Thursday, March 21, 2013
Nagel and his critics, Part VII
Let’s return to our look at the critics of Thomas Nagel’s Mind and Cosmos. New commentary on Nagel’s book continues to appear, and to some extent it repeats points made by earlier reviewers I’ve already responded to. Here I want to say something about Mohan Matthen’s review in The Philosophers Magazine. In particular, I want to address what Matthen says about the issue of whether conscious awareness could arise in a purely material cosmos. (Matthen has also commented on Nagel’s book over at the New APPS blog, e.g. here.)
Origins of the mind-body problem
First some stage-setting is in order. In Mind and Cosmos, Nagel writes:
Consciousness is the most conspicuous obstacle to a comprehensive naturalism that relies only on the resources of physical science. The existence of consciousness seems to imply that the physical description of the universe, in spite of its richness and explanatory power, is only part of the truth, and that the natural order is far less austere than it would be if physics and chemistry accounted for everything. If we take this problem seriously, and follow out its implications, it threatens to unravel the entire naturalistic world picture. (p. 35)
Now some of Nagel’s critics agree with him that consciousness poses a serious philosophical puzzle, even if they think its consequences are less dire for materialism than Nagel supposes. H. Allen Orr allows as much in his review in The New York Review of Books, and we saw in an earlier post that Alva Noë does so too in his own remarks on Nagel. But some naturalists are bound to think Nagel must surely be massively overstating things. For science (so the naturalist supposes) has by now explained pretty much everything else; how could consciousness, which has existed only for a relatively short time and in only a relatively tiny percentage of the universe, possibly be a holdout, much less something which “threatens to unravel the entire naturalistic world picture”?
This attitude -- which, I hasten to add, is not one Matthen himself expresses in his review -- is, I think, very common, but it is grounded in an illusion. To see the fallacy, consider an analogy I’ve used many times before. Suppose someone is cleaning the house and carefully sweeps the dirt out of each room into a certain hallway, where he then proceeds to sweep the various piles of dirt he’s created under a certain rug. You tell him that that’s all well and good, but that he has still failed to get rid of the dirt under the rug itself and cannot do so using the same method. He replies:
Are you kidding? The “sweep it under the rug” method is one long success story, having worked everywhere else. How plausible is it that this one little rug in this one little hallway would be the only holdout? Obviously it’s just a matter of time before it yields to the same method. If you think otherwise you’re just flying in the face of the facts -- and, I might add, the consensus of the community of sweepers. Evidently you’ve got some sentimental attachment to this rug and desperately want to think that it is special somehow. Or is it some superstitious religious dogma you’re trying to salvage? What do you think it is, a magic carpet?
The sweeper thinks his critic is delusional, but of course he is himself the delusional one. For the dirt under the rug is obviously the one pile which the “sweep it under the rug” method cannot possibly get rid of, and indeed the more successful that method is elsewhere, the more problematic the particular pile under the rug becomes. The sweeper’s method cannot solve the “dirt under the rug problem” precisely because that method is the source of the problem -- the problem is the price the method’s user must pay for the success it achieves elsewhere.
Now this delusion is exactly parallel to one to which many naturalists are prone. As Nagel writes in Mind and Cosmos:
The modern mind-body problem arose out of the scientific revolution of the seventeenth century, as a direct result of the concept of objective physical reality that drove that revolution. Galileo and Descartes made the crucial conceptual division by proposing that physical science should provide a mathematically precise quantitative description of an external reality extended in space and time, a description limited to spatiotemporal primary qualities such as shape, size, and motion, and to laws governing the relations among them. Subjective appearances, on the other hand -- how this physical world appears to human perception -- were assigned to the mind, and the secondary qualities like color, sound, and smell were to be analyzed relationally, in terms of the power of physical things, acting on the senses, to produce those appearances in the minds of observers. It was essential to leave out or subtract subjective appearances and the human mind -- as well as human intentions and purposes -- from the physical world in order to permit this powerful but austere spatiotemporal conception of objective physical reality to develop. (pp. 35-36)
This is a theme in Nagel’s work that goes back to his famous 1974 article “What Is It Like to Be a Bat?”, and as I have emphasized in earlier posts in this series, it is crucial to understanding what he says in the new book. Human beings are like the hallway in my example, and the human mind is like the rug. The “mathematically precise quantitative description” of the natural world provided by modern science has been as successful as it has been only because those aspects of the natural world that don’t fit that method -- irreducibly qualitative features like color, sound, etc. as they appear to us (as contrasted with scientific redefinitions of color, sound, etc. in terms of such quantifiable features as surface reflectance properties, compression waves, and the like); and final causes, teleology, or purposes -- were swept under the rug of the mind, re-characterized as purely “subjective,” as mere projections that only seem to be features of the external world but are really only aspects of our perceptual representation of it.
As Nagel says, it was precisely this methodological revolution that created the mind-body problem, just as the “sweep it under the rug” method in my example creates a “dirt under the rug problem.” If you essentially define the physical in such a way that it excludes color, sound, purpose, etc. as they appear to us in ordinary experience, and define the mental in such a way that it is the repository of these qualities you have removed from the physical world, then you have carved up the conceptual territory in a way that rules out from the get-go an explanation of the mental in terms of the physical. Far from constituting a desperate resistance to the implications of the scientific revolution, dualism of this essentially Cartesian sort was a consequence of that revolution. (And again, color, sound, etc. as they appear to us are to be distinguished from color, sound, etc. as redefined by physics -- though they are sometimes conflated by sloppier naturalists.)
Early modern thinkers like Cudworth and Malebranche made of this new conception of the physical an explicit argument for dualism, and more recent dualists like Richard Swinburne have done the same. Naturalists like Nagel, John Searle, and Alva Noë do not endorse dualism, but they do see that the methodological revolution in question is the source of the mind-body problem, and thus can hardly in any obvious way provide a solution to it. It is the height of philosophical and historical superficiality to suppose otherwise.
Matthen’s misreading of Nagel
Now I am certainly not accusing Matthen of philosophical or historical superficiality; on the contrary, he is a formidable philosopher of perception and scholar of Aristotle. But his remarks about Nagel’s position vis-à-vis the origin of consciousness oddly take no account of the roots of the mind-body problem in the moderns’ conception of matter -- even though this has for almost forty years been a central theme of Nagel’s work on consciousness, and one revisited in the new book. (In this respect Matthen’s critique of Nagel’s suffers from the same weakness as that of Leiter and Weisberg, which I discussed in an earlier post in this series.)
Matthen instead summarizes Nagel’s position as follows:
Nagel’s reasons for thinking that Darwinism is incomplete with respect to consciousness are summarised in an argument he gives in chapter three. Suppose we knew (a) why all organisms of material constitution M are conscious and (b) how M-constituted organisms emerged by “purely physical evolution”. (a) and (b) might seem together to imply that we know how and why consciousness evolved, but Nagel thinks they do not.
For though (b) explains event types involving material constitution M, we still lack an explanation of event types involving consciousness. To understand the latter, Nagel claims, we need to know why evolution produced consciousness. Such an explanation must make it “likely” that evolution produced conscious organisms under the description “conscious”, and not merely under the description “M-constituted”. There must be such an explanation, he says, since “organisms such as ourselves do not just happen to be conscious”.
Nagel does not contest the possibility of knowing (a) and (b). (a) is a non-historical reduction of consciousness to material constitution; (b) is an evolutionary account of the emergence of the material properties underlying consciousness. Nagel’s central contention is rather that (a) and (b) together do not suffice to make the emergence of consciousness non-accidental.
End quote. Matthen goes on to stress that Nagel’s objection to Darwinian accounts of consciousness is not that the concepts we apply in psychology are different from those we apply in physics; on the contrary, Matthen notes, Nagel says that he “suspect[s] that the appearance of contingency in the relation between mind and brain is probably an illusion, and that it is in fact a necessary but nonconceptual connection, concealed from us by the inadequacy of our present concepts” (Mind and Cosmos, pp. 41-42). Matthen also suggests that even if “evolutionary theory does not make it probable that conscious creatures will emerge,” it is still perfectly reasonable to “hope… that a material account can be given for each realisation of consciousness” and notes that “neuroscientists are certainly hard at work trying to figure out how particular conscious processes are physically realised in humans and other species.”
Given all this, Matthen wonders what the big deal is supposed to be:
[E]ven if there are grounds for pessimism about understanding the emergence of consciousness-as-such in Darwinian terms, this pessimism arises from the fragmentary nature of science and the unavailability of boundary-crossing definitions of consciousness, and not from the exclusion of any material factor.
If I understand him correctly, Matthen seems to think that Nagel’s position really boils down to a complaint that the most we can ever justify is token physicalism rather than type physicalism, coupled with a complaint that what we know about the state of the material universe prior to the existence of consciousness does not make it probable that consciousness would emerge via mutation and natural selection. And this, Matthen thinks (again, if I understand him correctly), is not the sort of thing that should worry any materialist. For it is sufficient for the truth of materialism if each individual token conscious state is realized in some individual token material state or other, even if -- given the differences between the concepts we apply in psychology and those we apply in physical science -- we cannot match up types of conscious states and types of material states. (Cf. Donald Davidson.) And our inability to tell any detailed story about how consciousness emerged via mutation and natural selection is in no way surprising given the contingencies of natural history and the necessarily fragmentary nature of our knowledge of the relevant facts.
Now if all Nagel is saying is what Matthen attributes to him, then Matthen would be right that it does not constitute a serious challenge to materialism. But it is not what Nagel is saying. To be sure, Matthen is correct when he says that Nagel’s complaint is not merely that psychological concepts and physical concepts are different, and he is right to note that Nagel thinks that there may in fact be a necessary connection between mind and brain that is masked by our present concepts. But that is not because Nagel is open to any kind of token physicalism or otherwise thinks materialism gives us at least a partial explanation of consciousness. On the contrary, Nagel’s view is that the concepts of mind and matter that have come down to us from the scientific revolution are not merely different -- as the concept of the morning star is different from the concept of the evening star, even though they apply to the same thing (i.e. Venus) -- but that they positively exclude each other, so that what is “mental” in the sense in question cannot be “physical” in the sense in question. Of the various brands of materialism, Nagel writes:
[A]ll such strategies are unsatisfactory for the same old reason: even with the brain added to the picture, they clearly leave out something essential, without which there would be no mind. And what they leave out is just what deliberately left out of the physical world by Descartes and Galileo in order to form the modern concept of the physical, namely, subjective appearances. (p. 40)
It is only given a “major conceptual revolution” that will issue in “new concepts” (p. 42), and in particular some new, non-physicalist, non-materialist conception of the physical, that Nagel thinks the mental and the physical may turn out to be necessarily connected. Indeed, Nagel holds that “materialism is incomplete even as a theory of the physical world” (p. 45), so that “the usual view of evolution must be revised” insofar as “it is not just a physical process” in the usual sense but must include features to be described by some new “general psychophysical theory” (p. 50). Such a theory might explain our conscious states in terms of our elementary constituents, but only if “the elementary constituents of which we are composed are not merely physical,” as the physical is understood in physical science (p. 54). This new view of matter would not be materialist, but perhaps instead closer to a position like neutral monism or even panpsychism (p. 57).
Matthen’s characterization of Nagel’s position is thus highly misleading, for Nagel is not conceding nearly as much as Matthen seems to think he is. As we have seen, Matthen claims that “Nagel does not contest the possibility of knowing… (a) why all organisms of material constitution M are conscious and (b) how M-constituted organisms emerged by ‘purely physical evolution.’” But it is only given a radically novel conception of the physical, and not the materialist’s conception of the physical, that Nagel thinks we might know (a) and (b). Nagel is not saying: “Yes, I acknowledge that the materialist neo-Darwinian position that is my target can at least account for why organisms of material constitution M (where M is understood in the usual materialist way) are conscious, and that it can account for how M-constituted organisms emerged by purely physical evolution (where “physical” is understood in the usual materialist way). It’s just that I think that more than even that is needed for a complete explanation.”
On the contrary, Nagel compares the supposition that materialist neo-Darwinism can account for consciousness to the obviously fallacious supposition that to explain the physical means by which a calculator displays the symbol “8” when the symbols “3 + 5 =” are tapped into it is sufficient all by itself to explain why what it does counts as arithmetic (pp. 51-52). A description of the purely physical features of the calculator can account only for the symbols considered as mere physical marks, and not for their content. For an explanation of the latter, we need to go outside the purely physical facts to the intentions of the calculator’s designer. Similarly, the “physical” facts as the materialist conceives of them cannot possibly account for consciousness precisely because the conception of the physical the materialist has inherited from early modern thinkers like Galileo, Descartes, and Co. has defined the mental out of the physical, making the physical as devoid of mental features as the symbols on the screen of a calculator are devoid of any inherent, non-derived arithmetical content. You will never get even a partial explanation of the arithmetical content, specifically, of the symbols displayed by a pocket calculator by doing physics alone and ignoring the intentions of designers and users. Neither, in Nagel’s view, will you get anywhere close to an explanation of consciousness if you confine yourself to the physical as the physical is understood by materialists (as opposed to the various conceptions defended by neutral monists, panpsychists, Aristotelians, and others).
Matthen, in short, has simply missed Nagel’s point, and missed it badly, or so it seems to me. And he has missed it because like some other reviewers he has failed to read Nagel’s new book in light of the themes on the topic of consciousness for which Nagel is best known -- this despite the fact that Nagel summarizes those themes in the very chapter Matthen focuses on in his review.
In general it is quite remarkable how little attention some of Nagel’s reviewers pay to the actual details of the book. Someone who has only read the reviews might come away with the false impression that Mind and Cosmos is fundamentally a book about biology (about which Nagel is by his own admission no expert), that his main claim is that the materialist neo-Darwinian account of consciousness and other phenomena is improbable, and that this claim is grounded in common sense intuitions. In fact it is fundamentally a book about metaphysics (about which Nagel is an expert), it argues that a materialist neo-Darwinian account of consciousness and some other phenomena is impossible in principle, and the arguments in question are grounded not in mere intuitions but in a philosophically rigorous and historically informed analysis that Nagel has been developing for decades (and which is only briefly summarized in the book). Nagel does think the arguments support some common sense intuitions, but that is different from resting on a mere appeal to such intuitions. That common sense is right in the relevant respects is a consequence of his arguments, not the foundation of his arguments.
In Matthen’s case I do not attribute his misunderstanding of Nagel’s position to ill will or dishonesty, for his review is substantive and non-polemical. Elliott Sober acknowledged in his review of Nagel (to which I responded here) that his own “reactions may be mired in presuppositions that Nagel is trying to transcend.” It seems to me that that is what might be happening here -- Matthen is reading into Nagel a less radical challenge to materialism than is really there, and thus (unsurprisingly) finds it less challenging than it really is.