A person changes in body, memory, and character over a lifetime, yet is ordinarily counted as one and the same person throughout. Psychological continuity, Locke's answer as later philosophers refined it, places that sameness in overlapping chains of memory and psychological connection linking earlier and later stages of a life. Hume's bundle theory denies that anything persists to be re-identified: a self is a bundle of changing perceptions, and its identity over time is a fiction the mind builds from the resemblance and causal links among them.
This is distinct from whether an enduring self exists at all — a prior question the map treats separately under Existence of the Self.