Do You Only Have a Brain? On Thomas Nagel
Thomas Nagel, a professor of philosophy and of law at New York University, has made his reputation over the last fifty years as a leading contributor to moral and political philosophy, with occasional forays into the philosophy of mind. Most famously, and most relevant to his new book, Mind and Cosmos, he wrote an influential paper in the 1970s with the memorable title “What Is It Like to Be a Bat?” Nagel tried to demonstrate the implausibility of the notion that, even if one knew all the relevant physical facts about the brains of bats, one could have any idea what it felt like to be a bat. How could the subjective feeling of this experience be captured by a set of cold, objective biological and chemical facts about neurons? Nagel’s new book revisits some of these ideas and aims to “develop the rival alternative conceptions” to what he calls the “materialism and Darwinism” of our age.
Nagel’s is the latest in what has become a small cottage industry involving a handful of prominent senior philosophers expressing skepticism about aspects of Darwin’s theory of evolution by natural selection. Some, like the overtly Christian philosopher Alvin Plantinga, have made a career of dialectical ingenuity in support of the rationality of religious faith. Others, such as Jerry Fodor, are avowed atheists like Nagel, and have only tried to raise challenges to discrete aspects of evolutionary explanations for biological phenomena. Plantinga’s influence has largely been limited to other religious believers, while Fodor’s challenge was exposed rather quickly by philosophers as trading on confusions (even Nagel disowns it in a footnote). Nagel now enters the fray with a far-reaching broadside against Darwin and materialism worthy of the true-believing Plantinga (whom Nagel cites favorably). We suspect that philosophers—even philosophers sympathetic to some of Nagel’s concerns—will be disappointed by the actual quality of the argument.
Nagel opposes two main components of the “materialist” view inspired by Darwin’s theory of evolution by natural selection. The first is what we will call theoretical reductionism, the view that there is an order of priority among the sciences, with all theories ultimately derivable from physics and all phenomena ultimately explicable in physical terms. We believe, along with most philosophers, that Nagel is right to reject theoretical reductionism, because the sciences have not progressed in a way consistent with it. We have not witnessed the reduction of psychology to biology, biology to chemistry, and chemistry to physics, but rather the proliferation of fields like neuroscience and evolutionary biology that explain psychological and biological phenomena in terms unrecognizable by physics. As the philosopher of biology Philip Kitcher pointed out some thirty years ago, even classical genetics has not been fully reduced to molecular genetics, and that reduction would have been wholly within one field. We simply do not see any serious attempts to reduce all the “higher” sciences to the laws of physics.
Yet Nagel argues in his book as if this kind of reductive materialism really were driving the scientific community. The only named target is the Nobel Prize–winning physicist Steven Weinberg, famous for his defense of the primacy of physics in such popular works as Dreams of a Final Theory (1992). Here is what Nagel writes in describing Weinberg’s view:
My target is a comprehensive, speculative world picture that is reached by extrapolation from some of the discoveries of biology, chemistry, and physics—a particular naturalistic Weltanschauung that postulates a hierarchical relation among the subjects of those sciences, and the completeness in principle of an explanation of everything in the universe through their unification. Such a world view is not a necessary condition of the practice of any of those sciences, and its acceptance or nonacceptance would have no effect on most scientific research.
Nagel here aligns himself, as best we can tell, with the majority view among both philosophers and practicing scientists. Just to take one obvious example, very little of the actual work in biology inspired by Darwin depends on reductive materialism of this sort; evolutionary explanations do not typically appeal to Newton’s laws or general relativity. Given this general consensus (the rhetoric of some popular science writing by Weinberg and others aside), it is puzzling that Nagel thinks he needs to bother attacking theoretical reductionism.
The second component of the thesis Nagel opposes is what we will call naturalism, the view that features of our world—including “consciousness, intentionality, meaning, purpose, thought, and value”—can ultimately be accounted for in terms of the natural processes described by the various sciences (whether or not they are ever “reduced” to physics). Nagel’s arguments here are aimed at a more substantial target, although he gives us few specifics about the kind of naturalism he opposes. He does characterize it as the attempt to explain everything “at the most basic level by the physical sciences, extended to include biology,” and the one named proponent of this view is the philosopher Daniel Dennett. Although Dennett would not characterize his project as trying to explain everything at the “most basic level,” he does aim to show that phenomena such as consciousness, purpose and thought find a natural home in a picture of human beings inspired by Darwin. In the absence of any clearer statement of the argument, we will assume that this is the so-called “neo-Darwinian” picture that Nagel opposes.
Naturalists, including Dennett, defend their view by appealing to the extraordinary fruitfulness of past scientific work, including work growing out of Darwin’s theory of evolution by natural selection. So what should we make of the actual work in biology that supports the “materialist Neo-Darwinian conception of nature” that Nagel thinks “is almost certainly false”? Defending such a sweeping claim might seem to require a detailed engagement with the relevant science, yet in a striking admission early on, Nagel reveals that his book “is just the opinion of a layman who reads widely in the literature that explains contemporary science to the nonspecialist.” And a recurring objection to what he learned from his layman’s reading of popular science writing is that much science “flies in the face of common sense,” that it is inconsistent with “evident facts about ourselves, that it “require[s] us to deny the obvious,” and so on.
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