Some brief arguments for dualism
It is unreasonable to expect even the best argument for a controversial philosophical position to be capable, in one fell swoop and all by itself, of convincing the most skeptical opponent – or, indeed, even to move him slightly in the direction of reconsidering his position. That is (usually, anyway) simply not how the human mind works. A dispute over some particular argument for the existence of God, mind-body dualism, or traditional sexual morality (to take just three examples) can reflect a tacit disagreement about fundamental metaphysical assumptions that is so deep and unconscious that the parties to the dispute (or at least one party, usually the skeptical or “naturalist” one) are barely aware that it exists at all, and often talk past each other as a result. What seems like an obvious objection to an argument can often constitute in reality a failure to see the point of the argument, and in particular a failure to see that what the argument does is precisely to call into question the intelligibility or rational justifiability of the objection itself. While the argument in question can in many cases be stated fairly simply and straightforwardly, pages and pages, indeed an entire book, might be required in order to set the stage so that its terms and basic assumptions are properly understood, and that countless point-missing objections might patiently be swept away like so much intellectual rubbish standing in the way of understanding.
Some common objections to dualism are like this. They falsely assume, for example, that any argument for dualism must be something analogous to a “God of the gaps” argument – a “soul of the gaps,” as it were – which seeks to exploit some current lacuna in our knowledge of the brain and to suggest that the “hypothesis” of an immaterial substance might explain what neuroscientists have so far been unable to. It is then objected that such an explanation would violate Ockham’s razor, that neuroscience has already “explained” x, y, and z and thus can be expected to explain everything else, etc. etc. I hear these objections frequently. They are often presented by people who mean well, and who are not entirely uninformed about some of the arguments presented by both materialists and anti-materialists in the philosophy of mind. But they nevertheless reflect a very shallow understanding of the debate. For the main arguments for dualism do not have this structure at all. They are not quasi-scientific “explanatory” “hypotheses” which “postulate” the existence of this or that as one way among others (albeit the most “probable”) of “accounting for” “the evidence.” They are intended rather as strict metaphysical demonstrations. They either prove conclusively that the mind is immaterial or they prove nothing. And if they work, there can be no question of the materialist looking for other possible ways to explain “the data.” For the existence of an immaterial mind, or an immaterial aspect to the mind, will, given such a proof, simply have itself to be taken as a piece of data for which any acceptable theory has to account.
Again, this doesn’t mean that one should judge such arguments based on one’s immediate reaction to a first reading; to prove something conclusively doesn’t mean to prove it instantly, to the immediate satisfaction of the most hostile and stubborn skeptic. Even properly understanding an argument, especially in metaphysics, can require a great deal of effort and sustained thought. Still, some dualist arguments are straightforward enough that at least their basic thrust can be put fairly succinctly, even if a complete treatment would require various further explanations of this or that premise or key concept. In this post and several succeeding ones I want to present some of these arguments, in as brief a form as possible. (Further elaboration can be found in my books Philosophy of Mind and The Last Superstition.)
One aspect of the mind that philosophers have traditionally considered particularly difficult to account for in materialist terms is intentionality, which is that feature of a mental state in virtue of which it means, is about, represents, points to, or is directed at something, usually something beyond itself. Your thought about your car, for example, is about your car – it means or represents your car, and thus “points to” or is “directed at” your car. In this way it is like the word “car,” which is about, or represents, cars in general. Notice, though, that considered merely as a set of ink marks or (if spoken) sound waves, “car” doesn’t represent or mean anything at all; it is, by itself anyway, nothing but a meaningless pattern of ink marks or sound waves, and acquires whatever meaning it has from language users like us, who, with our capacity for thought, are able to impart meaning to physical shapes, sounds, and the like.
Now the puzzle intentionality poses for materialism can be summarized this way: Brain processes, like ink marks, sound waves, the motion of water molecules, electrical current, and any other physical phenomenon you can think of, seem clearly devoid of any inherent meaning. By themselves they are simply meaningless patterns of electrochemical activity. Yet our thoughts do have inherent meaning – that’s how they are able to impart it to otherwise meaningless ink marks, sound waves, etc. In that case, though, it seems that our thoughts cannot possibly be identified with any physical processes in the brain. In short: Thoughts and the like possess inherent meaning or intentionality; brain processes, like ink marks, sound waves, and the like, are utterly devoid of any inherent meaning or intentionality; so thoughts and the like cannot possibly be identified with brain processes.
You can, as I have implied, look at this as just a “puzzle” for materialism – one which might be solved by developing a complex functional analysis of mental states, or by framing materialism in terms of the concept of “supervenience” rather than identity or reduction, or whatever. Or you can see it as a very simple and straightforward statement of an objection that, while it can also be formulated in much more sophisticated and technical terms and in a way that takes account of and preempts the various objections materialists might try to raise against it, nevertheless goes to the core of the problem with materialism, and indeed shows why materialism cannot be true. This latter view is the one I endorse. I maintain that the problem for materialism just described is insuperable. It shows that a materialist explanation of the mind is impossible in principle, a conceptual impossibility. And the reason has in part to do with the concept of matter to which materialists themselves are at least implicitly committed. Some of the further posts in this series will develop this suggestion. Along the way we will see (among other things) that the common materialist claim that “everything else has been explained in materialist terms” is an urban legend, based on nothing more than conceptual sleight of hand coupled with historical ignorance. Stay tuned.
Following Aristotle, the Scholastic tradition famously held that final causes – goal-directedness, purposiveness, natural ends – permeate the natural world. Contrary to a popular misconception, this does not mean that they thought that everything in the world has a purpose or function in the sense that biological organs have purposes or functions. Hence it is no good to accuse them of thinking, absurdly, that piles of dirt, asteroids, mountain ranges, and the like simply must play some role within the universe as a whole that is somehow analogous to the role hearts and kidneys play in the body. Functions like the kind bodily organs play constitute only one, relatively rare, kind of final causality. Nor did they think that final causality is generally associated with anything like consciousness. For an Aristotelian to say that a plant by virtue of its nature “wants” to grow is just a figure of speech. Literally speaking the plant does not, of course, want anything at all, since it is totally unconscious. It is only in us, and in certain other animals, that final causes are associated with conscious awareness.
What the Scholastics did have in mind is summed up in Aquinas’s dictum that “every agent acts for an end,” otherwise known as the “principle of finality.” By an “agent” he means that which brings about or causes some effect. And what he is saying is that when a certain cause generates a certain effect or range of effects in a law-like way (as we would say today) that is only because it naturally “points to“ or is “directed towards” that effect or range of effects as its proper end. For example, a match when struck will, unless prevented (e.g. by being water damaged), generate flame and heat – and flame and heat specifically rather than frost and cold, or the smell of lilacs, or no effect at all. It has an inherent causal power to bring about that effect specifically. What Aquinas and the other Scholastics argued is that unless we acknowledge the existence of such inherent powers, unless we recognize that whenever a certain efficient cause A generates its effect B that is only because the generation of B is the final cause or natural end of A, then we have no way of making intelligible why it is exactly that A generates B specifically rather than some other effect or no effect at all. The existence of final causes is, in this sense, a necessary condition for the existence of efficient causes – of, that is to say, causation as modern philosophers tend to understand it. This is one reason Aquinas held the final cause to be “the cause of causes.”
Now modern philosophy, and in particular modern philosophy’s conception of science, is defined more than anything else by its rejection of final causes. Indeed, as philosophers like William Hasker and David Hull have pointed out, at this point in the history of science, what remains of the “mechanistic” picture of the natural world which we have inherited from the early moderns is really nothing but this rejection. As I argue in The Last Superstition, there has never really been any serious philosophical case for this rejection; it was, and still is, more ideologically than intellectually motivated. Moreover, there are in my view (and, again, as I argue in TLS) overwhelming reasons to think it was a mistake. One of them is that, as Hume’s famous puzzles illustrate, causation has indeed become seriously problematic in modern philosophy in exactly the way Aquinas’s analysis would lead us to expect it to, given the abandonment of final causes.
The abandonment of final causes has also crucially contributed to the creation of the “mind-body problem,” something that did not exist, certainly not in anything like the form familiar to contemporary philosophers, prior to the moderns’ rejection of the Aristotelian-Scholastic metaphysical framework. For to insist that the material world is utterly devoid of final causes – devoid, that is to say, of anything that inherently “points to” or is “directed toward” anything beyond itself – is implicitly to deny that intentionality could possibly be material, for intentionality, of course, is just the mind’s capacity to point to or be directed towards something beyond itself, as it does in thought. (See my previous post in this series.) Hence to insist that the material world is devoid of any inherent final causes while at the same time acknowledging the existence of intentionality is implicitly to commit oneself to dualism. Indeed, this is surely one reason why Descartes, one of the fathers of the “mechanistic” revolution in science, was a dualist. Far from being a kind of pre-scientific holdover, dualism of the broadly Cartesian sort is a logical consequence of the turn to mechanism that defined the scientific revolution.
The only way to hold on to the mechanistic conception of nature while rejecting dualism is thus to deny the existence of intentionality. And that is why, as John Searle has argued, all extant forms of materialism do indeed implicitly deny its existence, and thus (I would say) amount to disguised forms of eliminative materialism. This is halfway admitted by Jerry Fodor when he writes, as he does in Psychosemantics, that “if aboutness [i.e. intentionality] is real, it must be really something else.” That is to say, intentionality per se simply cannot be real given the mechanistic conception of the material world that Fodor, like all materialists, has inherited from the early modern philosophers. Hence the most the materialist can do is try to substitute for it some physicalistically “respectable” ersatz. But this is simply eliminative materialism in “folk psychological” drag; and eliminative materialism, however you dress it up, is simply incoherent. (Yet again, see TLS, and in particular chapter 6, for the details.)
We have, then, another brief argument for dualism, which can be summarized as follows: If materialism is true, then (given that it is committed to a mechanistic conception of the material world), there are no final causes, and thus nothing that inherently “points to” or is “directed at” anything beyond itself; and in that case, there can be no such thing as intentionality; but there is such a thing as intentionality; therefore materialism is not true.
This is an argument for dualism, I should say, at least if one admits that the material world exists in the first place (which, of course, everyone other than a few adherents of idealism would admit), because it implies that there are features of the world other than its material features. The only way to avoid the dualistic consequences (other than opting for eliminativism or idealism) would be to acknowledge that the Aristotelians were right after all, and that final causes are a real feature of material reality. But that would, of course, be to abandon the entire modern mechanistic-cum-materialistic interpretation of science. Nor would it really stave off dualism for long, for it would simply open the door to the Thomistic or hylemorphic (as opposed to Cartesian) version of dualism. But that is a story for another time – a story which, like other details of the argument sketched here, can be found (if I might be forgiven one more shameless plug) in The Last Superstition.
In the previous post in this series, I argued that the “mechanistic” conception of the natural world adopted by the early modern philosophers more or less entails a kind of dualism insofar as its banishment of final causes from the material world effectively makes intentionality necessarily immaterial. Intentionality, of course, is one of two features of the mind to which contemporary philosophers of mind have paid special attention. The other is consciousness, and in particular the “qualia” that are said to make consciousness uniquely difficult to explain in material terms. There is a good reason for this difficulty – indeed, impossibility – and it is the same reason why intentionality is impossible to explain in materialistic terms. It lies in the mechanistic conception of matter itself.
The early modern philosophers and scientists were obsessed with quantification. There were several reasons for this, one of them being their desire to reorient intellectual efforts toward the improvement of life in this world and away from the otherworldliness of the ancients and medievals. This entailed a new emphasis on technology and more generally on the control and exploitation of the natural world in the interests of bettering man’s material condition. Since quantification would facilitate this, those aspects of nature that could be described in purely mathematical terms took on a special importance, and those which could not came to seem, from the point of view of this new, worldly approach to learning, irrelevant at best and a distraction at worst. Thus did final causes, hidden powers, substantial forms and the like go out the window. So too did the qualitative aspects of nature. Colors, odors, tastes, feels, sounds, and the like, at least as understood by common sense, vary from observer to observer – think of old philosophical chestnuts like the room temperature water that feels warm to one hand and cool to the other, colorblindness, and so forth – making them a poor fit for a science looking to make nature subject to human prediction and control. Out the window with them too, then. The physical world would be redefined as comprised of colorless, odorless, tasteless particles in motion; and color, temperature, and the like would be redefined entirely in terms of the quantifiable relations holding between these particles (e.g. heat and cold in terms of molecular motion). What about color, odor, taste, and so forth as common sense understands them? They in turn were redefined as entirely mind-dependent “secondary qualities” (or rather, ideas of secondary qualities), the ancestors of the contemporary philosopher’s concept of qualia. On the view in question, they do not exist in the physical world as it is in itself, but only in our perceptual representation of that world.
It should be obvious, then, how, as with intentionality, the notion that qualia are incapable of materialistic explanation is not some desperate attempt to avoid the implications of modern science, but is rather precisely a consequence of modern science. The mechanistic conception of matter that underlies science (or rather underlies what, since the 17th century, is allowed to count as science) itself entails that qualia (as we call them today) are immaterial or non-physical. Many early modern thinkers – Descartes, Cudworth, and Locke, for example – saw this, which is part of the reason they were dualists. Given the mechanistic conception of matter, these thinkers concluded that “secondary qualities,” “sensory qualities,” “qualia,” or whatever else you want to call them are necessarily immaterial, precisely because matter got (re)defined by the mechanical philosophy by contrast with these qualities.
Some contemporary naturalists – Joseph Levine, Thomas Nagel, and John Searle, for example – have more or less recognized this, acknowledging that there is nothing more to the contemporary materialist’s concept of matter (which derives from the 17th century “mechanical” conception) other than its contrast with the “qualitative” (and intentional) features of our experience of the world. Precisely for this reason, all three of these thinkers have (in their different ways) regarded modern materialism as deeply conceptually problematic, though they have also stopped short of embracing dualism. But other contemporary naturalists – Dennett and the Churchlands, for example, not to mention countless lesser lights of the sort who write crude atheist pamphlets and pop neuroscience books – cluelessly suggest that there is no good reason to think that the mind will fail to yield to the same sort of reductive explanation in terms of which everything else in nature has been accounted for.
In fact there is a very good reason why the mind should be uniquely resistant to such “explanation,” and it precisely because everything that doesn’t fit the mechanistic-cum-quantificational picture of the natural world has not been “explained” by science at all, but simply swept under the rug of the mind and treated as a mere “projection.” This is true in particular of anything in nature that seems to smack of final causality or to have an irreducible qualitative (as opposed to quantitative) character. It is conceptually impossible that the mind itself should be “explained” in the same way – that is to say, by further sweeping – which is why modern philosophy has a “mind-body problem” of a sort that did not exist before the mechanistic revolution, and why all materialist attempts to “explain” the mind are really disguised versions of eliminative materialism. The tiresome canard that “everything else has already been explained in materialistic terms” is thus a gigantic shell game, pure sleight of hand, a complete fraud from start to finish. (This is a theme I first explored in my book Philosophy of Mind and develop at length in The Last Superstition.)
In any case, we have now a third brief argument for dualism, which can be summarized as follows: Given the materialist’s own (mechanistic-cum-quantificational) conception of matter, colors, odors, tastes and the like as we experience them do not exist in the material world itself; but these qualities do exist in our perceptual representations of the material world; therefore, there exist features of the world – namely these sensory qualities or “qualia” that characterize our perceptual experiences – that are not material or physical features.
Obviously this argument raises questions about how these immaterial features relate to the material ones – Are they basic or emergent? How can they causally interact with the material ones? Do they inhere in a physical or a non-physical substance? – but the fact that it raises them has no bearing on the cogency of the argument itself. My own view is that the standard (Cartesian) dualist answers to such questions are problematic precisely because they buy into the same mechanistic conception of matter to which materialists are beholden. The right approach is to challenge that conception of matter, and return to the Aristotelian-Scholastic picture it replaced. But whether I am right about this or not is also irrelevant to the argument just given, which does not assume any Aristotelian-Scholastic premises, but simply draws out the consequences of the very conception of matter to which materialists themselves are committed. Whatever the deficiencies of Cartesian dualism, they do not approach the sheer incoherence and cluelessness of contemporary materialism.
The arguments for dualism considered so far in this series (see here, here, and here) have been more or less “modern” rather than “classical.” They focus on those aspects of the mind most familiar to contemporary philosophers, namely intentionality (the meaningfulness or directedness beyond themselves of thoughts and the like) and qualia (those aspects of a conscious experience which are directly knowable only via introspection, and thus only by the one undergoing the experience). And they contend that, given the mechanistic conception of matter taken for granted by modern philosophers (dualists and materialists alike), these features of the mind are necessarily immaterial.
Classical arguments for the immateriality of the mind, by which I mean the sort common within Western philosophy prior to Descartes and defended by the likes of Plato, Aristotle, and Aquinas, are very different. You won’t find the latter thinkers going on about either qualia or intentionality, because the very notions of qualia and intentionality, as usually understood, are artifacts of the modern mechanistic re-conception of the material world. “Qualia” are what you get when you deny that matter can have anything like the sensible qualities it seems to have in ordinary experience. “Intentionality” is what you get when you insist that the material world is devoid of anything like final causality, when you go on accordingly to relocate all meaning and purpose within the mind, and when you also go on in turn to characterize mental states as internal “representations” of an external reality. I have said a little bit about all of this in earlier posts, and it is a theme I explore in great detail in The Last Superstition.
For Plato, Aristotle, Aquinas, and other ancients and medievals, the main reason why the mind has to be immaterial concerns its affinity to its primary objects of knowledge, namely universals, which are themselves immaterial. When properly fleshed out and understood, this sort of argument is in my view decisive. Yet it has received very little attention from contemporary philosophers, partly, I think, because of their general ignorance of what the ancients and medievals thought, and partly because the logic of the mechanistic revolution inaugurated by Galileo, Descartes, Hobbes, Locke, et al. has pushed them into so cramped and narrow a conceptual space that they can hardly even conceive any alternative to it. The result is that when they do address the arguments of the ancients and medievals (concerning this subject or any other), they almost always distort them in the most grotesque fashion, anachronistically reading into them assumptions that make sense only if one takes for granted conceptions of matter, mind, causation, etc. that the older thinkers in question would have regarded as deeply mistaken and muddleheaded. (Thus is Aristotle made out to be a “functionalist” vis-à-vis the mind, Aquinas’s Fifth Way is read as if it were an anticipation of Paley’s feeble “design argument,” etc.)
In The Last Superstition, I explain at length why some form of realism about universals is rationally unavoidable. (Whether it is the Platonic form of realism, the Aristotelian one, or the Scholastic one that we should endorse is a separate matter irrelevant to present purposes.) I am not going to attempt to summarize that case here, but the examples to follow should suffice to give a sense of how an argument from the reality of universals to the immateriality of the mind might proceed. Readers wanting a fuller treatment should consult TLS.
Consider that when you think about triangularity, as you might when proving a geometrical theorem, it is necessarily perfect triangularity that you are contemplating, not some mere approximation of it. Triangularity as your intellect grasps it is entirely determinate or exact; for example, what you grasp is the notion of a closed plane figure with three perfectly straight sides, rather than that of something which may or may not have straight sides or which may or may not be closed. Of course, your mental image of a triangle might not be exact, but rather indeterminate and fuzzy. But to grasp something with the intellect is not the same as to form a mental image of it. For any mental image of a triangle is necessarily going to be of an isosceles triangle specifically, or of a scalene one, or an equilateral one; but the concept of triangularity that your intellect grasps applies to all triangles alike. Any mental image of a triangle is going to have certain features, such as a particular color, that are no part of the concept of triangularity in general. A mental image is something private and subjective, while the concept of triangularity is objective and grasped by many minds at once. And so forth. In general, to grasp a concept is simply not the same thing as having a mental image. (Again, see TLS for more details.)
Now the thought you are having about triangularity when you grasp it must be as determinate or exact as triangularity itself, otherwise it just wouldn’t be a thought about triangularity in the first place, but only a thought about some approximation of triangularity. Yet material things are never determinate or exact in this way. Any material triangle, for example, is always only ever an approximation of perfect triangularity (since it is bound to have sides that are less than perfectly straight, etc., even if this is undetectable to the naked eye). And in general, material symbols and representations are inherently always to some extent vague, ambiguous, or otherwise inexact, susceptible of various alternative interpretations. It follows, then, that any thought you might have about triangularity is not something material; in particular, it is not some process occurring in the brain. And what goes for triangularity goes for any thought that involves the grasp of a universal, since universals in general (or at least very many of them, in case someone should wish to dispute this) are determinate and exact in a way material objects and processes cannot be.
As James F. Ross has argued, some of the best-known arguments of twentieth-century analytic philosophy reinforce this judgment. For instance, Quine’s arguments for the indeterminacy of translation and Kripke’s argument regarding “quaddition” show that there is in principle nothing in the facts about human behavior or physiology, or in any other physicalistically “respectable” set of facts, that can determine (say) whether by “gavagai” I mean “rabbit” or “undetached rabbit part,” or whether I am doing addition rather than “quaddition.” Indeed, these arguments show that this same indeterminacy afflicts everything I say or do. Yet it is simply false that everything I say or do is indeterminate in this way. For example, should I deploy modus ponens in defending a Quine- or Kripke-style argument, what I will be deploying is indeed modus ponens and not some mere approximation of modus ponens; certainly it had better be modus ponens and not some mere approximation, otherwise my arguments would all be invalid. Nor will it do to suggest that maybe all my arguments really are invalid, for even to deny that I ever really use modus ponens but only ever approximate it requires that I first grasp determinately what modus ponens is before judging that I never really engage in it. Similarly, if someone wanted to deny that we ever really grasp perfect triangularity, he would first have to grasp it himself before going on to judge (obviously falsely, in that case) that it is something we never grasp.
So, there is no coherent sense to be made of the suggestion that all of our thoughts are indeterminate. But if at least some of them are determinate, and no physical process or set of physical facts is ever determinate, it follows that at least some of our thoughts are not physical. (Ross’s argument, by the way, is elegantly developed in his article “Immaterial Aspects of Thought,” which appeared in the Journal of Philosophy in 1992. A later version of this article is available at his website, in the form of a chapter of his book manuscript Hidden Necessities.)
That is one way an argument from realism about universals to the immateriality of the mind can be developed. There are other ways too, which I will summarize in future posts.
Whatever one thinks of arguments like this, it is important to understand that (like the other arguments I’ve presented in this series) they are not the sort that might be undermined by the findings of neuroscience, or any other empirical science for that matter. They are not “soul of the gaps” arguments which purport to give a quasi-scientific explanation of some psychological phenomenon that we simply haven’t got enough empirical data to explain in a materialistic way. Rather, they purport to show that it is in principle impossible, conceptually impossible, for the intellect to be accounted for in a materialistic way. If such arguments work at all, they establish conclusively that the intellect could no more be identified with processes in the brain than two and two could make five. If they are mistaken, they would be mistaken in the way one might make a mistake in attempting to carry out a geometrical proof, and not by virtue of having failed to take account of this or that finding of brain research.
The next argument in our series is inspired by Karl Popper, and in particular by some ideas he first presented in his short article “Language and the Body-Mind Problem” (available in his collection Conjectures and Refutations) and repeated in The Self and Its Brain. As Popper originally formulated it, its immediate aim was to demonstrate the impossibility of a causal theory of linguistic meaning, but it is evident from some remarks he once made about F. A. Hayek’s book The Sensory Order that he also regarded it as a refutation of any causal theory of the mind. (See my essay “Hayek the Cognitive Scientist and Philosopher of Mind” in The Cambridge Companion to Hayek.) Hilary Putnam would later present a similar line of argument in his book Renewing Philosophy, though he does not seem to be aware of Popper’s version.
The argument as I will state it is somewhat different from anything either Popper or Putnam has said, though it is in the same spirit. Before stating the argument, it is worthwhile recalling the “mechanistic” conception of the natural world which, as I have emphasized in earlier posts in this series, implicitly or explicitly informs materialism. On this conception, the world is devoid of what Aristotelians call formal and final causes: there are in nature no substantial forms or inherent powers of the sort affirmed by the medieval Scholastics, and there is no meaning, purpose, or goal-directedness either. The physical world is instead composed entirely of inherently purposeless elements (atoms, corpuscles, quarks, or whatever) governed by inherently meaningless patterns of cause and effect. All the complex phenomena of our experience, from grapes to galaxy clusters, from mudslides to minds, must somehow be explicable in terms of these elements and the causal regularities they exhibit.
But in fact there can be no such explanation of the mind, not even in principle. In particular, there can be no such explanation of intentionality, the mind’s capacity to represent the world beyond itself – as it does, say, when your thought that the cat is on the mat represents the cat’s being on the mat.
The reason is this. As already indicated, any materialistic explanation of intentionality is bound to be a causal explanation. That is to say, it is going to be an attempt to show that the intentionality of a mental state somehow derives from its causal relations. The causal relations in question might be internal to the brain (as they are according to “internalist” theories of meaning); they might extend beyond the brain to objects and events in a person’s environment (as they do according to “externalist” theories); they may even extend backwards in time millions of years to the environment in which our ancestors evolved (as they do according to “biosemantic” theories). An adequate description of the relevant causal relations may require any number of technical qualifications (such as an appeal to Fodor’s notion of “asymmetric dependence”). In every case, though, a materialist is bound to appeal to some pattern of causal relations or other as the key to explaining intentionality. He’s got nothing else to appeal to, after all; the basic elements out of which everything in the physical world is made are by his own admission devoid of any meaning (“intentionality simply doesn’t go that deep,” as Fodor insists in Psychosemantics) and anything other than these elements exists only insofar as causal interactions between the elements generates it.
Now, specifying the relevant causal relation entails specifying a relevant beginning point to the series and a relevant end point. We have to identify some physical phenomenon as that which does the representing, and some other physical phenomenon as that which is represented; or in other words, we have to pick out one thing as the thought, and another thing as that which is thought about. To take a simple example, if we imagine that a certain brain process is associated with the thought that the cat is on the mat because it is caused in such-and-such a way by the presence of cats on mats, then we will have to take the cat’s presence on the mat as the beginning of the relevant causal chain (call it A) and the occurrence of the brain process in question (call it B) as the end. (Of course, specifying exactly what the “such-and-such a way” involves can get pretty complicated, as anyone familiar with the contemporary literature knows, but the complications are irrelevant for our purposes here.)
But what objective reason is there to identify A and B as “the beginning” and “the end” of a causal sequence? Consider what happens in a situation like the one in question. Someone flips on a light switch, which causes electrical current to flow through the wires in the wall up to a ceiling lamp. Light from the lamp travels to a cat sitting on a mat below, is reflected off of the cat, and travels to the retinas of a nearby observer. This in turn causes signals to be sent up the optic nerves to the brain, which results in the firing of a certain cluster of neurons, which in turn results in the firing of another cluster, which in turn results in the firing of yet another cluster, and so on and so forth. All this neural activity ultimately results in a behavioral response, such as walking over to the refrigerator to get the milk bottle out so as to give the cat a snack. And this is followed, say, by an accidental dropping of the milk bottle, which results in broken glass, a cut to the ankle, a yelp of pain, and the kicking of the cat.
Now, again, what is it about this complex chain of events that justifies picking out A and B specifically and labeling them “the beginning” and “the end” respectively? Why is it the cat’s presence on the mat that counts as “the beginning” – rather than, say, the flipping of the light switch, or the flow of the current to the ceiling lamp, or the arrival of such-and-such a photon at exactly the midpoint between the surface of the cat and the observer’s left retina? Why is it brain process B exactly that counts as “the end” of the causal chain – rather than, say, the brain process immediately before B or immediately after B, or the walk over to the refrigerator, or the motion of such-and-such a shard of glass from the broken milk bottle as it skips across the floor? Of course, we have an interest in picking out and identifying cats and not in picking out and identifying individual photons, and an interest in brain processes and their associated mental states that we don’t have in shards of glass. But that is a fact about us, not a fact about the physical world itself. Objectively, as far as the physical world itself is concerned, there is just the ongoing and incredibly complex sequence of causes and effects, which extends indefinitely forward and backward in time well beyond the events we have described. Objectively, that is to say, there is no such thing as “the beginning” or “the end,” and nothing inherently significant about any one event as compared to another.
Popper’s point, and Putnam’s, is that what count as the “beginning” and “end” points of such a causal sequence, and thus what counts as “the causal sequence” itself considered in isolation from the rest of the overall causal situation, are interest relative. These particular aspects of the overall causal situation have no special significance apart from a mind which interprets them as having it. But in that case they cannot coherently be appealed to in order to explain the mind. It is no good saying that the representational character of our mental states derives from their causal relations when the causal relations themselves cannot be specified except in terms of how they are represented by certain mental states. A vicious circularity afflicts any such “theory” of intentionality.
Now it is important to emphasize that the point is not that causation per se is interest relative or mind-dependent; the argument is not an exercise in idealism or anti-realism. The overall complex ongoing sequence of causes and effects is entirely mind-independent. The claim, again, is just that something’s counting as a “beginning” or “end” point within the series is interest-relative and mind-dependent. Still, even this much might seem to be too close to idealism or anti-realism for comfort. It might seem to make causal explanations somehow subjective and arbitrary. (Indeed, Putnam attributes something like this sort of objection to Noam Chomsky.) But to fear that the Popper/Putnam argument we’ve been considering might entail that causal explanations are somehow subjective or arbitrary doesn’t show that the argument is wrong.
Is there any way to reconcile the argument with the objectivity and non-arbitrariness of causal explanations? Absolutely. The way to do it is to show that certain physical phenomena really can objectively count as the beginning or end points of a causal sequence after all – that they can indeed be picked out in a way that is not mind-dependent or interest-relative. But how can that be done? By showing that natural objects and processes are by their natures inherently directed towards the generation of certain other natural objects and processes as an “end” or “goal.” That is to say, by showing that natural objects and processes have what Aristotelians call substantial forms and final causes. In short, the way to explain how causal explanations can be objective and non-arbitrary as opposed to subjective and interest-relative is to acknowledge that the mechanistic conception of the world is mistaken, and that the Aristotelian-Scholastic conception that it replaced is correct after all.
So, the Popper/Putnam argument shows that the mechanistic conception of nature to which materialists are explicitly or implicitly committed entails that there can be no materialistic explanation of the mind. (As we have seen in earlier posts in this series, other arguments tend to show the same thing.) And the only way to sidestep the argument is to abandon the mechanistic conception of nature, which entails rejecting materialism anyway. Either way, materialism is refuted.
What positive view results? That depends. If one holds on to the mechanistic conception of nature, the result would seem to be some broadly Cartesian form of dualism – either substance dualism or property dualism. (Popper himself opted for the former. Putnam does not consider what consequences his view might have for the dualism/materialism debate.) If instead on opts to return to an Aristotelian conception of nature – the right choice, in my view – then one is on the path toward hylemorphic or Thomistic dualism. (I examine these options in my book Philosophy of Mind and defend the latter at length in The Last Superstition.)
Hence, one way or the other dualism is vindicated. And as with the arguments presented in earlier posts in this series, it will not to do object to this one that it somehow “violates Ockham’s razor,” that materialism is the “simpler explanation,” and so forth. Such objections can only have force against attempts to present dualism as a “probable” “hypothesis” “postulated” as the “best explanation” of the “data.” That is not the sort of argument I have given. As I have already said, the argument just presented is an attempt to show that materialism fails in principle; it purports to be a metaphysical demonstration of the falsity of materialism, not a piece of quasi-empirical theorizing. If it fails (and obviously I don’t think it does), it does not fail for the sorts of reasons empirical hypotheses do.