Abstract

In this paper I arrive at a view of what it is for all substances to be physical by first arguing for an account of substance dualism as the view that the world is subject to psychophysical laws (or principles in the case of a Principle of Libertarian Choice) of succession PiMj --> PijMij in which some Mj are nonredundant and nonphysical and some Pi are nonredundant and nonmental. This leads to a classification of versions of substance dualism that differs from the traditional classification into epiphenomenalism, interactionism, and parallelism. I reclassify epiphenomenalism as a form of substance physicalism and reject parallelism as incoherent. The position in which there is fundamental mental to mental causation but no fundamental mental to physical causation comes into view as a version of substance dualism that falls outside the traditional classification. Substance physicalism is accordingly analysed as the view that the world is subject to laws of succession whose antecedents are purely physical properties.