John Buridan (ca. 1300-1361) was the most famous philosophy teacher of his time, and probably the most influential. In this important new book, Jack Zupko offers the first systematic exposition of Buridan's thought to appear in any language. Zupko uses Buridan's own conception of the order and practice of philosophy to depict the most salient features of his thought, beginning with his views on the nature of language and logic and then illustrating their application to a series of topics in metaphysics, natural philosophy, and ethics. Part 1 of John Buridan considers the picture of language and logic developed in Buridan's Summulae de dialectica. Buridan systematically overhauled the logic he first learned and later taught at the University of Paris, redeeming the older tradition of Aristotelian logic in terms, propositions, and arguments. This made possible newer and more powerful forms of philosophical discourse. The second part of this volume provides a reading of Buridan's philosophy, showing how this discourse shaped his treatment of speculative questions such as the relation between soul and body, the nature of knowledge, the proper subject of psychology, the function of the virtues, and the freedom of the will. This groundbreaking book is sure to become the standard work on John Buridan.