Portrait of the French mathematician, philosopher & physiologist Rene Descartes, 1596-1650. Living on his modest inherited wealth Descartes travelled, studied & wrote, & served as a soldier in Holland, Bohemia and Hungary. He died soon after becoming tutor to Queen Christina of Sweden. He created analytical geometry, which translates geometrical problems into algebraic form so that algebraic methods can be applied to their solution. Conversely he applied geometry to algebra. He propounded Cartesian dualism, stating that mind & matter are two distinct substances which can interact; he believed God to be the prime mover of matter, and that everything has a cause.