David Wiggins

British philosopher who developed the sortal theory of identity and persistence — objects persist as the same only relative to a sortal concept — and has argued for a cognitivist view of ethics.

Sameness and Substance: the sortal theory of identity — 'x is the same as y' is incomplete without a sortal concept ('same person,' 'same river'). Identity and Spatio-Temporal Continuity: persistence through time. Needs, Values, Truth: ethical naturalism — moral properties are real features of the world discoverable through reflection on human needs.