The reason does not (as one might suppose) have anything essentially to do with quantum mechanics, of which Schrödinger was one of the fathers. It has rather to do with a relatively simple philosophical point which was first made by the likes of Cudworth and Malebranche and repeated in recent years by writers like Nagel and Swinburne (as noted in the second of the earlier posts linked to above). Two relevant texts are Schrödinger’s essay “On the Peculiarity of the Scientific World-View” (from What is Life? and Other Scientific Essays) and chapter 6 of his Mind and Matter, entitled “The Mystery of the Sensual Qualities” (reprinted in What is Life? with Mind and Matter and Autobiographical Sketches – a more recent volume which does not include the earlier essay).
To summarize what I’ve said at greater length in earlier posts, the philosophical point in question is that the early moderns’ move of redefining matter so that it is devoid of color, odor, taste, sound, and the like as common sense understands them necessarily made these sensory qualities inexplicable in materialistic terms. Hence, if one is going to affirm the existence both of matter (as redefined by the moderns) and of the sensory qualities (or “qualia,” as they have come to be known, relocated from the external world to the internal world of the mind), then it seems one is necessarily committed to mind-body dualism of some sort (whether substance dualism or property dualism). The only way to avoid such dualism is either to reject the existence of matter (as Berkeley did), to reject the existence of the sensory qualities (as eliminativists do explicitly and most other materialists do implicitly), or to reject the mechanistic conception of matter that led to the problem in the first place (as Aristotelians do; though Aristotelianism still leads to a non-Cartesian form of dualism – what David Oderberg calls hylemorphic dualism – for reasons that have nothing to do with sensory qualities or qualia).
To be sure, Schrödinger himself does not explicitly draw an anti-materialist conclusion. He notes merely that what he calls the “objectivation” of matter – the conceptual removal from it of anything that smacks of the personal or of mind (cf. Thomas Nagel’s “objective/subjective” distinction) – makes the mind itself deeply mysterious. This is compatible with views like Colin McGinn’s “mysterianism” or Joseph Levine’s “explanatory gap” position, which affirm materialism even as they deny that we can understand, or at least (in Levine’s case) that we do in fact understand, how materialism can be true. Not that Schrödinger himself affirms this kind of view either; he simply calls attention to the problem raised by the modern conception of matter without trying to resolve it. (For my part, I consider McGinn’s and Levine’s positions non-starters. You might as well say, in response to Gödel, “Maybe the consistency of a formal system containing computable arithmetic really is internally provable after all, and our minds are just constitutionally incapable of seeing how.”)
Schrödinger’s emphasis is also less on the mind-body problem per se than on the epistemological paradox he sees implied by the modern “objectivation” of matter. As he puts it in “On the Peculiarity of the Scientific World-View”:
We are thus facing the following strange situation. While all building stones for the [modern scientific] world-picture are furnished by the senses qua organs of the mind, while the world picture itself is and remains for everyone a construct of his mind and apart from it has no demonstrable existence, the mind itself remains a stranger in this picture, it has no place in it, it can nowhere be found in it. (p. 216)
That is to say, the picture modern science (as informed by an “objectified” mechanistic conception of matter) paints of the natural world presents it as devoid of the sensory qualities and of anything personal. And yet the picture itself exists only within the minds of persons – scientists themselves – and takes as its evidential base the senses, and thus the very sensory qualities it refuses to locate in nature.
This epistemological paradox was a major theme of E. A. Burtt’s The Metaphysical Foundations of Modern Physical Science (Burtt being, as I have noted before, one of several major early twentieth-century scholars who emphasized the problematic character of the mechanistic revolution, before this theme went down the academic memory hole sometime in the 1960s). But awareness of it goes back much farther than that – indeed (and as Schrödinger reminds us) all the way back to the 5th century B.C., and in particular to Democritus, one of the fathers of atomism. In a famous fragment, Democritus imagines a conversation between the intellect, which (as Democritus naturally assumed) must endorse the atomists’ banishment of the sensory qualities from nature, and the senses, which form the evidential basis for the atomist theory:
Intellect: “Color is by convention, sweet by convention, bitter by convention; in truth there are but atoms and the void.”
Senses: “Wretched mind, from us you are taking the evidence by which you would overthrow us? Your victory is your own fall.”
It must be emphasized that Democritus is, commendably, calling attention to a difficulty facing a theory that he himself endorses; and that we have no idea how, or even if, he tried to resolve it. It is by no means obvious that any materialist in the intervening millennia has done any better. Many of them have done worse; indeed, vulgar materialists of the New Atheist stripe typically show no awareness that there is a problem here in the first place. Unfortunately, this includes Daniel Dennett, a well-known philosopher of mind. Dennett explicitly endorses an eliminativist position vis-à-vis the sensory qualities (see e.g. his essay “Quining Qualia”) – which is to his credit insofar as (I would argue) any consistent materialist must ultimately be an eliminativist anyway. What is not to his credit is his utter blindness to the deep philosophical puzzles such a position opens up, his peddling of shameless caricatures of anti-materialist views, and in general his refusal to concede that opponents of materialism are motivated by serious philosophical concerns.
Schrödinger provides us with a plausible account of the origins of this sort of blindness (in scientists, anyway – philosophers like Dennett should know better). In “The Mystery of the Sensual Qualities” he writes:
Scientific theories serve to facilitate the survey of our observations and experimental findings. Every scientist knows how difficult it is to remember a moderately extended group of facts, before at least some primitive theoretical picture about them has been shaped. It is therefore small wonder, and by no means to be blamed on the authors of original papers or of text-books, that after a reasonably coherent theory has been formed, they do not describe the bare facts they have found or wish to convey to the reader, but clothe them in the terminology of that theory or theories. This procedure, while very useful for our remembering the facts in a well-ordered pattern, tends to obliterate the distinction between the actual observations and the theory arisen from them. And since the former always are of some sensual quality, theories are easily thought to account for sensual qualities; which, of course, they never do. (p. 164)
In the case at hand, neuroscientists who begin, as every empirical scientist must, with observations – that is to say, with conscious experiences whose character is determined by various sorts of qualia or sensory qualities – go on to construct a theoretical description of the physical and neural processes associated with perception. This theoretical description then takes on, as it were, a life of its own, coming to seem as real or even more real than the concrete experiences that led to it, and the language in which the former is couched comes to be applied to the theorist’s description of the latter. Thus an explanation of “heat” in the sense of molecular motion comes to seem, especially when coupled with neuroscientific data, an explanation of “heat” in the sense of a certain kind of tactile sensory quality; an explanation of “red” in the sense of light of a certain wavelength comes to seem an explanation of “red” in the sense of a certain kind of visual sensory quality; and so forth.
But this is a muddle, a subtle committing of the fallacy of equivocation. The key theoretical concepts – molecular motion, light wavelengths, neural firing patterns, and so forth – are always understood in light of a broadly mechanistic conception of the natural world which follows the early moderns’ project of excluding final causes, sensory qualities and the like from matter and redefining it in abstract mathematical terms. To “explain” sensory qualities or qualia in such “scientific” (i.e. mechanistic and “objectified”) terms is thus really to change the subject. Earlier generations of philosophers and scientists realized this, which is why few of them were materialists – they saw that, by definition as it were, sensory qualities could not be “material” given the new conception of matter. But later generations – especially the current generation of scientists, who tend to be far more specialized and often seem less philosophically-minded or philosophically-educated than their predecessors – have forgotten this conceptual history. And this forgetfulness and philosophical shallowness together with the practical successes of modern science have hardened many of them – or at least the more vocal of the pop science writers among them – into a crude scientism which assumes that there are no philosophical problems, or at least no serious ones, which science is not capable of answering.
Thus, when philosophers come along – whether dualists or the more sophisticated and fair-minded sort of naturalist (e.g. a Searle, a Nagel, or a Chalmers) – and point out that existing neuroscientific “explanations” of consciousness and the like do not in fact explain the relevant phenomena at all, it comes to seem like these philosophers are inventing a new problem in a desperate and obscurantist attempt to salvage a belief in human dignity and specialness. In fact they are simply calling attention to a very old problem that the mechanistic theoretical model itself has created, and of which earlier generations of philosophers and scientists were well aware. In fact it is scientism which fosters obscurantism, ignoring as it does clear conceptual distinctions and forcing all intellectual life into a methodological procrustean bed. And in fact the mechanistic “objectified” conception of matter inherited from the early moderns is not a scientific discovery at all but a philosophical posit, and one which creates philosophical problems rather than solves them.
Obviously I am not claiming to establish these large claims here. (Doing so is in large part what The Last Superstition is about.) And obviously there are different moves a materialist might try to make in order to get around the problems in question (though, equally obviously, I don’t myself think any such moves can succeed). The point is that the problems are real ones, and serious ones. Any naturalist who dismisses them as motivated by irrational religious fanaticism is either ignorant or dishonest; certainly Democritus, Schrödinger, Burtt, Searle, Nagel, Chalmers et al. have no theological ax to grind. It goes without saying that our knowledge of the human brain has come a very long way since the 5th century B.C. But philosophically speaking, the history of materialism from Democritus to Dennett marks a precipitous decline.
Addendum 9/14: It occurs to me on re-reading the post that the Chalmers reference in the first sentence of the second-to-last paragraph is, coupled with the “or,” unintentionally misleading: Chalmers is a naturalist, but he is also a dualist of sorts. My apologies. The conceptual lay of the land vis-à-vis this subject is extremely complex, the range of possible positions is very large, and it is difficult briefly to summarize the issues without oversimplification – especially when (as was the case with this post) one is writing late on a Saturday night!