Rene Descartes. Engraving of Rene Descartes (1596- 1650), French mathematician & philosopher, solving a problem. Descartes (at lower centre) was stationed with the French army in the Dutch town of Breda in 1617, where it was the custom to post philosophical questions on the town walls. He asked the head of a local college, Beckman (at lower right), to translate a problem from Flemish into Latin or French. To Beckman's surprise, Descartes immediately solved it. The two became friends, and although Beckman was to claim some of his ideas as his own, they were later reconciled. Descartes coined the phrase I think therefore I am" and made major advances in algebra & geometry."