Born March 31 in La Haye, in Touraine, France, the third child of a councillor of the parliament of Brittany, Descartes has often been described as the father of modern philosophy. He was educated at the Jesuit college of La Flèche, where he studied until 1612, with his last years at the college given to the study of logic, philosophy, and mathematics. While Descartes later wrote affectionately of his Jesuit teachers, he was dissatisfied with his instruction because he felt it mainly transmitted received opinions of the ancient philosophers and lacked a solid foundation. Mathematics, which played such a pivotal role in Descartes' philosophical development, was the one exception. In it he found the certainty and clarity he sought. In 1618, seeking knowledge that would be useful for life, Descartes enlisted in the army of Prince Maurice of Nassau, though he left the following year for Germany and joined...