ABSTRACT

In the previous chapter we looked at arguments for and against four-dimensionalism that appeal to criteria of diachronic identity. What is a criterion of diachronic identity? The basic idea is this. The things we encounter belong to different kinds. As we have seen something belonging to one kind can undergo changes that are forbidden to something belonging to a different kind. A piece of clay can survive a deformation in shape that would bring a statue to an end. A chrysalis can turn into a butterfly, but a poached egg cannot. What explains there being constraints on the changes that an object can undergo? Advocates of there being criteria of identity will answer that constraints on the changes that an object can undergo result from the criterion of identity associated with the kind that the object belongs to. Having a shape falling within a fairly narrow range is part of the criterion of identity for statues. But it is not part of the criterion of identity for pieces of clay.