Derek Parfit

British moral philosopher whose Reasons and Persons is one of the most original works of 20th-century moral philosophy — arguing that personal identity is not what matters, and developing population ethics.

Reasons and Persons: three major arguments — (1) self-defeating theories of rationality (egoism, consequentialism, contractualism); (2) personal identity: we are not separately existing entities distinct from our psychology — identity is not what matters (continuity of psychology is); (3) population ethics: the Repugnant Conclusion and the non-identity problem. On What Matters: a mammoth attempt to unify consequentialism, Kantianism, and contractualism.