Epicurus promoted atomism and an asceticism based on freedom from pain as its ultimate goal. Gassendi's concept was closer to classical atomism, but with no atheistic overtone. Aristotle and his student Theophrastus explicitly credit Leucippus with the invention of atomism. Augustin-Louis Cauchy (1823) defined the differential without appeal to the atomism of Leibniz's infinitesimals. The natural philosophy of atomism appeared in several ancient traditions. Buddhist atomism and the Jaina school continued the atomic tradition. Russell became an advocate of logical atomism. Wittgenstein developed a comprehensive system of logical atomism in his "Tractatus Logico-Philosophicus" (, 1921). It is a form of atomism in natural philosophy. His best known intellectual project attempted to reconcile Epicurean atomism with Christianity. The early theory of atomism can be traced back to ancient Greece and ancient India. The main difference between atomism and Descartes' concept was the existence of the void. Via Russell's logical atomism, ordinary language would break into discrete units of meaning. He was also one of the primary theorists of Buddhist atomism. The Royal Society, chartered in 1662, advanced Epicurean atomism.