Locke's place-time-kind principle

Locke's place–time–kind principle, also called Locke's thesis, is a claim in the philosophy of John Locke that no two things of the same kind can occupy the same place at the same time, and that no single thing can be in two places at once. In contemporary discussions of Locke, the principle is often used to summarize and interpret the opening of his chapter "Of Identity and Diversity" in An Essay Concerning Human Understanding (1690).

In Locke's own presentation, the principle functions as part of his account of identity and individuation: when we ask whether something is "the same," we refer it to a determinate time and place of existence, where it excludes other things of the same kind. Locke also ties this thought to the idea of solidity (impenetrability), defining solidity as a body's resistance to the entrance of another body into the place it possesses.

There are some counterexamples to Locke's thesis in the philosophical literature.