Lon L. Fuller

Life and ideas

Lon Fuller taught at Harvard, where he became a leading scholar of contract and of the philosophy of law. In 1958 he answered H.L.A. Hart's defence of the separation of law and morals in the Harvard Law Review, using the problem of the Nazi-era informer to show why a legal system cannot be morally neutral. His book The Morality of Law (1964) sets out eight principles of an 'inner morality' of law: laws must be general, public, not retroactive, clear, not contradictory, possible to obey, reasonably constant and actually applied as announced. A system that fails them all, he said, is not merely bad law but no law at all. He thought of this as a procedural natural law, an inner morality that makes law a purposive activity. He also wrote the classic teaching case of the speluncean explorers.