Abstract

Nonreductive physicalism faces a serious objection: physicalism entails the existence of an enormous number of modal facts--specifically, facts about exactly which physical properties necessitate each mental property; and, it seems, if mental properties are irreducible, these modal facts cannot all be satisfactorily explained. The only answer to this objection is to claim that the explanations of these modal facts are themselves contingent. This claim requires rejecting "S5" as the appropriate logic for metaphysical modality. Finally, it is argued that rejecting "S5" is not too high a price to pay for nonreductive physicalism: "S5" should probably be rejected anyway.