Abstract

In the dissertation I first define and describe both reductive and nonreductive physicalism. In defining reductive physicalism I solve the problem posed in the question "is it reducibility to present or future physics which determines what is physical?" The former does not seem right; future physics itself will not reduce to present physics and so, absurdly, will not count as physical. The latter seems hopeless because it lands us with the difficulty of saying what it is for a future physics to be physical. I use my resolution of this dilemma to motivate an account of reduction as theory explanation involving identifying psychological properties with physical or functional properties. I then define nonreductive physicalism, resolving an analogous dilemma. Nonreductive physicalism is compatible with psychology's being true but irreducible. Reductive physicalism is not; it requires that psychology reduce or be eliminated. Determining what the application of physicalism requires of psychology thus demands determining which variety of physicalism should be adopted. This is the principle focus of the dissertation. I examine the mesh argument for reductive physicalism, according to which either the reduction or elimination of psychology is required to explain how behaviour is predictable and explicable in both neuroscientific and psychological terms. I claim that there are a number of nonreductive responses to the mesh argument, defending as the most promising one based on the laws of psychology and neuroscience's both being true: that is why both can furnish true predictions and explanations of the same behaviour. In defending this response I also reply to the traditional reductive physicalist objection that nonreductive physicalism cannot properly account for psycho-physical causation. However, I ultimately argue against nonreductive physicalism. I argue that the tokens of a given psychological property must objectively resemble each other; they must all have something in common. But the nonreductive physicalist cannot allow that they do without compromising her commitments to nonreduction or physicalism. I am thus led to the view that physicalism as applied to psychology requires either its reduction or elimination