In this thesis I argue for a novel interpretation of Book II, Chapter xxvii of Locke's Essay concerning Human Understanding according to which Locke's theory of identity is taken to be an Aristotelian four-causal theory. On this interpretation, we are the same person as anyone who efficiently causes us to remember being them. More particularly, two diachronically distinct persons x and y are the same person just in case either x causes y to remember being x or y causes x to remember being y; and two contemporaneous persons x and y are the same just in case for all diachronically prior persons z, z causes x to remember being z if and only if z causes y to remember being z. While this interpretation suffers from the drawbacks that Locke nowhere articulated such a view and had a well-known antipathy for scholastic notions generally, I argue that it has certain advantages. In addition to being at least consistent with Locke's dicta on causation, it is both formally and substantively adequate. Moreover, it reflects Locke's unconscious enmeshment in scholastic notions, and is useful as a heuristic; it sheds light on some of the more obscure aspects of the text (e.g., §12 and the concept of "man"). I conclude with the hope that future research will provide even more support for this novel interpretation.