Rene Descartes
French mathematician and philosopher. He is known as the founder of analytic geometry, and he contributed to the formation of modern physics; in French speaking world where his influence was strong, there were strong oppositions to the Newtonian idea of gravity (as an action-at-a-distance), since Descartes insisted on action-by-contact.
But he is by far the more important as a philosopher. His method of analysis and synthesis, epistemology on the basis of clear and distinct ideas, mind-body dualism etc., were historically influencial and are still lively issues in contemporary philosophy.