 An argument for perdurance which has been hotly debated is due to David Lewis (1986). If perdurance is rejected, the ascription of dated or tensed properties to objects must be regarded as assertions of irreducible relations between objects and times. If Tabby is fat on Monday, that is a relation between Tabby and Monday, and if perdurance is rejected it is an irreducible relation between Tabby and Monday. According to perdurance theory, however, while it is still, of course, a relation between Tabby and Monday it is not irreducible; it holds between Tabby and Monday because the temporal part of Tabby on Monday, Tabby-on-Monday, is intrinsically fat. If perdurance is rejected, however, no such intrinsic possessor of the property of fatness can be recognised: Tabby’s fatness on Monday must be regarded as an irreducible state of affairs.