Global Supervenience and Identity across Times and Worlds

Abstract

The existence and importance of supervenience principles for across times and have been noted, but insufficient attention has been paid to their precise nature. Such attention is repaid with philosophical dividends. The issues in the formulation of the supervenience principles are two. The first involves the relevant variety of supervenience: that variety is global, but there are in fact two versions of global supervenience that must be distinguished. The second involves the subject matter: the names over and across worlds are misnomers, for in neither case is at issue. The philosophical dividends then follow. Nathan Salmon's argument that over time needs no grounds in matters of qualitative fact can be answered, as can an argument offered by many, that coincident objects (such as statues and lumps of clay) would require objectionably ungrounded differences in identities across times and worlds. Supervenience principles assert a kind of functional dependence of one sort of fact on another. They take this form: indiscernibility in such-and-such respect entails indiscernibility in thus-and-so respect. The claim that the mental supervenes on the physical is the claim that the mental is a function of the physical-physical indiscernibility implies mental indiscernibility. Such principles take on interest for various related reasons. One is that asserting supervenience is a maximally cautious way to assert dependence: psychophysical supervenience is something all materialists can agree on, even if they disagree over whether mentality can be reduced in any finite or intelligible way. Another is that supervenience is presupposed by analysis. Various analyses of mentality in physical terms differ in details, but all presuppose supervenience, for a physical analysans will not distinguish between physical indiscernibles, and hence the mental analysandum will not either. Though the philosophy of mind may be the most familiar area in which supervenience has been applied, the same reasons for being interested in supervenience apply elsewhere. The notions of over and transworld identity raise some of the same issues as does mentality. Theses claiming that facts about across and times involve nothing