The Enduring Legacy of John Austin’s Legal Positivism in American Jurisprudence. In the realm of legal philosophy, John Austin stands as a towering figure, particularly for his seminal contributions to the theory of legal positivism. His work, particularly his magnum opus. The Province of Jurisprudence Determined, has profoundly influenced the evolution of American legal thought. It has a great role on shaping its foundations and guiding its development.