Georges Canguilhem is one of France's foremost historians of science. Trained as a medical doctor as well as a philosopher, he combined these practices to demonstrate to philosophers that there could be no epistemology without concrete study of the actual development of the sciences and to historians that there could be no worthwhile history of science without a philosophical understanding of the conceptual basis of all knowledge. A Vital Rationalist brings together for the first time a selection of Canguilhem's most important writings, including excerpts from previously unpublished manuscripts and a critical bibliography by Camille Limoges. Organized around the major themes and problems that have preoccupied Canguilhem throughout his intellectual career, the collection allows readers, whether familiar or unfamiliar with Canguilhem's work, access to a vast array of conceptual and concrete meditations on epistemology, methodology, science, and history. Canguilhem is a demanding writer, but Delaporte succeeds in marking out the main lines of his thought with unrivaled clarity; readers will come away with a heightened understanding of the complex and crucial place he holds in French intellectual history.