Descartes, René

(1596-1650)

   philosopher, scholar

   Born in La Haye, Touraine, the son of a minor nobleman, René Descartes began his education at the Jesuit school of La Flèche in Anjou. He studied law at the university of Poitiers, and in 1618 entered the service of the prince of Nassau with the intention of beginning a military career. His attention, however, was soon drawn to philosophy and mathematics. After a period in Italy (1623-24) and in France (1624-28), Descartes settled in the Netherlands, where he spent the rest of his life devoted to the study of philosophy and science. His first major work was Essais, philosophies (1637). In certain essays on geometry, optics, and meteors, and his Discours de la méthode, he presents his philosophical views. This latter work was followed by Méditations métaphysiques (1641) and Principes de philosophie (1644). The latter was dedicated to Princess Elisabeth Stuart of Bohemia, with whom he had a deep friendship. In 1649 Descartes was invited to instruct at the court of Queen Christina of Sweden, and it is there that the rigors of a northern climate caused his death. Descartes's philosophy is based on his attempt to apply the rational inductive methods of mathematics to philosophy. He began his investigation with what was to him the single sure fact expressed in his words "Cogito ergo sum" (I think, therefore I am). His philosophy, sometimes called Cartesianism, led him, however, to a number of erroneous conclusions. He rejected the heliocentric view of the solar system, for instance, and in physiology, misinterpreted the nature of blood in its circulation. In the area of optics, however, his study led him to independent discovery of the law of reflection. Descartes's most important contribution to the study of mathematics was his systematization of analytic geometry. He was the first mathematician to attempt to classify curves according to their types of equation. He also formulated the rule, known as Descartes's rule of signs, for finding the number of positive and negative roots in algebraic equations.