In the second edition of the Essay Concerning Human Understanding, John Locke argues that personal identity over time consists in sameness of consciousness rather than the persistence of any substance, material or immaterial. Something about this view is very compelling, but as it stands it is too vague and problematic to provide a viable account of personal identity. Contemporary "psychological continuity theorists" have tried to amend Locke's view to capture his insights and avoid his difficulties. This paper argues that the standard approach fails because it takes Locke to be a memory theorist, and does not focus enough on his claim that we need continuity of consciousness for personal persistence. An alternative reading of Locke is offered, emphasizing the role of self-understanding in producing continuity of consciousness. This alternative overcomes the difficulties with the standard approach, and shows how it is possible to attribute unconscious psychological elements to a person, even when personal persistence is defined in terms of consciousness.