Rene Descartes (March 31, 1596 – February 11, 1650) was a French mathematician, scientist and philosopher who made significant contributions to the development of each of these disciplines. He was born in Touraine; his father was a member of Parlement of Brittany and his mother died when he was one year old.  He studied at a Jesuit school and earned a law degree at the University of Poitiers.  At age 24 Descartes had a series of visions in which a divine spirit revealed a new philosophy in which all truths were linked and a fundamental truth applied with rigorous logic would lead to a science of all things. These insights led him to the formulation of analytical geometry and to the notion of applying mathematics to philosophy, which revolutionized both mathematics and philosophy.

In mathematics, he developed analytic geometry, bridging algebra and geometry and elemental to the discovery of calculus, and created the system of Cartesian coordinates. Often called the father of modern western philosophy, he refused to accept the authority of the past and instead resolved to start at the beginning - “as if no one had written on these matters before” - and establish those things we could know for sure and discard those that could not.  In doing so he laid the foundation for rationalism. His most famous statement - “cogito ergo sum” - “I think, therefore I am” - lies at the core of his philosophy, which asserted that the only thing we can know for certain is our own consciousness and thoughts.