DESCARTES, Rene, re'na da-kart', dis tinguished French philosopher: b. La Haye in Touraine, 31 March 1596; d. Stockholm, 11 Feb. 1650. He was educated at the Jesuit College of Le Fleche. Here he studied physics and philos ophy according to the scholastic system and showed especial fondness and aptitude for mathematics, which alone seemed to satisfy his demand for certain and clear knowledge. All else that he had learned seemed to him lacking in the clearness and certainty that would entitle it to be ranked as knowledge. After leaving school he went to Paris where he continued his studies. He then enlisted in the military service of the Netherlands and afterward in that of Bavaria. During these years he was always tormented by doubts, and was constantly seeking a method by which he could attain certainty. At length he made the dis covery of his famous principle of certainty which he expressed in the proposition, "I think, therefore, I amp (cogito ergo sum), and which he regarded as "the foundations of a wonderful science.° In 1629 he withdrew into seclusion in Holland, frequently changing his residence that he might continue his work without interruption. Here he lived for 20 years and produced the works upon which his fame rests. In 1649 he accepted the invitation of Queen Christina of Sweden to come to Stockholm and personally instruct her in his philosophy. The Queen pre ferred to have her lectures in philosophy at 5 o'clock in the morning and Descartes had to proceed to the palace at that hour. The severity of the climate and the life at court were in jurious to his naturally weak constitution, and a year after his arrival he contracted an illness from which he died.
Descartes' fame rests not merely upon his contributions to philosophy, however, but also upon his services to physical science and mathematics. He discarded the old methods of
explaining physical phenomena by means of final causes, and insisted that everything takes place mechanically. He is one of the chief pioneers of the mechanical view of the world, and formulates dearly the fundamental laws of this mode of explanation, which he extends to explain all physiological processes. In mathe matics he made important contributions to the theory of equations and was the originator of the science of analytical geometry.
Descartes' principal works are 'The Dis course on Method' which gives a clear account of development of his thought and with which was published his (Dioptrics,)