Abstract

Substratism and Replacementism are the two major contending accounts of intrinsic change. This chapter discusses the interaction between composition and persistence, as the persistence of composite objects provides a critical test case for evaluating these two accounts. The chapter covers important puzzles and paradoxes for those who believe that mereological inconstancy and mereological coincidence are possible. There are actually two somewhat different conceptions of coincidence. One involves the sharing of a time‐slice or instantaneous temporal part. This is Temporal Coincidence. A second kind of coincidence involves having exactly the same parts (whether spatially or temporally extended or both) at the same time. On some views, Temporal Coincidence and Temporary Mereological Coincidence are exactly the same things. The most compelling case of temporary mereological coincidence is that of composite things and their matter.