Rene Descartes (1596-1650), French mathematician and philosopher. The circular Latin inscription names him Renatus Des-Cartes, with his self-styled title of Lord of Perron, and refers to his birth in La Haye (now called Descartes) in Touraine (an area of France) on the last day of March in 1596. Descartes created a co-ordinate geometry, known as Cartesian geometry, and is also considered to be the father of modern philosophy: he stated, I think, therefore I am". Artwork from a 1644 book by Dutch mathematician Franciscus van Schooten, who popularized Descartes' work. The Latin text at bottom is credited to the Dutch poet Constantijn Huygens (1596-1687), who knew Descartes."