The Rationalism of Descartes and Leibniz Although philosophy rarely alters its direction and mood with sudden swings, there are times when its new concerns and emphases clearly separate it from its immediate past. Such was the case with seventeenth-century Continental rationalism, whose founder was Rene Descartes and whose new program initiated what is called modern philosophy. In a sense, much of what the Continental rationalists set out to do had already been attempted by the medieval philosophers and by Bacon and Hobbes. But Descartes and Leibniz fashioned a new ideal for philosophy. Influenced by the progress and success of science and mathematics, their new program was an attempt to provide philosophy with the exactness of mathematics. They set out to formulate clear and rational principles that could be organized into a system of truths from which accurate information about the world could be deduced. Their emphasis was upon the rational ability of the human mind, which they now considered the source of truth both about man and about the world. Even though they did not reject the claims of religion, they did consider philosophical reasoning something different than supernatural revelation. They saw little value in feeling and enthusiasm as means for discovering truth, but they did believe that the mind of an individual is structured in such a way that simply by operating according to the appropriate method it can discover the nature of the universe. The rationalists assumed that what they could think clearly with their minds did in fact exist in the world outside their minds. Descartes and Leibniz even argued that certain ideas are innate in the human mind, that, given the proper occasion, experience would cause these innate truths to become self-evident. That the highly optimistic program of rationalism was not altogether successful is indicated in the differences of the systems it produced. These two rationalists fi...
