Thomas Nagel, a famous philosopher if there is such a thing in America, has written a book a bold title: Mind and Cosmos: Why the Materialist Neo-Darwinian Conception of Nature Is Almost Certainly False. The main title invites you to settle into your armchair for an evening of speculative meditation; the subtitle orders you to the barricades, in preparation for the coming intellectual revolution. The title as a whole seems to be premised on the good cop, bad cop theory of naming. When you write a book with a title like this, you better be able to deliver.
Nagel doesn’t deliver.
Not only doesn’t Nagel deliver: he strikes out three times, with three distinct arguments as to why we should reject natural selection in its current, materialist form. Each of the book’s three main thrusts – involving consciousness, theoretical knowledge, and morality – begets a unique species of error.
Nagel’s critique of natural selection is in part an extension of an argument that helped establish his reputation, one that most philosophy students will know from his classic 1974 paper, “What is it Like to Be a Bat?” Here he argues that mental states, while caused by brain states, cannot be adequately explained by them. That’s because we can make no inferences from specific brain states to what it is like to have the subjective experiences associated with them, a point well illustrated by the case of echolocation in bats. We’ll never know what it’s like to be bats, no matter how much we can say about bat brains. But science is in the business of such inferences, and Nagel is correct to say that the fact that we cannot make them in this case is a prohibitive challenge to any attempt to explain consciousness by reducing it to matter. We call this the “mind-body problem.”
In Mind and Cosmos, Nagel claims that the failure of a materialist reduction of mind to matter has implications for science in general, including natural selection. Since the brain does not adequately explain consciousness, neither can natural selection, even if it adequately explains the brain. The mind-body problem becomes the mind-evolution problem.
Nagel supplements his argument from consciousness with two others, to the effect that natural selection is incompatible with the possibility of theoretical knowledge and the objectivity of ethical judgments. But he also more generally entertains the notion that natural selection is too implausible to explain much of anything. Nagel finds it “highly implausible that life as we know it is the result of a sequence of physical accidents together with the mechanism of natural selection.” He seems to doubt that there could be enough time in the world or available mutations to produce something as remarkable as a squirrel, much less human beings and consciousness. Nagel realizes that he cannot provide a definitive argument in favor of this general skepticism about the plausibility of natural selection; which is why the bulk of the book is focused on the arguments from consciousness, theoretical knowledge (or “cognition”), and value.
Nagel’s argument from consciousness suggests to him that the problem with natural selection is its materialism. And so his solution is to amend natural selection to incorporate a non-materialist explanation in which mind is a basic feature of the universe. Of a number of non-materialist alternatives, the explanation that Nagel favors is teleological (pan-psychism and monism have certain drawbacks, and Nagel admits to being biased against theism’s appeal to explanations outside of nature). Nagel’s teleological principle works such that the available mutations upon which natural selection operates must be determined in part by a pre-existing tendency of the universe – itself not reducible to physics or chemistry or another other causal explanation afforded by materialist natural science – to produce beings that are capable of consciousness, theoretical knowledge, and objective judgments of value.
In other words, evolution is rigged: not by God, but by some non-material yet natural cause.
To see why Nagel reaches this conclusion, it is important to understand that he is motivated by his search for a workaround to the mind-body problem that saves it from its seeming intractability. Nagel believes natural selection provides him with an opportunity for such a workaround. Along the way, he will assume that the world must be maximally intelligible to us. So when it comes to choosing between admitting to the intractability of the mind-body problem and modifying natural selection with a teleological principle, however strange that might seem, teleology wins the day.
It will help to review the three prongs of Nagel’s argument in more detail. After summarizing them, I offer some criticisms showing how each of these prongs misses its mark.
The mind-body problem is a problem of the contingency of brain-mind causation. This contingency means that knowing everything there is to know about the structure of the brain and the laws of physics and chemistry, it would not be possible to demonstrate that mental states must follow from brain states; or what kinds of mental states follow from what kinds of brain states; or what it is like to have such mental states. We can imagine a world in which brain states do not cause the mental states at all.
Scientists do better in their attempts to explain more obviously physical phenomena, such as water. That’s because water is reducible to the molecule H2O, the structure of which provides a satisfying explanation of why water has the properties it has (water is clear because of the way H2O interacts with light in the visible spectrum). In this case, we have a physical or scientific reduction: water and H2O are identical, and the properties of water are the necessary results of the structure of H2O. Because mental states do not follow necessarily from brain states in the same way, the brain cannot explain consciousness in the satisfying way that H20 explains water.
The upshot of all this is that mind is not scientifically reducible to the brain. Nor is it, according to Nagel, conceptually (or logically) reducible: which is to say, we cannot show that language referring to mental states is reducible to language referring to brain states or behavior. That’s because language referring to mental states tells us what it’s like to have those mental states, and language referring to brain states or behavior does not. (Often, philosophers use conceptual reduction in the service of physical reduction, for example by attempting to explain the identity of mind and brain in terms of a relation between brain states and physical behavior).
For Nagel, natural selection will explain consciousness only if it saves us from the seeming contingency of brain-mind causation. This means that it cannot be the case that the brain just happens to cause consciousness – that this causation is an inexplicable, contingent, brute fact. Consequently, consciousness cannot simply be an accidental evolutionary byproduct of the brain (in the way that the redness of vertebrate blood is the byproduct of the selection of hemoglobin – not for its redness-conferring but for its oxygen transporting properties). For natural selection to explain consciousness, it must show why it was more likely than not to be the result of the evolutionary process.
Teleology saves the day by rigging natural selection to produce beings that are capable of consciousness.
Nagel is also worried that natural selection undermines cognition, or theoretical knowledge in the domains of language, science, logic, and ethics. While there is a clear adaptive value to the accuracy of sense perceptions (and so no need to doubt ordinary perceptual knowledge), there is no adaptive value to theoretical pursuits such as science. And any attempt to argue otherwise, according to Nagel, would be circular: to say that logical judgments have adaptive value, for instance, is to rely on an evolutionary account that itself presupposes the accuracy of logical judgments. Reason must involve a direct access to truths unqualified by whether such truths enhance fitness.
Teleology saves the day be rigging natural selection to produce beings capable of a transcendent grasp of objective reality.
Finally, Nagel is worried that materialist natural selection undermines moral realism, or the view that moral propositions (for example “murder is wrong”) purport to objectively describe the world. This is to say that they fall into the same category as our everyday empirical factual claims (“the cat is on the mat”), and like them are true or false based on what’s going on the in world, not based on the opinions of human beings. In fact, for some moral realists they are true independently of the cognitive constitutions of human beings – of their physiology and psychology and resulting evaluative and motivational dispositions. In this case, the wrongness of murder is independent of the psychological and social forces that generally lead human societies to frown upon murder.
According to Nagel, moral realism is incompatible with natural selection because there is no adaptive value to recognizing evaluative truths. Where the accuracy of our perceptual judgments is critical to survival, the “real badness” of pain irrelevant. Here Nagel relies heavily on Sharon Street’s “A Darwinian Dilemma for Realist Theories of Value,” which argues that natural selection must have a “purely distorting” influence on evaluative judgments in the sense that it selects the evaluative tendencies underlying such judgments based on whether they are adaptive, not on whether their corresponding value judgments are true or false. (You can read my full account of Street’s argument here). Where Street takes this incompatibility of natural selection and moral realism a reason to reject moral realism, Nagel takes it as a reason to reject natural selection in its materialist form, unmodified by teleology (he admits that he is merely assuming here that moral realism is true).
Teleology saves the day be rigging natural selection to produce beings capable of objective ethical judgments.
Nagel’s argument from consciousness gives a helpful overview of the mind-body problem, and it is the most useful part of his book. But his attempt to extend the mind-body problem to natural selection depends on two flawed assumptions. The first is that the world must be comprehensively intelligible to human beings. The second is that intelligibility involves some very idiosyncratic criteria involving probability – namely, that an explanation must show that its explanandum was more likely to occur than not (and relatedly, that consciousness is not an evolutionary byproduct or relatum of a brute fact).
Nagel’s second assumption, regarding probability, is puzzling. Some events are actually improbable, and as Eliot Sober points out in his review of Nagel’s book, something’s being improbable does not make it unintelligible. Genetics explains, in some sense, why a couple might have two daughters, despite its Mendelian probability of 25 percent. It doesn’t tell us that this result was more likely than not – although it does tell us that a certain sexual distribution overall is inevitable. (The same point goes for Nagel’s general sense about the improbability of “life as we know it”: my winning the lottery is unlikely; someone’s winning the lottery is likely; life arising on earth may have been improbable; we can currently say little about the probability of life arising somewhere in the universe after billions of years).
Natural selection explains consciousness in the same way that genetics explains a specific sexual distribution, insofar as it provides a general set of principles applicable to various specific causal sequences. This is a weaker sense of explanation than Nagel would like. He demands that natural selection explain consciousness in some more robust sense – seemingly in one similar to the way in which H2O explains water via a necessary physical identity.
This is not something that natural selection can do, and it is not something we should demand of it or any contingent historical account (Jerry Fodor’s What Darwin Got Wrong seems to rely on the same sort of mistaken demand). Even if the universe is deterministic, and causal chains turn out to be in some sense necessary, that doesn’t give us necessary correlations between types of causes and effects (I happened to stub my toe because I tripped on a tree branch; but there isn’t some universal correlation between tree branches and toe stubbing). Some explanations – like natural selection leading to the development of consciousness – are a matter of contingency. Contingent causal chains cannot do the work of necessary physical identities. Natural selection cannot solve the mind-body problem; nor should we ask it to do so.
But it is Nagel’s first assumption – that the universe is maximally intelligible – that has forced him into the position of making a contingent historical account perform the work of scientific necessity to which it is so unsuited. The world must be maximally intelligible, yet attempts at saying how the brain causes consciousness have gone nowhere. Nagel thinks he has found a workaround, a breach in a different part of the philosophical defenses than those to which philosophers of mind are accustomed to focusing their efforts. If we cannot say directly how the brain causes consciousness, then natural selection perhaps can be made to account.
But the way that Nagel makes natural selection account for consciousness is no more satisfying then our current mind-body predicament. How is teleology more satisfying than a brute, inexplicable relation between brain and mind? Suppose that, like Nagel, we felt compelled to accept teleology. Would we feel any better about the mind-body problem? Any less puzzled? Teleology can tell us nothing about how the brain produces consciousness. Like monism and pan-psychism, it introduces mind as a basic feature of the universe in a way that is interesting and suggestive. But while mind may in fact be a basic feature of the universe and irreducible to matter, it is still the case from the human standpoint that a) mind and matter are related and b) this relation is puzzling. Teleology doesn’t make mind any less puzzling: it merely grandfathers it in to assure us that in some sense it was there all along, from the beginning of time, before there were brains. But by grandfathering in mind, we introduce the problem of its relation to matter at an early historical point and in a different form: how does mind accomplish its ends? How does teleology work? We know even less about the relation between mind in general and the world it is supposed to guide, than we do about the relation between specific minds and specific brains. We can seek a way out of this predicament via idealism (to which Nagel hints that he is sympathetic), in which case world and mind in general are made identical. But it is unclear how this would solve any of these puzzles, which can be reformulated within the idealist framework (how are individual minds and mind in general related?). I happen to agree with Nagel about the irreducibility of consciousness; but I don’t think the concept of teleology makes consciousness any less baffling.
The charge of circularity that Nagel levels in his argument from cognition is based entirely on the kind of misunderstanding that is surprising for a philosopher of his caliber. It is not circular to argue that logical judgments have adaptive value via an evolutionary account that depends on the accuracy of logical judgments. This charge of circularity presupposes that we appeal to an evolutionary account in order to ground the accuracy of logical judgments (that is, that we are setting out to demonstrate their accuracy). In fact, one appeals to the evolutionary account not to ground the accuracy of logical judgments, but merely to show that their accuracy is possible. We assume that logical judgments are accurate (we’re forced to make this assumption – logical judgments cannot be grounded). We appeal to the notion that they are adaptive only to show that their accuracy need not be undermined by their evolutionary origin – to show that they need not be inconsistent with such an explanation.
Nagel’s argument concerning value relies heavily on an argument by Sharon Street to the effect that natural selection and moral realism are incompatible. I have outlined elsewhere why I think that Street’s argument is not as compelling as Nagel thinks it is. But even if we grant that moral realism and natural selection are incompatible, Nagel gives us no reason for choosing moral realism at the expense of natural selection (beyond the flawed case against materialist natural selection that he has made in the previous sections of the book). Why not accept, as Street does, a constructivist account of morality?
A bad book like this, by philosopher with a good name, gives philosophers in general a bad name. Beyond the more fair-minded critiques of Nagel’s book by fellow philosophers, it’s not hard to find intemperate online posts and comments citing this book as a reason to scorn philosophy in general. Such critics cannot articulate precisely what’s wrong with the book, beyond their general conviction that it must involve an ignorance of the sciences typical of the barbarous humanities.
In fact, Nagel’s errors are philosophical and logical, which is why these firebrands are relatively helpless in their attempt to craft a relevant response. Teleology is certainly possible, and Nagel is not wrong to ask us to set aside our materialist presuppositions to consider radical alternatives. But he also needs to provide us with good reasons for believing that such radical alternatives are necessary. Nagel is unconvincing on this score, because it is not clear that the we must amend scientific theories to solve philosophical problems, in such a way as to guarantee the maximal intelligibility of the world; or that intelligibility must be linked to probability; or that an evolutionary origin for cognition is self-undermining; or that moral realism and natural selection are incompatible (and if so, that it is the latter rather than the former that must be amended). These criticisms go regardless of where we stand generally on such issues as naturalism and materialism, or whether we think the natural sciences can be made to answer all of the sorts of questions that we find interesting. Nevertheless, Nagel’s book will unfortunately serve as a source of comfort not only to those who deny evolution for religious reasons (although Nagel himself is not making such a denial); but to members of the cult of scientism, who will wrongly see the flaws of a book like this as a vindication of their views.
– Wes Alwan