Hart H(erbert) L(ionel) A(dolphus) (1907–92), English philosopher principally responsible for the revival of legal and political philosophy after World War II. After wartime work with military intelligence, Hart gave up a flourishing law practice to join the Oxford faculty, where he was a brilliant lecturer, a sympathetic and insightful critic, and a generous mentor to many scholars. Like the earlier ‘legal positivists’ Bentham and John Austin, Hart accepted the ‘separation of law and morals’: moral standards can deliberately be incorporated in law, but there is no automatic or necessary connection between law and sound moral principles. In The Concept of Law (1961) he critiqued the Bentham-Austin notion that laws are orders backed by threats from a political community’s ‘sovereign’ – some person or persons who enjoy habitual obedience and are habitually obedient to no other human – and developed the more complex idea that law is a ‘union of primary and secondary rules.’ Hart agreed that a legal system must contain some ‘obligation-imposing’ ‘primary’ rules, restricting freedom. But he showed that law also includes independent ‘power-conferring’ rules that facilitate choice, and he demonstrated that a legal system requires ‘secondary’ rules that create public offices and authorize official action, such as legislation and adjudication, as well as ‘rules of recognition’ that determine which other rules are valid in the system. Hart held that rules of law are ‘open-textured,’ with a core of determinate meaning and a fringe of indeterminate meaning, and thus capable of answering some but not all legal questions that can arise. He doubted courts’ claims to discover law’s meaning when reasonable competing interpretations are available, and held that courts decide such ‘hard cases’ by first performing the important ‘legislative’ function of filling gaps in the law. Hart’s first book was an influential study (with A. M. Honoré) of Causation in the Law (1959). His inaugural lecture as Professor of Jurisprudence, ‘Definition and Theory in Jurisprudence’ (1953), initiated a career-long study of rights, reflected also in Essays on Bentham: Studies in Jurisprudence and Political Theory (1982) and in Essays in Jurisprudence and Philosophy (1983). He defended liberal public policies. In Law, Liberty and Morality (1963) he refuted Lord Devlin’s contention that a society justifiably enforces the code of its moral majority, whatever it might be. In The Morality of the Criminal Law (1965) and in Punishment and Responsibility (1968), Hart contributed substantially to both analytic and normative theories of crime and punishment. See also LIBERALISM , PHILOSOPHY OF LAW, POLITICAL PHILOSOPHY, RIGHT. D.Ly.