The age of Newton marks one of the great turning points in intellectual history, and Descartes has a key place at its very heart. Designed for students who approach Descartes from the point of view of his philosophy of science, this is the second of a new two-volume edition of the works of Descartes in Penguin Classics. Descartes did major research in optics, geometry, astronomy, and physiology, although (partly because Galileo had just been condemned by the Inquisition) he published nothing until he was over forty. The Discourse forms the preface to his first coLLection of scientific papers, outlining a new method based on hypothesis and deduction, which effectively replaced Adstotelian techniques. This edition puts the work in context by including extracts from Descartes' correspondence, the Rules for Guiding One's Intelligence, and The World -- a posthumously published summary of his physical theories.