The story of Anglophone general jurisprudence and legal philosophy in the twentieth century can be told as a tale of two Boston lectures, separated by sixty years, and their respective legacies. In 1897, Oliver Wendell Holmes, Jr., then Associate Justice of the Supreme Judicial Court of Massachusetts, delivered a lecture to the students of Boston University Law School, which was later published by the Harvard Law Review under the title, “The Path of Law.” Intended largely as advice to young men embarking on the practice of law, the lecture initiated a dynamic new direction for theorizing about law. Although Holmes did not single-handedly turn the ship of American jurisprudence, the thoughts expressed in this essay launched an approach to legal theory that was bold, iconoclastic, pragmatic, and largely innocent of systematic legal philosophy and its history. In the early decades of the twentieth century it inspired progressive-minded legal academics who formed a rag-tag movement which had such a distinctively American cast that it came to be called “American legal realism.” Throughout the first half of the twentieth century, the movement Holmes sired stayed home on American soil. At the same time, the rest of the commonlaw world, led by England, was content to pursue mundane jurisprudential tasks within the comfortable precincts of the province John Austin determined. However, in 1952, H.L.A. Hart’s inaugural lecture, “Definition and Theory in Jurisprudence,” jolted English jurisprudence out of its Austinian complacency and reintroduced it to philosophy. Five years later Hart brought his revived and revised positivist theory to the United States. In 1957, H.L.A. Hart delivered to students of the Harvard Law School his Holmes lecture, later published by the Harvard Law Review under the title, “Positivism and the Separation of Law and Morals.” This essay, and even more its book-length sequel, the classic Concept of Law (1962), launched a revitalized enterprise of philosophically sophisticated jurisprudence that took hold first in Britain and not long after in the United States, Canada, and the rest of the common-law world.