Having finally read Nagel's Mind and Cosmos -- previously discussed briefly here -- I had planned to write a more thorough and complete analysis of it. Other more important duties have precluded that goal. So instead, I plan to write a few shorter articles covering various problems in Nagel's philosophy. Here, belatedly, is my first installment of the promised analysis.
Nagel's motivation for his philosophy of neutral monism is that material monism provides no basis for key characteristics of human experience, such as mind and consciousness. With this correct assessment, Christian theists will agree -- although we extend the list of features to include invariant abstract objects (such as mathematics and logic) and absolute moral laws. (Nagel's version of neutral monism1 provides no metaphysical foundation for these either.)
Nagel rejects, therefore, materialism but he equally rejects theism. He wants to invent a "middle ground;" though he doesn't get near a putative "middle." Instead, what he posits is just a new version of attributive monism in which all "matter" (with its many usual physical attributes such as mass, charge, spin and so on) is also endowed with mental attributes. This is just as reductionistic as old-fashioned monism. It's a monism differing in degree, not kind.
Nagel asserts that dualism is not a serious option since it posits an inscrutable and a mysterious (at least more so to "naturalists") interaction between mind and body. To this end, then, Nagel resorts to postulating that all material of the cosmos has a property of mind attached. Every piece of stuff in the cosmos is intrinsically "mental" in some sense, in addition to being material.
This theory is tantamount to adding (in physicist terminology) a "psychic" quantum number to every quantum field. Of course such a psychic interaction has never been observed in particle-scattering experiments. Also, Nagel doesn't touch the issue of the quantity of psychic stuff attached to all matter. To be compatible with quantum field theory, there is a multitude of technical and mathematical issues that Nagel doesn't even begin to address. I won't delve into this in anymore detail at this point, but that alone deprives Nagel's theory of any shred of scientific credibility.
Nagel, by mere verbal wishful thinking, expands on his "solution." Nagel postulates that though each particle is not conscious, one can hope to produce conscious brains by assembling enough of this psychically endowed stuff in sufficiently complex arrangements. A major defect of this theory is that the "mind" so produced is a composite of psychically endowed fields, and as such, still subject to bottom-up causation. All of the properties and "twitching" of this composite brain are the result of the interactions of the basic fields/particles. Such a mind is still physically determined. Thus, human rational freedom still does not exist. Such a theory is thereby a contradiction of most atheists' assumption of human autonomy. One can easily write the form of the equation that such a brain, and consequently the attached "mind," must satisfy. One does not need to know the exact details of the functional dependence of this composite mind on its constituents to draw the conclusion that such a brain is causally closed with respect to the underlying matter. Such an "emergent" mind is to the brain as pressure is to molecular motion - and, thus, has no causal autonomy. Case closed.
These, in brief, are some of the problems with Nagel's philosophy, but in a following blog I will look at the contradictory nature of Nagel's superficial rejection of dualism and proposing neutral monism. Nagel's principle, mentioned above, is that dualism is too mysterious and "unexplained" and that monism (and in particular his neutral monism that purports to explain "mind" and mental interactions) is not mysterious. But is it? Hardly. For a hint at what is coming, some might want to ask the question regarding the graphics below: "What exactly is going on at this electron-photon interaction?" (The straight red line is an electron of charge "e" and the black wavy line is an emitted (or absorbed) photon. The diagram represents the fundamental interaction of electrons and light.)
1 Neutral monism asserts that the ultimate constituents of reality are neither material (as in material monism) nor mental (as in idealism) but a neutral third kind of "stuff." For more details see Neutral Monism at Stanford Encyclopedia of Philosophy.