Professor Ernest Weinrib has argued that restitutionary damages must be understood, not as a deterrent to wrongful conduct, but as a requirement of commutative Justice. Professor Gordley agrees, but claims that a purposive understanding of commutative Justice can shed more light on restitutionary damages than the formal understanding of Professor Weinrib. A purposive understanding enables us to distinguish appropriation of a right from mere inteference, to distinguish true restitutionary damages from damages in lieu of a forced sale or hold-up; and to explain why, normally, it should not matter whether the defendant acted wilfully or innocently.