Abstract
'Object' and 'criterion of identity' are philosophical terms of art whose application lies at a considerable theoretical remove from the surface phenomena of everyday linguistic usage. This partly explains their highly controversial status, for their point of application lies precisely where the concerns of linguists and philosophers of language merge with those of metaphysicians. This chapter explains the possession of determinate identity‐conditions. It argues that the distinction between 'abstract' and 'concrete' objects is itself a highly controversial one, and although it has indeed been argued that this distinction turns ultimately upon differences between the criteria of identity governing objects of these two broad categories. It examines the role which criteria of identity play in our talk about objects of the least controversial varieties. The chapter concerns the problem of identity over time and the paradoxes to which identity criteria often appear to give rise when time is brought into the picture.