ABSTRACT
This chapter traces how Rene Descartes's distinctive and immeasurably influential theory of logic and knowledge grew in scope and sophistication as it came under increasing pressure from critics and from Descartes's own demands on it. The rationalist philosophers notably connected logic with metaphysical knowledge. The entire framework for knowledge set up in the Rules, on the hypothesis of maximal doubt, is regarded as no more than a strictly idealist or psychologistic scheme lacking secure connection to reality. Like Descartes, Gottfried Wilhelm von Leibniz believed that logic was, in principle, extremely important for the development of knowledge. The vision, however, included a plan for the kind of highly sophisticated, purely formal manipulation of symbols that characterizes fully modern logic. In Locke's version of intuitive knowledge, the perception of agreement or disagreement of ideas is utterly clear and unmediated by any other ideas.
