The Physicalist's Tight Squeeze: A Posteriori Physicalism vs. A Priori Physicalism

Abstract Both a priori physicalism and a posteriori physicalism combine a metaphysical and an epistemological thesis. They agree about the metaphysical thesis: our world is wholly physical. Most agree that this requires everything that there is must be necessitated by the sort of truths described by physics. If we call the conjunction of the basic truths of physics P, all physicalists agree that P entails for any truth Q. Where they disagree is whether or not this entailment can be known a priori . The a priori physicalist says it can, the a posteriori physicalist says it cannot. Though a posteriori physicalism is probably the dominant view, it is really a surprising and somewhat unlikely stance. In this article, the nature of the view is discussed, and two arguments are presented that should cause us to look again at the potential of a priori physicalism.