Ren? Descartes was an influential French philosopher, scientist and mathematician who revolutionized the fields of geometry, algebra and philosophy. He is best known for his famous phrase "cogito ergo sum" ("I think, therefore I am") which formed a cornerstone of modern philosophical thought. His work on analytic geometry would go on to shape the field of mathematics and played an integral part in the Scientific Revolution. A stalwart adherent to rationalism, Descartes asserted absolute freedom in God's act of creation allowing him to reject prior authority from other philosophers. The Meditations on First Philosophy he wrote serves as a standard text amongst university courses around the world today. With contributions such as these to science and knowledge at large, it is no surprise why Ren? Descartes has become regarded by many as one of history's key figures in Western thought with much still learned from this great thinker even centuries after his death.