"H. L. A. Hart (Herbert Lionel Adolphus Hart) (1907–1992) is considered one of the most important legal philosophers of the twentieth century. He is the author of The Concept of Law and was Professor of Jurisprudence at Oxford University. Hart developed a sophisticated theory of legal positivism within the framework of analytic philosophy.

Hart was...the son of a Jewish tailor of German and Polish origin. [He was] [e]ducated at...New College, Oxford, where he studied Classical Greats. Hart became a Barrister and practiced at the Chancery Bar from 1932 to 1940. During World War II, Hart worked with MI5, a division of British military intelligence. In 1945, he was appointed a tutor at New College, Oxford. In 1952, he was selected the Professor of Jurisprudence at the University of Oxford. He resigned the Chair in 1969, and was succeeded by Ronald Dworkin.

More than any other person, Hart revolutionized the methods of jurisprudence and the philosophy of law in the English speaking world. Influenced by J. L. Austin and Ludwig Wittgenstein, Hart brought the tools of analytic, and especially linguistic, philosophy to bear on the central problems of legal theory. Hart's method combined the careful analysis of twentieth century analytic philosophy with the jurisprudential tradition of Jeremy Bentham, the great English legal, political, and moral philosopher. Hart is widely considered responsible for bringing English-language jurisprudence into the philosophical main-stream." (from Wikipedia.com)

His publications include Causation in the Law, with Tony Honore (1959); The Concept of Law (1961), Law, Liberty and Morality (1963), and The Morality of the Criminal Law (1965).