Lon L. Fuller

Lon Luvois Fuller (June 15, 1902 – April 8, 1978) was an American legal philosopher best known as a proponent of a secular and procedural form of natural law theory. Fuller was a professor of law at Harvard Law School for many years, and is noted in American law for his contributions to both jurisprudence and the law of contracts. His debate in 1958 with the prominent British legal philosopher H. L. A. Hart in the Harvard Law Review (the Hart–Fuller debate) was important in framing the modern conflict between legal positivism and natural law theory. In his widely discussed 1964 book The Morality of Law, Fuller argues that all systems of law contain an "internal morality" that imposes on individuals a presumptive obligation of obedience. Robert S. Summers said in 1984: "Fuller was one of the four most important American legal theorists of the last hundred years".