Locke on Memory and Personal Identity over Time

John Locke addressed personal identity in Book II, Chapter 27, "Of Identity and Diversity," a chapter added to the second edition (1694) of An Essay Concerning Human Understanding (first published 1689). Locke draws a sharp distinction between "man," identified by the continuity of a single, organized, living biological body over time — the same criterion one would apply to any animal — and "person," which he defines as "a thinking intelligent Being, that has reason and reflection, and can consider it self as it self, the same thinking thing in different times and places." For Locke, sameness of man and sameness of person can diverge: a human body could persist while the person housed in it changed, and, in Locke's own thought experiments, a person could in principle persist across a change of body.