A redated post.
C. S. Lewis wrote:
Thus no thoroughgoing Naturalist believes in free will: for free will would mean that human beings have the power of independent action, the power of doing something more or other than what was involved by the total series of events. And any such separate power of originating events is what the naturalist denies. Spontaneity, originality, action “on its own” is a privilege reserved for “the whole show” which he calls Nature.
The reason Lewis seems to be offering for saying that the Naturalist must deny free will doesn’t seem to mainly be that if Naturalism were true, determinism would be true, but he seems rather to be saying that free will involves a kind of independent agency on the part of persons that would be proscribed given naturalism.
In a footnote, John Beversluis replies as follows:
Some contemporary naturalists, for example, Daniel Dennett, John Searle, Jaegwon Kim, and Keith Parsons, reject determinism not only on the level of microparticles but generally and argue that naturalism is compatible with believing that human beings have free will.
I am not sure about these philosophers, and what kind of free will these people believe in. Students of the free will question know that there are two conceptions of free will: a conception compatible with determinism, and a concept that is incompatible with determinism. Daniel Dennett wrote an entire book, Elbow Room: The Varieties of Free Will Worth Wanting, which is well known as a classic defense of the compatibilism.
Eventually, I would like to consider the question of whether a thoroughgoing naturalism is compatible with the incompatibilist or libertarian conception of free will. For the purposes of this discussion, however, I want to concede, for the sake of argument, that compatibilism is true, and I will try to show that it is far from clear that a thoroughgoing naturalism is really compatible with free will.
Compatibilist theories of free will trade on the idea that even if determinism is true, the proximate cause of an action can be one’s desire to perform the action. A compatibilist or soft determinist will say emphasize the fact that if you did something, if it is free in the compatibilist sense, you did what you wanted to do. If, say, you robbed the local Bank of America branch, it is not likely to be true that you wanted to be a law-abiding citizen, but the fickle finger of fate grabbed you by the scruff of the neck and made you commit a crime. No, you robbed the bank because, in the words of Willie Sutton, “That’s where the money is."
But notice what is implied in these kinds of theories. First, in order for this theory to be true, desires have to exist. There are naturalistic theories of mind, eliminativist theories, according to which desires are the posits of “folk psychology” and do not in fact exist. Now eliminativists do maintain that a matured neuroscience will replace the terms of folk psychology with successors, but will can the compatibilist theory be fitted in with a successor? Have eliminativists even addressed this issue?
But suppose we accept the existence of desires. In order for the compatibilist theories to work, the desires have to be causally efficacious. It must be the case that my desire for X can cause my action in pursuit of X. But, of course, naturalistic theories of mind, given their commitment to the causal closure of the physical, inevitably face the specter of epiphenomenalism. That is, even if it is thought that beliefs and desires exist on the hypothesis of naturalism, (which, as I have indicated in a previous post, typically involves a commitment to a causally closed mental-free realm and the bottom of everything), how can it be that my desire can cause anything? In other words, in order for a naturalist to even accept a compatibilist theory of free will, they must solve the problem of mental causation. William Hasker and I have argued that naturalists cannot solve the problem of mental causation, and if I have been right in my discussions here, they cannot consistently even believe in compatibilist free will, much less incompatibilist or libertarian free will.