This paper argues that there are no necessary and sufficient conditions for the identity through time of material objects where those conditions have a kind of empirical content necessary for them to function as criteria for identity through time. Taking Eli Hirsch’s program in The Concept of Identity as representative of attempts to formulate conditions which are logically necessary and sufficient and which also function as criteria guiding our tracing of objects’ careers through time, I argue (a) that, when such (...) programs are constructed in a way sensitive to the criteria we actually use, they fall prey to conceivable counterexamples and (b) that, when such programs are tightened to avoid logically possible counterexamples, they fail to capture the identity criteria implicit in our ordinary experience. The paper argues that our identity criteria are incomplete and informal and that our individuative practice is partially determined by the kind of interest we have in the object(s) being traced. The relationship between this view and two versions of relative identity is also discussed. (shrink)