The father of modern philosophy, born at La Haye, in Touraine; was educated at the Jesuit College of La Flèche, where he made rapid progress in all that his masters could teach him, but soon grew sceptical as to their methods of inquiry; "resolved, on the completion of his studies, to bid adieu to all school and book learning, and henceforth to gain knowledge only from himself, and from the great book of the world, from nature and the observation of man"; in 1616 he entered the army of the Prince of Orange, and after a service of five years quitted it to visit various centres of interest on the Continent; made a considerable stay in Paris; finally abandoned his native land in 1629, and betook himself to seclusion in Holland in order to live there, unknown and undisturbed, wholly for philosophy and the prosecution of his scientific projects; here, though not without vexatious opposition from the theologians, he lived twenty years, till in 1649, at the invitation of Christina of Sweden, he left for Stockholm, where, the severe climate proving too much for him, he was carried off by pneumonia next year; Descartes' philosophy starts with Doubt, and by one single step it arrives at Certainty; "if I doubt, it is plain I exist," and from this certainty, that is, the existence of the thinking subject, he deduces his whole system; it all comes from the formula Cogito, ergo sum, "I think, therefore I exist," that is, the thinking ego exists; in which thinking philosophy ere long sums the universe up, regarding it as a void, without thought; Descartes' philosophy is all comprehended in two works, his "Discourse on Method," and his "Meditations" (1596-1650).