Gottfried Wilhelm Leibniz (July 1, 1646 – November 14, 1716) was a German philosopher and mathematician. In regards to the former role, Leibiniz was one of the three greatest advocates of rationalism in the 17th Century, along with Rene Descartes and Baruch Spinozoa. His philosophy is mostly noted for its theistic optimism: i.e., for his conclusion that the universe we find ourselves in was the best of all worlds that God could have created. In regards to the latter role, Leibniz developed the calculus of infinitesmals contemporaneous yet indepedently of Isaac Newton, and his clear mathematical notion is generally used in calculus textbooks even to this today (in lieu of Newton's rather more complicated, deliberately obscure form of notation).