Descartes's Secret NotebookBy: Amir D. Aczel Ren Descartes (15961650) is one of the towering and central figures in Western philosophy and mathematics. His apothegm Cogito, ergo sum marked the birth of the mind body problem, while his creation of so called Cartesian coordinates have made our physical and intellectual conquest of physical space possible. But Descartes had a mysterious and mystical side, as well. Almost certainly a member of the occult brotherhood of the