaction-conditions on their sleeves.” So on the one hand, Levine commits himself to a materialist point of view, contending that a mere consideration of what is conceptually possible cannot ground a dualistic distinction between the mind and the body, or demonstrate that mental properties can never be reduced to physical properties. On the other hand, he insists that conceivability considerations indeed show that we cannot explain our mental life in terms of the physical world.
The argument for this inability to explain our mental life runs as follows. It does seem to be conceivable that there could be a creature which exists just like us in all physical aspects, but which creature does not share with us the experience of there being something it is like to be the sort of living things we are. Yet if we really understood what it is about our physical states that gives rise to there being something it is like for us to be in those states, then it would simply not be conceivable that a creature such as we just imagined could exist. As Levine puts it:
Suppose creature X satisfies physical description P. I understand—from my physical theory of consciousness—what it is about instantiating P that is responsible for its being a conscious experience. So how could X occupy a state with those very features and yet not be having a conscious experience?
It is conceivable that a creature such as we imagined could exist. Therefore, we do not really understand what it is about our physical states that gives rise to there being something it is like for us to be in those states. In other words, we lack an explanation for how we as physical creatures can have the mental lives that we do, and thus we must recognize, in Levine’s celebrated phrase, an explanatory gap in our knowledge of ourselves. While materialism may be true, and Levine thinks there are excellent reasons for thinking that it is, “there is still an important sense in which we can’t really understand how it could be true.”
In order to bring about a feel for the full force of the argument for an explanatory gap, Levine contrasts instances of explaining various conscious states, such as the way a pain feels, or the way a red object looks, in physical terms with instances of explaining other macro-level phenomena in terms of underlying microphysical processes. In particular, he compares the explanation of the boiling point of water at sea level with a putative explanation for the reddish character of a visual sensation (caused by a red diskette case). Consider the following sketches of two explanations.
ESI: Boiling Point of Water
(1) H2O molecules exert vapor pressure P at kinetic energy E.
(2) At sea level exerting vapor pressure P causes molecules to rapidly escape into air.
(3) Rapidly escaping into air is boiling.
(4) 212°F is kinetic energy E.
(5) Water is H2O.
(6) Water boils at 212°F at sea level.
ESII: Presence of Reddish Qualia
(7) S occupies brain state B.
(8) To occupy brain state B is to experience a reddish quale (state R).
(9) S is experiencing a reddish quale.
Levine recognizes that it is controversial to characterize scientific explanation as a deductive derivation of an explanandum from the explanans, but he claims that the crucial issues at stake here do not depend upon his particular take on explanation, and delving into his thoughts on explanation in general is beyond the scope of this work. What he wants to advocate is that despite superficial similarities, including the use of key “bridge” premises [(5) in ESI and (8) in ESII] that identify the phenomenon to be explained with phenomena describable in a vocabulary for the micro-level, there is a difference between the two sketches. The difference is supposed to be that ESI seems to be a satisfying explanation whereas ESII seems to suffer from an explanatory gap. The bridge premises (5) and (8) are taken to be the source of the asymmetry.
One possible means to account for a distinction between premise (5) and premise (8) is that (5) “Water is H2O” can be derived from a set of statements that are either analytic, that is, knowable on the basis of conceptual competency, or are descriptions of underlying microphysical phenomena. Levine provisionally considers this account. Premise (8) “To occupy brain state B is to experience a reddish quale (state R)” cannot be derived from such statements. So the difference between the two is that in ESI, the case of water, the bridge premise—the identity—is itself susceptible of explanation, whereas in ESII, the case of qualia, the identity is not susceptible of explanation. What is the explanation for (5) “Water is H2O”? There is an expansion of the term ‘water,’ a conceptual analysis that gives the conditions for being water. In short, water is the stuff that manifests the “watery” properties, like filling lakes and falling as rain from the sky, being liquid and quenching thirst, and since H2O manifests the “watery” properties, then water is H2O. This works as an explanation, Levine supposes, because it is an analytic truth that water is “watery,” so this requires no further explanation itself. Moreover, “watery” is ultimately definable in what Levine calls “topic-neutral” terms, a topic-neutral expression being “one that does not contain any non-logical vocabulary that is not already included in the vocabulary of the theory that’s doing the explaining.” This means that ultimately everything is given in terms of microphysical processes.
Applying the same process to ESII, Levine describes the explanation for (8) “To occupy brain state B is to experience a reddish quale (state R).” Qualitative state R is the state that plays causal role C, and since brain state B plays causal role C, then brain state B is qualitative state R. The problem, Levine thinks, is that while experiences of a certain reddish character may play a causal role, it appears not to be a conceptual truth that they do play such a role. The justification for this claim is supposed to come from the conceivability argument. It seems conceivable that we could be having any given conscious experience without it playing the typical causal role for that state. Recall that it does not matter that it might not really be possible that we are having such an experience without it playing its typical causal role. The mere fact that it seems conceivable is taken to show that the assertion is not analytic and thus remains in need of explanation. There is an explanatory gap in ESII that does not exist in ESI.
At this point, Levine considers an objection to his provisional analysis. The first line of attack is that statements such as ‘water is “watery”’ are not in fact analytic or reducible to topic-neutral terms. Should one protest that this ought to cause an explanatory gap in ESI since (5) “Water is H2O” remains unexplained, but clearly there is no such gap, the second line is to argue that (5) does not require an explanation and the assumption that it does is incorrect. Hearkening back to Quine, the first line of the attack is based on the reputed fact that, with the exception of a few cases like ‘bachelor’ or mathematical concepts, there are no convincing examples of conceptual analysis to be found. Is it really the case that water filling lakes and falling as rain from the sky is analytic? If not, are we just waiting for the correct analysis to come around? The burden would seem to be on the proponent of analyticity to show that we have reason to believe that the correct conceptual analysis is around the corner.
Perhaps there is a reason to believe such an analysis is waiting. Because without such an analysis for terms like ‘water,’ there is no explaining an identity like “Water is H2O.” This is where the objector replies with the second line of attack: such identities do not require an explanation. It is simply a brute fact that something is itself and we must accept it. It could be that the question is, “How does H2O play the role that water plays?” That is, we might ask how H2O is liquid, transparent, and thirst-quenching, for example. Alternatively, we might be asking why we should believe that water is H2O. In any case, these questions make sense and they have an answer in chemistry. “It’s after all is said and done, the chemical explanations are all in place, and I still persist in my wonderment, that one is absolutely puzzled as to what substantive content there could be to my wondering.”
Having accepted this reasoning, Levine concludes that the absence of a gap in ESI has nothing to do with having the right analysis of the term ‘water,’ and thus nothing to do with having an explanation for the bridge premise—the identity statement “Water is H2O.” There is no gap in ESI because identities do not typically require explanations. But if ESI does not require analytic statements in order to avoid an explanatory gap, then the lack of analytic truth in ESII cannot be a reason for there being an explanatory gap in that instance. In fact, if “Water is H2O” requires no explanation, then neither does “To occupy brain state B is to experience a reddish quale (state R)” and there is no explanatory gap between the mental and the physical at all. Yet the entire thrust of Levine’s work is that there is such a gap. How can this be?
In response to the argument above, Levine asserts the existence of “gappy identities.” The objection to the provisional analysis was based on the apparent truth of the claim that identities do not themselves require explanation. Identity statements can be used as premises in explanatory arguments without bringing with them a new demand for explanation and potentially causing an explanatory gap. Levine concedes that this seems to work for ESI, involving water, but he does not accept that the same works for ESII. There is, he thinks, still room in ESII for a reasonable request for further explanation and he wants to say that this is based on a difference between the identity claims in the two cases. An identity claim that “admits of an intelligible request for explanation” is “gappy” and “nongappy” otherwise.
Levine thinks that “Water is H2O” is a nongappy identity, whereas “To occupy brain state B is to experience a reddish quale (state R)” is a gappy identity. He illustrates the distinction by consideration of three cases: one involving indexicals, one involving demonstratives, and one involving natural kinds. First, consider indexicals. It never logically follows from any physical description of what is happening to a certain body at a certain time and place—however complete the description—that it is happening to me here now. I cannot derive “My hand is cut now” from “Such and such a body encountered a knife at time t” without bridges like “Such and such a body is mine” and “Now is soon after time t.” No one suggests that this inability to derive “My hand is cut now” from non-indexical statements shows that being mine and being now are metaphysically irreducible. More importantly, upon reception of the bridge statements to the effect that the body is mine and time t is shortly before now, does it make sense, Levine asks, to inquire, “How could that be my body?” or “How could now be after t?” I might think that the body in the non-indexical statement has different properties from mine and then the questions would make sense. But the notion of “mineness” in its own right seems to be what Levine calls “thin,” and thus “to wonder how the body referred to in the explanans could have it (i.e., being me, or mine) doesn’t seem to have any cognitive substance.”
Similarly, Levine asks us to imagine pointing blindly in front of ourselves and saying, “I wonder what that is.” We know nothing more substantive than that what we are pointing at is an object in space. Opening our eyes, we see what it is we are pointing at—say, as in Levine’s example, it turns out to be a red diskette case. Again, there seems to be no cognitive substance to the question, “How could my red diskette case be that?” “Once I’ve determined that it’s the red diskette case that occupies the relevant contextual niche, there’s just nothing more to wonder about.” As in the case of indexicals, we cannot derive “That = [your name]’s red diskette case” from statements containing only non-demonstrative terms. And also as in the case of indexicals, this inability to accomplish such a derivation is not taken to show that there is any sense in continuing to wonder how that could be the red diskette case.
Finally, consider natural kinds. Since it is fresh on our minds, we will think of water and H2O. In deciding above that ‘water is “watery”’ is not in fact analytic or reducible to topic-neutral terms, the implication was that we cannot derive statements containing the term ‘water’ solely from statements that do not contain that term. “Yet once we discover that H2O is indeed the substance that lies at the other end of the contextual reference-determining relation from ‘water,’ it does seem that there is little sense to be made of my wondering how H2O could be water.” Recall, we are not talking about a request for justification or an explanation of how H2O is liquid or thirst-quenching, as water is. These questions make sense and the underlying chemistry provides answers to them. But once the chemistry is understood, to persist in wondering how H2O could be water seems to be without any substantive content.
Levine claims that “in stark contrast to these three examples stands the case of qualia.” Let us say we are informed that “To occupy brain state B is to experience a reddish quale (state R).” We understand the neurophysiological facts just as well as we understand the chemical facts about water. Then experiencing a reddish quale and pointing to it, so to speak, we ask, “How could occupying brain state B be that?” Even if we accept the identity claim, we can see that there is substantive content to the wonderment, especially in comparison to the cases of indexicals, demonstratives, and natural kinds above. Going back to ESI and ESII, we accept the identity of water and H2O in ESI because of its explanatory power. The identity itself requires no explanation and no stone is left unturned—the identity is nongappy. However, this is not the case in ESII. There is still room for puzzlement. The claim that “To occupy brain state B is to experience a reddish quale (state R)” is a gappy identity because, even if we accept it, it is intelligible to request further explanation for it. Explanations that rely essentially on gappy identities suffer from an explanatory gap.
Levine’s claim is epistemological. Mental properties might be ontologically reducible to physical properties, but mental properties cannot be explained in terms of physical properties. Nevertheless, the question arises whether the antimaterialist can make a case for himself with the notion of a gappy identity. Recall that nongappy identities require no explanation and leave no room for a reasonable demand for one. By contrast, gappy identities do leave space for an intelligible request: “Yes, X = Y, but how can X be Y?” Given the plausibility of the claim that pure identities require no explanation and that such nongappy identities are pervasive—the study of the mind apparently being uniquely exceptional—then why allow the exception at all? That is, the antimaterialist can argue that all true identities are nongappy. Gappy identities, on the other hand, reveal that “we really have in mind two distinct properties that are alleged to be instantiated in the same thing.” Our request for further explanation in the face of a gappy identity is a request for an explanation for the co-instantiation of two distinct properties, which must exist if this interpretation of gappy identities is correct. This means that the identity “To occupy brain state B is to experience a reddish quale (state R),” if it is gappy—and the antimaterialist and materialist agree that it is—says something about one property ‘to occupy brain state B’ and another distinct property ‘to experience a reddish quale.’ This in turn means that being a reddish quale is not reducible to a neurophysiological property. The antimaterialist derives a metaphysical conclusion from an epistemological premise about what an intelligible object of explanation is.
The original materialist objection to such a move on the part of the antimaterialist is that one cannot infer from conceivability to possibility. The nature of all of reality—including our minds—is independent of our cognitive access to it. How does Levine apply this objection to the antimaterialist interpretation of gappy identities? The problem, he says, is that gappy identities are themselves a puzzle requiring an explanation that is not easy to come by from the materialist perspective. Still we must come to appreciate that there is a metaphysical side to explanation as well as an epistemological one. “When I say that phenomenon A explains phenomenon B, one thing I mean is that A’s obtaining is responsible for B’s obtaining. This is a metaphysical notion. I also mean that I can understand why B obtains, B’s obtaining becomes intelligible to me, once I know that A obtains (together with B’s connection to A). This is an epistemological notion.” The antimaterialist argument “seems to be based on a kind of Cartesian model of access to the facts, one that blurs the line between epistemology and metaphysics.”
Examining a nongappy identity from the metaphysical perspective, the claim is that nothing is responsible for the identity other than the identity itself. The identity is a brute fact. Examining a nongappy identity from the epistemological perspective, the claim is that once we have answered all questions about justification for belief in the identity and how one of the relata plays the role of the other, there is no more to explain. Looking at a gappy identity, the materialist says that, from the metaphysical perspective, the identity is a brute fact, that is, there is nothing beyond the identity that makes it obtain. From the epistemological perspective, we still conceive of the two sides of a gappy identity as distinct properties, or as one thing manifesting independent properties. In thinking about the mind, we cannot see mental properties as the very same things as their neurophysiological correlates. Why this should be so is a puzzle, but it cannot show that a mental property and its neurophysiological correlate are not exactly the same thing. “For what is the case cannot be guaranteed by how we conceive of it.”
In this chapter, we have discussed the notion of conceivability both with respect to antimaterialist arguments from conceivability to possibility and to Levine’s claim that conceivability considerations show we cannot explain our mental life in terms of the physical world. We then examined the argument for the explanatory gap that Levine proposes and considered a provisional account of how the gap occurs, revising that account based on further considerations of the nature of identity. Seeking a new account for the explanatory gap, we followed Levine in deploying a new notion of identity to account for it and, finally, we saw how antimaterialists might exploit this new notion and how Levine rebuts them. In conclusion, if there is an explanatory gap, surely Levine is correct to conclude that what we can reasonably say, contra Chalmers et al, is that it is a gap in our understanding of nature, but not one from which we can infer a gap in nature.
An argument from the explanatory gap to the immateriality of the mind, and perhaps even on to a Thomistic conception of the mind, would have had a great chance of penetrating the current debate. But I do not see that it can be accomplished at this time. It certainly seems worthy of further investigation. In the meantime, we proceed to the next chapter to see if there are positive arguments from another source in favor of the view that there is an immaterial aspect to the mind.
The purpose of this chapter is to present a selection of contemporary interpretations of the predominant arguments of St. Thomas Aquinas for the immateriality of the intellect. The original arguments of St. Thomas that are considered and the relevant passages from his works are those suggested by John Haldane in the book Mind, Metaphysics, and Value. The arguments are three in number, from the capacity of the intellect to know all things, from the fact that the operation of the intellect has as its object abstract universals, and from the self-reflexivity of thought. The project is not so much a careful, critical exposition of the arguments as propounded by St. Thomas. Rather, the original lines of reasoning are quoted and briefly explained, then treated as points of departure for contemporary presentations that are founded on the original insights of Aquinas. The first argument is treated at length in a fairly precise and formal version based on the work of Gyula Klima that at first appears promising. A common criticism of the conventional form of the argument will be shared, and it will be shown to miss the mark under Klima’s interpretation of Aquinas’ presentation. However, another criticism along different lines will reveal a fatal weakness in Klima’s approach. The second argument is explicated in two different forms, one due to Mortimer Adler, the other to James Ross. Finally, a recent take by David Braine on the third argument is offered.
In the last paragraphs of his essay on the current state of affairs in philosophy of mind in the Anglo-American analytic school of thought, “The Breakdown of Contemporary Philosophy of Mind,” John Haldane recalls to the attention of the reader three arguments of St. Thomas for the immateriality of the intellect. The arguments are from the capacity of the intellect to know all things, from the fact that the operation of the intellect has as its object abstract universals, and from the self-reflexivity of thought. Haldane makes no claims to have exhausted Aquinas’ proofs in these three; he merely claims they predominate. It is worth knowing, therefore, that David Foster, in his very thorough work classifying the arguments for immateriality in the writings of St. Thomas, adds two more to Haldane’s three: arguments from the possession of the known by the knower and from the possession of contraries by the knower.
I have selected the three in Haldane’s work because he and Foster are in agreement as to what the arguments are and on what their value may be in terms of possible application to present-day debates. As for the two that Foster mentions and which are ignored by Haldane, Foster maintains that both are fairly weak and not likely to be germane in current debates. In particular, the argument from the possession of the known by the knower, he says, is unique to the Summa Contra Gentiles (SCG) and thus does not appear in any later texts; it relies upon a physics that is not readily translatable to our present understanding; and it is not used by current Thomistic thinkers. The argument from the possession of contraries by the knower appears as support for immateriality only in the SCG. In all other works it is an argument for incorruptibility that does not necessarily imply immateriality because of the possibility of incorruptible matter exemplified by the planets. For these reasons the option to exclude these two proofs from the present investigation has been taken and we will remain with Haldane’s selection of three main arguments in Aquinas for the immateriality of the intellect.
The first argument is from the capacity of the intellect to know all things. This is not to be understood in the sense of knowing all that there is to know at once, with omniscience, but in the sense that there is no nature that cannot be more or less grasped by the mind in thought. The second argument is from the fact that the operation of the intellect has as its object abstract universals rather than concrete particulars. It is not this or that three-sided plane figure that is known directly, but triangularity per se. The third argument is based on the experience of the self-reflexivity of thought, the awareness we can have when we are thinking something that we are in fact thinking something.
Haldane does not regard the three arguments to which he refers in St. Thomas as equally compelling, and he does not believe that an exploration of them will be equally fruitful. He singles out the first argument as problematic even in Aquinas’s own terms, and both Haldane and Foster regard it as the least promising of the three. Later we will inspect St. Thomas’ argument in greater detail, but in order to appreciate Haldane’s problem, we will examine a summary of it here.
As a preliminary, we must understand that the proper object of the human intellect for St. Thomas is a “nature existing in corporeal matter.” So we are talking here about knowledge of physical things out there in the world. We are talking about material natures. Aquinas’ argument from the capacity of the intellect to know all things depends upon the view that to know something—to grasp it with the mind in thought—is in some way to take on, or possess, its nature. Now it would appear that there is no material thing that cannot be known by the mind in thought. This requires that the intellect be able to possess all material natures. But if the intellect had a material nature, then it could not know all material things, because its having a material nature would have to preclude its taking possession of any other material nature. It could not possess two material natures at the same time, and it could not relinquish its own nature to possess another. So if there is no material nature that the intellect cannot grasp, then there is no material nature that the intellect itself naturally possesses.
The problem with this argument, Haldane says, is that in order to avoid the utter absurdity that one becomes a cat on a mat when one thinks this thought, in speaking of the notion that thinking somehow involves possessing or taking on the nature of its object, St. Thomas must make use of a distinction in the mode of instantiation. One might possess a nature in one mode, intentionally (in esse intentionale), or in another mode, naturally (in esse naturale), or materially. This being so, it would seem that the intellect could receive a form in esse intentionale even though it already possessed that form in esse naturale. That is, it would appear that the intellect could have a material nature, because it might possess its own nature in one manner, and possess the nature of the things it knows in another.
Haldane’s objection occurs in like forms elsewhere in the literature on the argument from the capacity of the intellect to know all things. Foster, for example, makes note of the same problem. There is an interpretation of the proof due to Gyula Klima, however, that takes into account the distinction in modes of instantiation to which Haldane points, and it will be seen that Aquinas might make a case against him based on the distinctions among esse intentionale, esse reale, and esse naturale. Nevertheless, another objection to the argument from Robert Pasnau shows up a fatal assumption in Klima’s version. Prior to the staging and appraisal of Klima’s version of the argument, though, we will examine a more conventional interpretation of it in order to explicate it more fully and understand it better before proceeding to Klima’s more complex and subtle approach.
St. Thomas’s own version of the first argument is from his Summa Theologica (ST):
It must necessarily be allowed that the principle of intellectual operation which we call the soul, is a principle both incorporeal and subsistent. For it is clear that by means of the intellect man can have knowledge of all corporeal things. Now whatever knows certain things cannot have any of them in its own nature; because that which is in it naturally would impede the knowledge of anything else. Thus we observe that a sick man's tongue being vitiated by a feverish and bitter humor, is insensible to anything sweet, and everything seems bitter to it. Therefore, if the intellectual principle contained the nature of a body it would be unable to know all bodies. Now every body has its own determinate nature. Therefore it is impossible for the intellectual principle to be a body.
The two theoretical claims upon which his argument depends are (A) that by means of the intellect a person can have knowledge of all corporeal, or material, things and (B) that whatever knows certain material things cannot have them in its own nature.
Claim (A) is highly unlikely under an interpretation that suggests omniscience, but as noted above, this is certainly not the interpretation that St. Thomas commends. He merely wishes to assert that with respect to the natures of all bodies, there is a general human capacity to know them that in some sense does not seem to be limited. In perception, which involves both the senses and the intellect, there is no material limitation in the sense that we can come to know one real being after another indefinitely. But there is a formal limitation in the sense that the act of perceiving can only reach sensible objects. Nevertheless, because the formal object of the intellect is being, the knowing faculty of the human person is open to all of reality and its aspects inasmuch as everything has being. It seems unlikely that claim (A) could be proved in any way, but “the plausibility of its universality has certainly been enhanced since Aquinas’s day by the spectacular development of the natural sciences, the paradigms of systematic intellective cognition of the nature of bodies.”
Claim (B), that whatever knows certain material things cannot have them in its own nature, can be understood as follows. Cognitive faculties are characterized by their receptivity. They are in potential relative to their proper objects—such as color for the faculty of vision. If the lens of the eye were rose-colored, for example, then the receptivity of the faculty of vision would be compromised since it could not be regarded as in potential to its proper object—color—as its own rose color would taint that which it receives. St. Thomas’s own example, quoted above, is of a sick man whose tongue is rendered faulty by illness so that even what is sweet in itself is bitter to the man’s taste. As a result of acquiring an accidental physical quality due to sickness, the tongue loses its capacity to acquire it proper object. Furthermore, regardless of its condition, whether it be in good health, or have suffered trauma or pathology, as a body, there is one thing that the tongue cannot taste: itself. So there are two kinds of limit to what a corporeal organ, or cognitive faculty depending on such an organ, can apprehend. First, a corporeal cognitive faculty cannot cognize itself and, second, its capacity to cognize another, its proper object, can be mildly to severely restricted, or even eradicated, depending on physical changes in the corporeal organ. Joining claim (A) with our experience of the intellect’s ability to know itself in acts of cognition, we know that the intellective faculty is not limited in either of the two ways delineated. So, while it is true that the senses provide data to the mind for processing, the intellect itself cannot be and cannot use a corporeal organ in its own operation.
The exposition above of St. Thomas’s meaning is a fairly lucid one as it is, but it remains open to Haldane’s criticism, because it does not take into account the different modalities in which a nature may be possessed. That is, since Aquinas does make use of the distinction between possessing a form in esse intentionale and possessing it in esse naturale, it seems possible at first blush that the intellective faculty could be determined by a form on the level of real being in a way that does not affect its capacity to be determined on the level of intentional being. If this gap between the levels of real and intentional being does exist, then it would seem that the intellect could receive a form in esse intentionale even though it already possessed that form in esse naturale, and this is a violation of claim (B).
It may be that Haldane’s objection to the argument can be met, however, if one considers the relationship between the two levels and adds the notion of esse reale. In short, we can answer his objection if there is an interpretation of St. Thomas’s line of reasoning that acknowledges the distinction among ways of being in the intellect and shows a relationship among these modalities that makes their putative independence from each other upon which Haldane hangs his protest impossible. Just such an interpretation is proposed by Gyula Klima.
Klima first suggests a set of four definitions.
(1) A form f in esse reale in a subject s is something that is signified by predicating F of s, and on account of which the subject s is actually F.
(2) A form f′ of an object o in esse intentionale in a subject s is some form f of s in esse reale on account of which s is actually representing o as an F′.
(3) A subject s is actually representing an object o as an F′ if and only if s has some form f in esse reale that is an encoding of some form f′ of o under some natural or artificial system of encoding.
(4) A form f of a subject s is a representing form if and only if f is a form of s in esse reale and it is also a form f′ of an object o in esse intentionale in s.
Perhaps some examples will help to clarify the meanings of the definitions. According to definition (1), if Sam is actually a Fool, it is because Sam really possesses foolishness, and Sam’s foolishness is signified by predicating Fool of Sam. According to definition (2), Sam actually represents Oscar as a Flake because Sam intentionally (not really) possesses the flakiness of Oscar by means of some form that Sam really possesses. Definition (3) may be taken to mean that Sam’s real possession of some form the instantiation of which expresses the flakiness of Oscar in either a natural or artificial system of signification is a necessary and sufficient condition for Sam’s actually representing Oscar as a Flake. Finally, by definition (4), a form possessed by Sam represents the flakiness referred to in ‘Oscar is a Flake’ if and only if that form is really possessed by Sam and it is also the flakiness of Oscar possessed intentionally by Sam.
With these definitions in mind, Klima’s proof of the immateriality of the intellect according to Aquinas goes as follows.
(1) R′ is a range of mutually incompatible forms f′—all material natures—that an object o can really possess.
(2) R is a range of mutually incompatible representing forms f by which a subject s can represent any f′ of R′ under some system of encoding.
(3) Given R and R′, s cannot really possess any f inseparably by its nature.
(3) follows from (1) and (2) because if s really possessed some f inseparably by its nature, then it would always intentionally possess the same f′, namely, the one that is encoded by f. If s always intentionally possessed the same f′, then it could not possess any other f′ intentionally. But if s cannot possess any other f′ intentionally, then it could not represent any f′ of R′, which is contrary to premise (2), the assumption that s can in fact represent any f′ of R′ under some system of encoding. The argument continues by summing up in (4) the result of (1) through (3).
(4) Any representing subject s that can represent all forms f′ belonging to R′, all material natures, is such that s cannot really possess any f belonging to R inseparably by its nature.
(5) The intellective soul is a subject that can represent all forms f′ belonging to R′. (Note: this is a version of claim (A) in the initial discussion of St. Thomas’s argument above.)
(6) So the intellective soul is such that it cannot really possess any f belonging to R inseparably by its nature.
(7) Assume that R = R′. If this is true, then the intellective soul cannot really possess any f′ belonging to R′ inseparably by its nature. Therefore, since R′ is all material natures, then, if R = R′, the intellective soul cannot really possess any material nature inseparably by its nature, so the intellect is immaterial.
(8) Alternatively, assume that R ≠ R′. If this is true, then the intellective soul can really possess some f that is not within R′. But since R′ is all material natures, the f that the intellective soul can really possess is not a material nature, but is some immaterial nature. Therefore the intellect is immaterial.
Klima’s clever interpretation of Aquinas’s original argument saves St. Thomas from Haldane’s complaint that the intellect could receive a form in esse intentionale even though it already possessed that form in esse naturale. More precisely, summarizing the above, Klima says that the form the intellect has in esse reale is an encoding of the form of the object it apprehends, which form it has in esse intentionale. But the form in esse reale, a representing form, or r-form, is not a form that the intellect can really possess inseparably by its nature, because then the intellect by nature could intentionally possess only one form, the form encoded by the r-form it really possesses by nature. It is obviously false that the intellect can only intentionally possess one form and it is a clear violation of the very plausible claim that the mind can know all forms. So the intellect cannot really possess r-forms inseparably by nature. Assume that the range of r-forms is the same as the range of forms that objects can really possess, that is, all material natures, or m-natures. Since the intellect cannot really possess any r-form inseparably by nature, the intellect cannot really possess any m-nature inseparably by nature, contra Haldane. Now assume that the range of r-forms is not the same as the range of forms that objects can really possess, that is, all m-natures. Then the intellect can really possess an r-form that is not among those that can be really possessed by objects. But all m-natures are among those that can be really possessed by objects, so the intellect can really possess r-forms that are not material, and possession of nonmaterial forms entails the immateriality of the intellect. In either case, Haldane’s claim that distinctions among modes of being in the mind might allow for materiality of the intellect seems to be mistaken.
Interestingly, whereas Haldane depends in his critique of Aquinas upon a certain putative independence between esse naturale and esse intentionale, such that the intellect could supposedly possess the same material form both naturally and intentionally, since they are two different modes of possession, Robert Pasnau’s complaint regarding the modes of instantiation relies precisely upon the interdependence he believes St. Thomas would have to assert between the two. Pasnau thinks that Aquinas is committed to the view, for example, that if the intellect really possessed a certain color, then the intellect could not intentionally possess other colors. This is because Aquinas evidently believes that the real existence of any material form x in the intellect would entail the intentional existence of x in the intellect, which in turn blocks the intentional existence of y and z. This seems to be true enough in examples such as the tongue coated with bitterness that can taste things as nothing else but bitter, or the pupil colored red that can only see things as red. But according to Pasnau:
We have no reason to think these examples generalize to all cases, especially where the mind is concerned. There is nothing here that forces us to conclude, for instance, that if the mind were just the gray matter of the brain, the mind would be incapable of thinking of anything other than gray matter. . . . It would be reasonable to follow Aquinas in thinking of cognition in terms of intentional existence, but I see no reason why we should accept a direct link between the intentional and the concrete. The argument . . . takes this link for granted.
Under Klima’s interpretation, however, it seems at first that Pasnau’s complaint may not stand. Putting aside the question whether Klima’s construal accurately represents exactly what Aquinas thought, but regarding it as very much in the Thomistic spirit, we note that Klima makes a crucial distinction between real possession of a form and real possession of a form inseparably by nature. Recall that in his view it is by real possession of a representing form, or r-form, f that the intellect intentionally possesses the form f′ of an object o that it knows. Once again as above, assume that the range of material natures, or m-natures, including the form of gray matter, is the same as the range of r-forms. Now assume for the sake of argument that the intellect really possesses the form of gray matter. Since all m-natures are r-forms, the form of gray matter represents some form f′, and the intellect, in possessing the form of gray matter in esse reale, possesses in esse intentionale whatever form f′ of o is encoded by the form of gray matter. Notice, by the way, that the form of gray matter really possessed by the intellect need not encode f′ of o as the form of gray matter. That is, the form of gray matter possessed in esse reale by the intellect might represent a completely different f′ of o—it could represent anything. For example, the form of gray matter really possessed by the intellect could represent the form of “dogness” if o is a canine.
At this point we bring in Klima’s distinction between real possession of a form and real possession of a form inseparably by nature. On our assumptions so far, the intellect possesses the form of gray matter, which form is an r-form, and thus the intellect intentionally possesses some form of an object, say, “dogness.” Now if the intellect really possessed the form of gray matter inseparably by nature, then the intellect by nature could represent nothing other than “dogness.” It is clearly false that the intellect by nature can represent only “dogness.” Therefore, the intellect does not possess the form of gray matter inseparably by nature. The same would be true for any material form that we substituted for the form of gray matter. So we may conclude, in this case, that the intellect does not really possess inseparably by nature any material form. That is to say, the intellect is immaterial.
To complete the argument, we now assume that the range of r-forms is not the same as the range of m-natures. Regrettably, at this crucial point, trouble begins. The problem is in Klima’s point (8) above; namely, in his assumption about what it means to say that the range of r-forms is not the same as the range of m-natures. Klima assumes that to say the range of r-forms is not the same as the range of m-natures is to say either (A) m-natures are a subset of r-forms or (B) the two ranges are disjoint. It is not clear which he intends, and he completely ignores the possibility that (C) r-forms are a subset of m-natures. The problem is that there is no compelling reason for a materialist to grant (A) or (B) when (C) is also an option. (A) says that every m-nature is an r-form, but some r-forms are not m-natures. But why should a materialist grant that? The claim that some r-forms are not m-natures is akin to the claim about the immateriality of the intellect that Klima is trying to prove in the first place. (B) says that no r-forms are m-natures. Again, there is no reason for a materialist to grant this. Finally, (C) says every r-form is an m-nature, but some m-natures are not r-forms. No doubt the materialist would be happy with (C), since all forms are material and—who knows—perhaps gray matter is a non-representational form that would not stick the intellect with one form in esse intentionale.
It is ironic that Klima’s argument only works on the assumption that all representing forms are material natures. The great difficulty, of course, is that the proof requires one to accept beforehand the existence of immaterial forms. I would love to find a way around this problem, since there are elements of Klima’s exposition that are brilliant. But, at this point, we might have to accept the opinions of Haldane, Foster, and Pasnau that the argument from the capacity of the intellect to know all things is weak indeed.
Having concluded that the first argument faces serious challenges, we turn to St. Thomas’s second argument for the immateriality of the intellect from the fact that the operation of the intellect has as its object abstract universals rather than concrete particulars.
We may proceed from the specific notion of the human soul inasmuch as it is intellectual. For it is clear that whatever is received into something is received according to the condition of the recipient. Now a thing is known in as far as its form is in the knower. But the intellectual soul knows a thing in its nature absolutely: for instance, it knows a stone absolutely as a stone; and therefore the form of a stone absolutely, as to its proper formal idea, is in the intellectual soul. Therefore the intellectual soul itself is an absolute form, and not something composed of matter and form. For if the intellectual soul were composed of matter and form, the forms of things would be received into it as individuals, and so it would only know the individual: just as it happens with the sensitive powers which receive forms in a corporeal organ; since matter is the principle by which forms are individualized. It follows, therefore, that the intellectual soul, and every intellectual substance which has knowledge of forms absolutely, is exempt from composition of matter and form.
The following treatment of St. Thomas’s point in the passage above is guided largely, though by no means exclusively, by Mortimer Adler.
The difference between knowing abstract universals and knowing concrete particulars, and the difference it makes, may be shown by a simple example. Let us say that we have a variety of cardboard cut-outs before us and each one describes a three-sided plane figure with three angles. The relationships of angles to sides, the color, size, and thickness of the cards, to name a few qualities, could all be varied. These are the material facts that define each card, and this is characteristic of material facts: they define the features of a particular situation or thing as particular. Yet each card can be thought of as a triangle and the concept we have of triangularity is applied without regard to the details of the qualities above, or any others, because our idea of a triangle—our concept of the essence of triangularity—is one from which all of these qualities are excluded. This is peculiar, because there is no particular individual card that can be like this concept. The actual existence of the shapes of the cards is subject to material conditions. Furthermore, it is only the concrete, individual card that we are able to sense. Nevertheless we grasp a universal abstract concept of triangularity when we perceive the particular cards. This is because perception is the operation of sense and intellect working together. As St. Thomas notes, it is the peculiar power we call intellect that is able to abstract essences and apprehend universal concepts, and it is from this ability that he infers the intellect is exempt from composition of matter and form, that is, that the intellective soul is immaterial.
The first proposition of the second argument for immateriality of the intellect has been suggested: The concepts by which we know individuals to be of this or that kind consist of meanings that are universal. The second proposition is this: Nothing embodied in a composition of matter and form, that is, nothing physical, could ever actually be universal. Any embodied being exists as a particular, individual, concrete thing and could at best be only an instance of this or that kind. The conclusion is that abstract universal concepts cannot be embodied in matter, and thus cannot be realized in corporeal organs of the human being. In particular, we must say that if concepts existed in, or were acts of, the human brain, they could not have the character of universality which they have that enables us to think of abstract universal objects, such as kinds, as opposed to the concrete, particular individuals that are the objects of sense-perception, imagination, and memory. Therefore we must regard the power by which we apprehend concepts, that is, the intellect, as an immaterial power the operation of which does not belong to a bodily organ, specifically, the brain.
The first proposition—that the concepts by which we know individuals to be of this or that kind consist of meanings that are universal—may be defended by a consideration of how we identify kinds of things. The names we have for the kinds of things we know are common and general names. We may speak of animals and shapes, triangles and cats. The common names we use have meanings that derive from the universal concepts we possess. The names themselves are universal; that is, they refer to specific kinds of being—triangles and cats—and not to any particular being that is an instantiation of triangularity or catness. When we want to refer to any cat, setting aside the various material conditions in which all cats must actually exist, such as size, shape, or color, we use the common term ‘cat,’ which refers to a kind of animal. Individuals have another class of expressions called proper names by which we refer to them, so that we might signify a particular cat by a name, such as ‘Fluffy.’ Then again individuals might be singled out by definite descriptions, something like ‘the cat on the mat.’ By considering the diverse ways of naming available to us, we come to see that the concepts we have of the various kinds of things we know are the source of both the meanings of the common names that we use to identify those kinds and our understanding of what it is like for a particular thing to be of a specific kind.
The second proposition—that nothing physical could ever actually be universal—is known by consideration of the facts of common experience. As was noted at the head of the discussion of the second argument for immateriality, all of the things that we perceive through our senses are individual things: we hold this triangle in our hand, and we see that cat on the mat. It is not possible for us to see a triangle in general, apart from its material conditions. In fact it is not even possible for us to imagine a triangle in general, since even the image in our mind is subject to material conditions, appearing to us as a certain shape with a particular color. We have never seen or ever imagined a triangle that was not an individual triangle of a certain shape or color. Yet somehow, without reference to any of the material conditions to which every triangle we have ever known has been subject, we are able to apprehend triangularity as such.
In our experience we see that “whatever exists physically exists as an individual, and whatever has individuality exists materially.” Physical or corporeal entities are simply not known to exist with a character that is universal rather than individual. The argument, then, may be summarized as follows. The concepts that we apprehend by the intellect are universal in their signification of objects that are various kinds of things we know, rather than individuals that are particular instances of a kind. Since no physical entity of which we have experiential knowledge has this character of universality, it is reasonable to believe that our concepts cannot exist as physical entities, embodied in matter. Yet concepts exist in the mind as acts of our intellectual power. So we conclude that the intellect cannot be embodied in a material organ, but must be immaterial.
A recent version of the above argument offers an interesting twist on the connection between immateriality and abstract thought by taking into account contemporary concerns about meaning and rule-following that arose in the work of Ludwig Wittgenstein. This argument is due to James Ross. “Ross . . . argues for the immateriality of intellective operations from our ability to understand what we mean despite the fact that material representations of our abstract thought do not disambiguate them from meanings distinct from, but closely related to, the ones we intend.” In order to understand what Ross has in mind, it will help to begin with an example.
Saul Kripke, in discussing a problem first posed by Wittgenstein, proposes the following. Imagine that you are asked to compute 68 + 57, and you have never before done so. In fact, all of the addition you have ever done has been with numbers less than 57. You add the numbers and come up with 125, which is correct in both the mathematical sense and the metalinguistic sense, meaning that by ‘plus’ you intended the same function you have intended in the past, namely, the one that when applied to 68 and 57 yields 125. But now a skeptic enters and claims that if you had really intended the same function, you would have said that 68 + 57 = 5. Of course, this seems crazy—you know what you intended to do. However, the skeptic reminds you that you could not have simply given yourself explicit instructions that 125 is the result of performing the addition in this case. By hypothesis, you have never computed 68 + 57, so you could not have known the result beforehand. Instead, you were applying a rule, the same rule you have always applied when adding. But, asks the skeptic, you have only instantiated the rule for addition a finite number of times. In the past, he continues, the function you were denoting by ‘plus’ might well have been the function ‘quus,’ which returns x + y, if x and y are less than 57, and returns 5 otherwise. You have misinterpreted your own previous usage. You were not using the function ‘plus.’ All along, you have been using ‘quus.’
To be clear, the skeptic is not asking, “How do you know that 68 + 57 is 125?” Rather, the skeptic is asking, “How do you know that ’68 + 57,’ as you meant ‘plus’ in the past, should denote 125?” Perhaps in the past, you intended ‘quus’ and so, if now you intend the same function, you should say that 68 + 57 = 5. You insist that the skeptic is wrong and hunt for a fact about your past usage that will validate your claim to be consistently using ‘plus’ and not ‘quus.’ But the facts of your past usage, all with numbers less than 57, are compatible with your having intended either ‘plus’ or ‘quus.’ That is, there is no fact of the matter about which function you intended.
This is where Ross stakes his claim about the immateriality of the intellect. You really do know that you are following the rule for addition. There is a fact of the matter. You are instantiating the pure, abstract function of addition, apart from any and all particularities of past instantiations. This could only be done, Ross claims, if there were an immaterial aspect to the intellect. If there is a fact of the matter about what rule you are following, it cannot be a physical fact. Thinking about the problem in terms of Searle’s critique of computationalism, we might express it this way: if you were merely a physical system, neither you nor anyone else could determine from your past instantiations of addition that you meant ‘plus’ and not ‘quus.’ It should be clear from computer science that different interpretations of the very same physical system are possible. Indeed, there is an indefinite number of interpretations possible. There is nothing about a physical structure that makes it intrinsically a computer, and there is nothing about that same structure that makes it intrinsically an instantiation of one function and not another. The same physical structures can instantiate different functions. In Alfred Freddoso’s terms from above, no purely physical structure can disambiguate our meanings for us. Yet our meanings are disambiguated. We know that when we add, we are using ‘plus’ and not ‘quus.’ Since no physical fact could determine this, there must be an immaterial aspect to the intellect.
The third argument that Aquinas gives for the immateriality of the intellect is based on the experience of the self-reflexivity of thought, the awareness we can have when we are thinking something that we are in fact thinking something. Haldane makes the point that this is best understood not as a second-order act of cognition upon a first-order act, but as an aspect of a single cognitive operation. In the very act of thinking that the cat is on the mat, I may be aware that I am thinking it. It is interesting that he phrases it this way, because there are passages in Aquinas that would appear to flatly contradict Haldane. For example:
The intelligent act of the human intellect is not the act and perfection of the material nature understood, as if the nature of the material thing and intelligent act could be understood by one act; just as a thing and its perfection are understood by one act. Hence the act whereby the intellect understands a stone is distinct from the act whereby it understands that it understands a stone; and so on.
But I think the point that Haldane is trying to make is that Aquinas does not believe in a kind of Lockean introspection that amounts to one intellectual act gazing on another. In that case, Haldane’s point is acceptable.
The line of reasoning for the third argument comes not from the Summa Theologica, but from the Summa Contra Gentiles:
The action of no body is self-reflexive. For it is proved in the Physics that no body is moved by itself except with respect to a part, so that one part of it is the mover and the other the moved. But, in acting, the intellect reflects on itself, not only as to a part, but as to the whole of itself. Therefore, it is not a body.
Self-reflexive consciousness, the ability to simultaneously be aware of something and be aware that we are aware, “to know that we know, to know that we see, to know that we know that we see,” is a truly remarkable characteristic of the mind. Our ability to reflect upon the operations of the intellect, the conscious acts of the mind, and our experiences, is what makes knowledge itself and our ways of knowing possible objects of study. Self-reflexivity is recognized in many relevant areas of research as a true mark of the mental. For example, computer scientist Douglas Hofstadter remarks concerning achievements in artificial intelligence that the “self-understanding and self-monitoring abilities of programs are quite rudimentary, but this idea has emerged as one of the key prerequisites to the attainment of the deep flexibility that is synonymous with genuine intelligence.”
It may be easiest to come to an understanding of the unique capacity of the intellect for self-awareness by comparing it to an act of sense-perception, for example, seeing something. The formal object of sight is color and it is only colored objects that can be apprehended by the faculty of vision. The operation of the faculty of vision, the act of seeing, cannot be attained by that faculty; that is, the act of seeing cannot be performed with seeing itself as its object. The sense of sight cannot become aware of its own acts. Neither can the sense of hearing listen to itself nor the sense of taste savor itself. The external senses cannot have their own acts as their objects. But the intellect, we know from experience, is capable of having the acts of the external senses as its object. We can, for example, make our current act of seeing an object of reflection. The formal object of the intellect does not seem to be limited in the way that the formal objects of the senses are. In fact the boundaries are so wide that, as we know from experience, the intellect has the capacity to apprehend its own acts, to have its own operations as its object, even as it acts.
The difference between the abilities of the external senses and those of the intellect may perhaps be explained by the materiality of the senses, the objects of which are material and the operations of which depend upon bodily organs. As St. Thomas might describe it, bodies by their nature require parts outside of parts, as it were, such that the whole “cannot possibly reflexively compenetrate itself.” Parts A and B might move Part C, Parts B and C might move Part A, and Parts A and C might move Part B, along with various other combinations, but the whole cannot move itself. This is what occurs, however, in self-reflective consciousness, as the intellect is wholly aware of its own operation in the very act of acting, that is, in a single cognitive operation. Thus the intellect acts in a way that would appear to be free of the limits of matter.
A contemporary take on the impossibility of self-reflexivity being an operation exercised in a bodily organ is provided by David Braine. His discussion is founded on the act of judging. The first principle to note is that no isomorphism between any structure in the brain, or any bodily—or even non-material—entity, and some object that is known or understood constitutes a judgment. In other words, having images or representations of any kind in whatever way in the mind as a model of the world is not the same thing as making a judgment. The point is not just that a model requires an interpretive context in order to serve as a model, and that therefore simply having a way of conceiving things cannot count as a model, but that ways of conceiving things and even models have to be put to use in assertive speech-acts in order for real thinking to occur. Having a concept of the essence of a thing is different from knowing and asserting the actual being of the object of knowledge as it is determined by the essence conceived.
When the act of judging is considered, it is not enough to try to imagine some structure in the brain that might somehow relate isomorphically to the object of judgment. Also to be considered is the person making the judgment and the act of judging itself, as an act exhibiting self-reflexivity. If we were to persist with a way of thinking that tried to explain knowledge and judgment as a modeling of the world in the brain as a physical system, then we would find ourselves saddled by the requirement to model in the system not only the object known in the judgment, but also the act of judging itself, and the person doing the judging. This means that the structure in the brain would somehow have to model the act of judgment, including the concomitant act of reflex judgment, that is, the judgment about the act of judgment, as occurs when, for example, one judges that ‘the cat is on the mat’ and simultaneously that ‘I know the cat is on the mat.’ Additionally the physical system would have to model the person making the judgment. In short, to model the act of judging would require a structure in the brain that represents the whole structure that judgment involves, to include the person and ipso facto the model itself.
Since we are speaking of a model in a physical system, the relevant structure would apparently have to be a formal system, one whose elements are manipulated by non-semantical, or mechanical, rules. In other words, the structure would have to be that of a formal language. But it is a principle of formal logic that a formalized language cannot include its own metalanguage. That is, the language by means of which communication about the formal language in question is accomplished cannot be a part of that formal language. But this is exactly what would be required in the loop of self-reflexivity involved in modeling the act of judgment. The formal language would have to be able to “talk about itself” in order to model its own operations, yet this self-reflexivity in a formal language is not possible. On the other hand, this kind of self-reflexivity is clearly possible in natural human languages and in the human mind. So if a material system functioning formally, that is, mechanically, cannot exhibit isomorphism with human beings in respect of the crucial structure of self-reflective thought, then these structures cannot be exercised through a material organ and the intellect is immaterial.
We have examined several contemporary presentations of arguments for the immateriality of the intellect that have their origins in the works of St. Thomas Aquinas. The arguments were based on the capacity of the intellect to know all things, the fact that the operation of the intellect has as its object abstract universals, and the self-reflexivity of thought. It was shown that the first argument, criticized by John Haldane as less compelling than the others, has been given a form in the recent work of Gyula Klima that seems to be able to overcome Haldane’s worries about it. Klima’s interpretation is based on the insight that the capacity of the mind to intentionally possess forms would be unacceptably limited if the representing forms really possessed by the intellect were possessed inseparably by its nature. Since the range of representing forms includes material natures, at least under one assumption, Klima wants to say that the intellect cannot really possess a material nature inseparably by its own nature, and it is therefore immaterial. However, it was discovered during a reconsideration of Klima’s construal, due to a critique from Robert Pasnau, that Klima must assume some claims about the existence of immaterial natures that a materialist would likely regard as begging the question. So Klima fails to repel the attack and the argument ends up falling of its own weight.
The second argument was unraveled with a bit less fuss than the first in a presentation based on the efforts of Mortimer Adler. It was further extended by an argument from James Ross. Adler appeals in his traditional approach to the role of universal concepts in providing the meanings of common names, and to the experience of all physical entities as individual to show that the mind is not matter. Ross appeals to our ability to consistently know unambiguously what we mean by the words we use in a way that no purely physical system could do. With respect to Adler, the question of the nature of concepts has proven to be a very difficult one in the philosophy of mind and many complex interconnecting webs have been spun from various theories. So it is quite possible that his argument could engage contemporary thought in this tangled area where so much is still up for grabs. The benefit of Ross’ argument is that it already directly engages contemporary issues involving major questions and claims about meaning. Finally, the third argument from the work of David Braine showed that no material system operating mechanically can meet the demands of self-representation required by the self-reflexive nature of the act of judgment, and that, therefore, the intellect is immaterial. Since this final argument treats of a central theme of postmodern thought—self-referentiality—it is highly likely that versions of it could attract great interest and approval.
The purpose of the present work was to show the untenability of the leading efforts made so far towards a reductive materialism, and to seek some relief in the exploration of positive arguments in favor of antimaterialism, first based on the nature of consciousness and the explanatory gap, and then in the form of arguments for the immateriality of the intellect. The results have been mixed. It seems clear that reductive materialism is in real trouble and that inasmuch as it still has a hold on the philosophy of mind in the English-speaking world, the condition of that philosophy is lamentable. But what to do about it? John Searle certainly has an appreciation of the state of affairs, but there is something in his thought that suggests he wants to have his cake and eat it too.
With respect to consciousness, it appears that there is no necessary incompatibility between materialism and the existence of an explanatory gap, since the gap in explanation may be seen as representing a gap in our understanding, and not in reality. This being so, one cannot count on deriving an antimaterialist position from the existence of the gap.
Finally, of the three arguments in the Thomistic tradition for the immateriality of the intellect, the first proof—from the capacity of the intellect to know all things—could not be preserved from its own failures. The last two, however, showed promise for some continued reworking that might make them worthy of note in the contemporary situation. The first of these, from the fact that the operation of the intellect has as its object abstract universals, might, in Adler’s version, be further developed in ways that can help plug it into the vast network of competing theories in the unsettled area of philosophy of mind today dealing with the nature and disposition of concepts. Ross’ version is already in touch with contemporary concerns and questions about the meaning of language. And lastly, the argument from the self-reflexivity of thought seems to be the proof best suited for adaptation to current interests, and might achieve the most exciting results, since it delves deeply into a theme much beloved in our so-called postmodern times: self-referentiality.
If the arguments offered make a case at all for the immateriality of the intellect, and if they show potential for dialogue with at least some trends in analytic thought, it would surely be worth the effort to build them up. It is impossible to predict the results. I honestly cannot say, for instance, how the average analytic philosopher would receive an argument ‘from the fact that the operation of the intellect has as its object abstract universals.’ But we ought to render such an argument as rigorous and convincing as possible, in order to make real headway in philosophy of mind, especially if we are, as I think, at the swansong of reductive materialism. But then we would also require some conception of the mind to meet the new demand. This would in turn require adequate philosophies of nature and anthropology. The task is daunting. We must test everything and hold fast to that which is good..
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________. “Conceivability, Explanation, and Defeat.” Philosophical Studies 108 (2002): 327-338.
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Geach, Peter. God and the Soul, 2d ed. South Bend, Indiana: St. Augustine’s Press, 1969.
Haldane, John. “The Breakdown of Contemporary Philosophy of Mind.” In Mind, Metaphysics, and Value in the Thomistic and Analytical Traditions, ed. John Haldane, 54-75. Thomistic Studies, ed. Daniel J. McInerny. Notre Dame: University of Notre Dame Press, 2002.
Henle, S.J., R. J. Theory of Knowledge. Chicago: Loyola University Press, 1983.
Hofstadter, Douglas R. and Daniel C. Dennett, eds. The Mind’s I: Fantasies and Reflections on Self and Soul. New York: Bantam Books, 1988.
Hume, David. A Treatise of Human Nature. Edited with an introduction by Ernest C. Mossner. New York: Penguin Books, 1985.
Kenny, Anthony. Aquinas on Mind. Topics in Medieval Philosophy, ed. John Marenbon. London: Routledge, 1996.
Klima, Gyula. “Aquinas on Immateriality” [course notes in Medieval Philosophy]. New York: Fordham University, accessed 17 May 2004. Available from http://www.fordham.edu/gsas/phil/klima/medphil/Aquinas_on_immateriality.htm; Internet.
Kretzmann, Norman and Eleonore Stump, eds. The Cambridge Companion to Aquinas. Cambridge Companions Series. Cambridge: Cambridge University Press, 1999.
Kripke, Saul. Wittgenstein on Rules and Private Language. Cambridge, Massachusetts: Harvard University Press, 1982.
Levine, Joseph. “Materialism and Qualia: The Explanatory Gap.” Pacific Philosophical Quarterly 64 (1983): 354-361.
________. “On Leaving Out What It’s Like.” In Consciousness: Psychological and Philosophical Essays, eds. G. Humphreys and M. Davies, 121-136. Oxford: Basil Blackwell, 1993. Reprinted in The Nature of Consciousness: Philosophical Debates, eds. Ned Block, Owen Flanagan, and Güven Güzeldere, 543-555. Cambridge, Massachusetts: MIT Press, 1997 (page references are to the reprint edition).
________. “Conceivability, Identity, and the Explanatory Gap.” Plenary session, Tucson III: Toward a Science of Consciousness, April 27-May 2, 1998. Also presented to invited session of World Congress of Philosophy, Boston, Massachusetts, August 10-15, 1998. Available at http://cognet.mit.edu/posters/tucson3/Levine.html; Internet.
________. Purple Haze: The Puzzle of Consciousness. New York: Oxford University Press, 2001.
McGinn, Colin. “Can We Ever Understand Consciousness?” Review of Mind, Language, and Society, by John Searle, and On the Contrary: Critical Essays, 1987-1997, by Paul and Patricia Churchland. New York Review of Books 46 (1999): 44-48. Quoted in Nick Fotion, John Searle, Philosophy Now, ed. John Shand. Princeton: Princeton University Press, 2000.
McGraw, David. “Intellectual Abstraction as Incompatible with Materialism.” Southwest Philosophy Review 11, no. 2 (July 1995): 23-30.
Nagel, Thomas. “What Is It Like to Be a Bat?” Philosophical Review 83 (1974): 435-450.
________. “Brain Bisection and the Unity of Consciousness.” In The Nature of Mind, ed. David M. Rosenthal, 432-440. New York: Oxford University Press, 1991.
Pasnau, Robert. Theories of Cognition in the Later Middle Ages. Cambridge: Cambridge University Press, 1997.
________. Thomas Aquinas on Human Nature. Cambridge: Cambridge University Press, 2002.
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Ross, James. “Immaterial Aspects of Thought.” The Journal of Philosophy 89, no. 3 (March 1992): 136-150.
Savin, Harris. “Introduction: Behaviorism.” In Readings in Philosophy of Psychology, Volume 1, ed. Ned Block. The Language and Thought Series, eds. Jerrold J. Katz, D. Terrence Langendoen, George A. Mille, 11-13. Cambridge, Massachusetts: Harvard University Press, 1980.
Searle, John. Minds, Brains, and Science. Cambridge, Massachusetts: Harvard University Press, 1984.
________. The Rediscovery of the Mind. Cambridge, Massachusetts: The MIT Press, 1994.
________. The Mystery of Consciousness. Including Exchanges with Daniel C. Dennett and David J. Chalmers. New York: New York Review of Books, 1997.
________. “The Nature of Consciousness.” Class notes. Graduate Seminar, January-May. University of California at Berkeley, 2005.
Skinner, B. F. “Selections from Science and Human Behavior.” In Readings in Philosophy of Psychology, Volume 1, ed. Ned Block. The Language and Thought Series, eds. Jerrold J. Katz, D. Terrence Langendoen, George A. Mille, 37-47. Cambridge, Massachusetts: Harvard University Press, 1980.
Swinburne, Richard. The Evolution of the Soul. Oxford: Clarendon Press, 1986.
Thomas Aquinas. The Summa Theologica of St. Thomas Aquinas. Translated by the Fathers of the English Dominican Province. New York: Benziger Brothers, Inc., 1947.
________. Summa Contra Gentiles. Translated by James F. Anderson. Notre Dame: University of Notre Dame Press, 1975.
 Some prefer ‘physicalism’ to ‘materialism,’ in order to avoid confusion with the sense of ‘materialism’ that implies gross neglect of higher concerns in favor of baser desires for money or other material wealth, or in order to press the point that what we are talking about is that which is studied in physics, or various other reasons. It should go without saying that I do not mean ‘materialism’ in the sense of neglect of higher concerns, and I have no use for any other distinctions between ‘physicalism’ and ‘materialism,’ so I will stick with the latter, although I will certainly speak of things as ‘physical.’
 This terminology is due to Martin Davies, “The Philosophy of Mind,” in Philosophy 1: A Guide through the Subject, ed. A. C. Grayling (Oxford: Oxford University Press, 2000), 257.
 Book-length treatments include Richard Swinburne, The Evolution of the Soul (Oxford: Clarendon Press, 1986) and J. Foster, The Immaterial Self: A Defence of the Cartesian Dualist Conception of the Mind (London: Routledge, 1991); for an essay, see Howard Robinson, “Dualism,” in The Blackwell Guide to Philosophy of Mind, eds. Stephen P. Stich and Ted A. Warfield, 85-101 (Oxford: Blackwell Publishing, Ltd., 2003).
 John Searle, The Rediscovery of the Mind (Cambridge, Massachusetts: The MIT Press, 1994), 28. This will come up later, but, in a nutshell, Searle sees nothing inconsistent in the view that one can accept what he regards as the obvious facts of physics—for example, that the world is made up entirely of particles in fields of force—along with the obvious facts of our experience—for example, that we have conscious mental states with irreducible phenomenological properties. (Although this may sound like property dualism, Searle vehemently denies that he is a property dualist.) I would take exception to Searle’s claim that “the world is made up entirely of particles in fields of force” is a fact of physics. It would seem to me to be more like an underlying assumption.
 Davies, 255-256.
 This is not to make the mistake of saying that Descartes, therefore, is the sole source of the problems this influence has caused. No thinker exists in a vacuum, and surely Descartes was as much a transmitter as an originator of ideas. So I have tried to lay the blame on substance dualism, and not on Descartes, although his name is assuredly the first we associate with that theory.
 Discourse on the Method, Part IV, 32; Meditations on First Philosophy, Meditation VI, 78.
 Paul M. Churchland, Matter and Consciousness, Revised Ed. (Cambridge, Massachusetts: The MIT Press, 1988), 20; for one dramatic account of the effects on the mental lives of patients after the surgical severing of their corpores callosa, which serve as communications channels between the two halves of the brain, see Thomas Nagel, “Brain Bisection and the Unity of Consciousness,” in The Nature of Mind, ed. David M. Rosenthal, 432-440 (New York: Oxford University Press, 1991).
 Of course, a substance dualist could make this claim too.
 Harris Savin, “Introduction: Behaviorism,” in Readings in Philosophy of Psychology, Volume 1, ed. Ned Block, The Language and Thought Series, eds. Jerrold J. Katz, D. Terrence Langendoen, George A. Mille (Cambridge, Massachusetts: Harvard University Press, 1980), 11.
 B. F. Skinner, “Selections from Science and Human Behavior,” in Readings in Philosophy of Psychology, Volume 1, ed. Ned Block, The Language and Thought Series, eds. Jerrold J. Katz, D. Terrence Langendoen, George A. Mille (Cambridge, Massachusetts: Harvard University Press, 1980), 42.
 Davies, 257.
 Hilary Putnam, “Brains and Behavior,” in Readings in Philosophy of Psychology, Volume 1, ed. Ned Block, The Language and Thought Series, eds. Jerrold J. Katz, D. Terrence Langendoen, George A. Mille, 24-36 (Cambridge, Massachusetts: Harvard University Press, 1980).
 Searle, The Rediscovery of the Mind, 35.
 Robert Cummins, Meaning and Mental Representation (Cambridge, Massachusetts: The MIT Press, 1991), 124.
 Searle, The Rediscovery of the Mind, 37-38.
 Ibid., 36-37.
 Example: Pennies are a type of coin, and this penny is a token of the type.
 Searle, The Rediscovery of the Mind, 40.
 Describing conscious mental states in terms of there being something it is like to be in such states is a commonplace in contemporary philosophy of mind due to Thomas Nagel, “What Is It Like to Be a Bat?” Philosophical Review 83 (1974): 435-450.
 Ned Block and Jerry A. Fodor, “What Psychological States Are Not,” in Readings in Philosophy of Psychology, Volume 1, ed. Ned Block, The Language and Thought Series, eds. Jerrold J. Katz, D. Terrence Langendoen, George A. Mille (Cambridge, Massachusetts: Harvard University Press, 1980), 244-245.
 Searle, The Rediscovery of the Mind, 43.
 Ned Block, “Troubles with Functionalism,” in Readings in Philosophy of Psychology, Volume 1, ed. Ned Block, The Language and Thought Series, eds. Jerrold J. Katz, D. Terrence Langendoen, George A. Mille (Cambridge, Massachusetts: Harvard University Press, 1980), 276-277.
 Searle, The Rediscovery of the Mind, 43.
 Cummins, 124.
 Peter Geach, God and the Soul, 2d ed. (South Bend, Indiana: St. Augustine’s Press, 1969), 40.
 By this, of course, I mean they have not answered them to my satisfaction. I do not wish to leave the reader with the impression that computationalists are silent on the matter. Far from it.
 John Searle, Minds, Brains, and Science (Cambridge, Massachusetts: Harvard University Press, 1984), 31-33.
 The full version is Searle, The Rediscovery of the Mind, 197-226.
 Churchland, 43-44. The following examples are Churchland’s.
 Ibid., 44.
 Ibid., 43.
 Ibid., 45-47.
 Ibid., 46.
 Searle, The Rediscovery of the Mind, 48.
 It is ironic that some radical skeptics have inductively argued in the same way against belief in the entities postulated by the natural sciences. We know from history, they say, that scientific theories rise and fall, and with them, their concepts and the entities they posit. So why should we trust our current theories?
 Searle, The Rediscovery of the Mind, 58-63. The following treatment of folk psychology is due to Searle.
 Ibid., 59.
 Ibid., 60.
 Ibid., 61.
 Nick Fotion, John Searle, Philosophy Now, ed. John Shand (Princeton: Princeton University Press, 2000), 241.
 Searle, Rediscovery of the Mind, 1. Although this quote may give the impression that Searle wants to rob us of our sense of amazement at the phenomena of consciousness, this is not true, and it would be unfair to leave the reader with that impression. The following quote from Searle, Minds, Brains, and Science, 15-16, ought to settle the matter: “I think the existence of consciousness ought to seem amazing to us. It is easy enough to imagine a universe without it, but if you do, you will see that you have imagined a universe that is truly meaningless. Consciousness is the central fact of specifically human existence because without it all of the other specifically human aspects of our existence—language, love, humour, and so on—would be impossible. I believe it is, by the way, something of a scandal that contemporary discussions in philosophy and psychology have so little of interest to tell us about consciousness.”
 Ibid., 227.
 These four points and much of the material below are from John Searle, “The Nature of Consciousness,” class notes, Graduate Seminar, January-May, University of California at Berkeley, 2005.
 John Searle, The Mystery of Consciousness, including exchanges with Daniel C. Dennett and David J. Chalmers (New York: New York Review of Books, 1997), 7.
 Searle, Minds, Brains, and Science, 20-23.
 Colin McGinn, “Can We Ever Understand Consciousness?” review of Mind, Language, and Society, by John Searle, and On the Contrary: Critical Essays, 1987-1997, by Paul and Patricia Churchland, New York Review of Books 46 (1999): 44-48; quoted in Fotion, 246.
 David J. Chalmers, The Conscious Mind: In Search of a Fundamental Theory (Oxford: Oxford University Press, 1996).
 Joseph Levine, “Materialism and Qualia: The Explanatory Gap,” Pacific Philosophical Quarterly 64 (1983): 354-361, made “explanatory gap” an every-day expression in philosophy of mind.
 There is a vast and interesting body of literature on this question of the conceivability of “zombies,” that is, creatures who are molecule-for-molecule duplicates of us but lack any conscious mental life.
 David J. Chalmers speaking for himself in an exchange with Searle in Searle, The Mystery of Consciousness, 164.
 Gordon Barnes, “Should Property-Dualists Be Substance-Hylomorphists?” in Person, Soul, and Immortality: Proceedings of the American Catholic Philosophical Association 75 (2001), ed. Michael Baur, 285-299 (Charlottesville, Virginia: Philosophy Documentation Center, 2002).
 “Body and soul are not two actually existing substances; rather, the two of them together constitute one actually existing substance. For man’s body is not actually the same while the soul is present and when it is absent; but the soul makes it to be actually,” SCG II, 69, 2.
 Joseph Levine, “Conceivability, Identity, and the Explanatory Gap,” plenary session, Tucson III: Toward a Science of Consciousness, April 27-May 2, 1998, also presented to invited session of World Congress of Philosophy, Boston, MA, August 10-15, 1998, available at http://cognet.mit.edu/posters/tucson3/Levine.html , 7.
 Joseph Levine, Purple Haze: The Puzzle of Consciousness (New York: Oxford University Press, 2001).
 Meditations on First Philosophy, Meditation VI, 78.
 A Treatise of Human Nature, Bk. I, Part II, Sec. II. Some regard this as almost obviously false, since it seems we could easily imagine something in contradiction to the conclusion of a complex mathematical proof, for example. But the debate is beyond the scope of the present work.
 Levine, “Conceivability, Identity, and the Explanatory Gap,” 1.
 David J. Chalmers, “Consciousness and Its Place in Nature,” in The Blackwell Guide to Philosophy of Mind, eds. Stephen P. Stich and Ted A. Warfield (Oxford: Blackwell Publishing, Ltd., 2003), 106.
 Gordon Barnes, “Conceivability, Explanation, and Defeat,” Philosophical Studies 108 (2002): 327.
 Barnes, 336.
 Levine, Purple Haze, 80.
 Ibid., 68.
 Ibid., 79.
 Although the comparison does appear in Levine, Purple Haze, for the sake of clarity, the formulation of the comparison used here is from Levine, “Conceivability, Identity, and the Explanatory Gap.”
 Joseph Levine, “On Leaving Out What It’s Like,” in Consciousness: Psychological and Philosophical Essays, eds. G. Humphreys and M. Davies, 121-136 (Oxford: Basil Blackwell, 1993); reprinted in The Nature of Consciousness: Philosophical Debates, eds. Ned Block, Owen Flanagan, and Güven Güzeldere (Cambridge, MA: MIT Press, 1997), 540 (page references are to the reprint edition).
 If John Searle’s unpublished suggestion regarding Saul Kripke’s work is correct, that is, if there is no such thing as “metaphysical necessity,” but instead “Water is H2O” is an analytic truth, then this is of course superfluous, because “Water is H2O” provides its own analyticity, as it were. But Levine will ultimately reject this account anyway for reasons given below.
 Levine, “Conceivability, Identity, and the Explanatory Gap,” 3.
 Levine, Purple Haze, 83.
 Ibid., 81.
 Levine, “Conceivability, Identity, and the Explanatory Gap,” 5.
 Levine, Purple Haze, 82.
 Ibid., 83.
 Levine, “Conceivability, Identity, and the Explanatory Gap”, 6.
 Ibid., 7.
 Levine, Purple Haze, 91.
 Levine, “Conceivability, Identity, and the Explanatory Gap,” 7.
 Robert Pasnau, Thomas Aquinas on Human Nature (Cambridge: Cambridge University Press, 2002), 52, makes the point that, strictly speaking, the arguments for immateriality apply to the principle of intellectual operation, which St. Thomas identifies with the human soul, of which the intellect is a power. However, rigor with respect to terminology is not pertinent in this case, so I will continue to speak of the intellect.
 John Haldane, “The Breakdown of Contemporary Philosophy of Mind,” in Mind, Metaphysics, and Value in the Thomistic and Analytical Traditions, ed. John Haldane, Thomistic Studies, ed. Daniel J. McInerny (Notre Dame: University of Notre Dame Press, 2002), 72-75.
 David Ruel Foster, “Aquinas’s Arguments for Spirit,” in Religions and the Virtue of Religion: Proceedings of the American Catholic Philosophical Association 65 (1991), eds. Thérèse-Anne Druart and Mark Rasevic (Charlottesville, Virginia: Philosophy Documentation Center, 1992), 239-242.
 Both agree that of the three, the first—from the capacity of the intellect to know all things—is least likely to work in modern contexts. They both recommend the remaining two for further consideration and reworking in contemporary frameworks. Regrettably, this has yet to occur, and hardly any such reworkings may be found. Robert Pasnau, Theories of Cognition in the Later Middle Ages (Cambridge: Cambridge University Press, 1997), 56, n.56, states that he knows of no adequate treatment on this topic.
 Foster, “Aquinas’s Arguments for Spirit,” 240.
 Ibid., 242.
 Intellect is the capacity for thought and understanding. Properly speaking ‘mind’ and ‘intellect’ ought to be distinguished, since Aquinas regards the mind as both intellect, the power of apprehension, and will, the power of appetition. But for the purposes of this work there is no need to insist upon this distinction and the terms ‘intellect’ and ‘mind’ may be used interchangeably.
 ST I, 84, 7.
 Haldane, 72.
 Foster, “Aquinas’s Arguments for Spirit,” 243.
 In this work I will sometimes use expressions like “possess intentionally,” “possess really,” and “possess naturally” to indicate these three modes of possession respectively.
 ST I, 75, 2.
 Norman Kretzmann and Eleonore Stump, eds., The Cambridge Companion to Aquinas, Cambridge Companions Series (Cambridge: Cambridge University Press, 1999), 132.
 R. J. Henle, S.J., Theory of Knowledge (Chicago: Loyola University Press, 1983), 167.
 Kretzmann and Stump, 132. However, Michael Dodds, O.P., pointed out to me that some sciences, e.g., quantum mechanics, do seem to imply certain limits. Moreover, Mark Delp says Kretzmann and Stump miss the mark here, since Aquinas, when he speaks of our ability to know all things, is talking about simple apprehension, rather than judgment or reasoning.
 It is not my intention to confuse sense organs and sense faculties, just to make a simple point with a clear example.
 Kretzmann and Stump, 132.
 If you were by accident to bite off the tip of your tongue, would you taste your own tongue? Although you would probably still speak of it as your tongue, with some sense of ownership, it is, in another important sense, really a piece of flesh that is not your tongue, having been cut off from you, no longer a part of you, ceasing its organic function, etc. Your tongue is not that. I mention this because Anthony Kenny, Aquinas on Mind, Topics in Medieval Philosophy, ed. John Marenbon (London: Routledge, 1996), 132, claims that Aquinas is wrong, because, among other things, it is obviously false that a tongue does not have its own taste. But I think perhaps one could make a case for St. Thomas.
 Gyula Klima, “Aquinas on Immateriality” [course notes in Medieval Philosophy] (New York: Fordham University, accessed 17 May 2004); available from http://www.fordham.edu/gsas/phil/klima/medphil/Aquinas_on_immateriality.htm ; Internet. Whether or not Klima’s work is intended and produced as a direct response to Haldane, I do not know; I am only using it as such.
 Although I will not directly quote Klima’s argument in toto here, so as to allow further elucidation on my part within the argument where deemed necessary, my paraphrase will not stray far from his wording because of the need to maintain the precision of his reasoning.
 Pasnau, Thomas Aquinas on Human Nature, 56-57.
 Ibid., 57.
 The suggestion that there is a form of gray matter is whimsical—I am, of course, only making a point using Pasnau’s own example.
 It follows that Pasnau is incorrect in his assertion that Aquinas is committed to the view that the real existence of any material form x in the intellect would entail the intentional existence of x in the intellect, at least under Klima’s interpretation.
 ST I, 75, 5.
 Mortimer Adler, Intellect: Mind Over Matter (New York: Macmillan Publishing Company, 1990), 49-53.
 David McGraw, “Intellectual Abstraction as Incompatible with Materialism,” Southwest Philosophy Review 11, no. 2 (July 1995): 24.
 Henle, S.J., 42.
 Adler, 49.
 Ibid., 50.
 James Ross, “Immaterial Aspects of Thought,” The Journal of Philosophy 89, no. 3 (March 1992): 136-150.
 Alfred J. Freddoso, “Good News, Your Soul Hasn’t Died Quite Yet,” in Person, Soul, and Immortality: Proceedings of the American Catholic Philosophical Association 75 (2001), ed. Michael Baur (Charlottesville, Virginia: Philosophy Documentation Center, 2002), 88.
 Saul Kripke, Wittgenstein on Rules and Private Language (Cambridge, Massachusetts: Harvard University Press, 1982), 8-20.
 Ibid., 12.
 Haldane, 72.
 Notice that we can have such an awareness, we may be aware of what we are thinking or perceiving, but it will not always be so. If you were to open your bedroom door and see a tiger lunging at you, it is unlikely you would think, “I am aware of seeing a tiger.” Rather, you would just see the tiger and slam the door. This point was made to me by Michael Dodds, O.P.
 ST I, 87, 3.
 SCG II, 49, 8.
 Henle, S.J., 44.
 Douglas R. Hofstadter and Daniel C. Dennett, eds., The Mind’s I: Fantasies and Reflections on Self and Soul (New York: Bantam Books, 1988), 282.
 Henle, S.J., 45.
 Ibid., 46.
 David Braine, The Human Person: Animal and Spirit (Notre Dame, Indiana: University of Notre Dame Press, 1992), 466-472.
 Ibid., 466-467.
 Ibid., 467.
 Paraphrase of 1 Thessalonians 5:21.