René Descartes (1596–1650) was a French mathematician, scientific thinker, and philosopher who made important contributions to mathematics, optics, epistemology, and other fields that helped to shape how the modern world came to see nature and the human mind. The son of a lawyer, he was educated at the Jesuit College of La Flèche and in Poitiers, where he studied law. He became a soldier and served in the armies of Maurice, Prince of Orange, and Maximilian I, Duke of Bavaria. He wrote numerous books, in Latin and in French. Presented here is the first edition of his Principia philosophiae (Principles of philosophy), published in Amsterdam in 1644 by the Dutch printer and bookseller Louis Elzevir. The book was an ambitious attempt by Descartes to set forth, in textbook form, an entire system of thought about the nature of matter, the nature of the mind, and the activity of God in creating and setting in motion the universe. The book is in four parts. Part I deals with metaphysics, and such questions as cognition, the sources of human knowledge and understanding, and the relationship between a perfect, all-knowing God and human error, both intellectual and moral. Part II covers the general principles of physics and the theory of the laws of motion. Part III is devoted to astronomical phenomena. Part IV concerns the properties of minerals, metals, magnets, and other natural phenomena and their apprehension by the senses. The book is bound with a second work, Specimina philosophiae, which is a translation from French into Latin, with revisions, of other writings by Descartes, notably his Discours de la méthode (Discourse on the method) of 1637.