Rationalism is the principle that maintains that through reason alone we can gain at least some positive knowledge of the world. The three major rationalists, Rene Descartes, Baruch Spinoza and Gottfried Welhelm Leibniz, used this idea in order to defy skepticism and expose the true nature of reality. However, each philosopher is frequently in disagreement. The idea for ‘God’, and what constitutes substance, matter and reality are the four key structural beliefs that aid each rationalist in the forming of their arguments. Yet, it is these four concepts and the arguments behind them that cause the inconsistency found in rationalism. The idea that reason can provide positive solutions to the various questions put forth is made doubtful through their disparity. Thus, it is through the contradiction of the major rationalist that the viability of rationalism is undermined.
Questions such as; are my senses trust-worthy? What is my essential nature? All pertain to the major question of what constitutes as substance? This issue is the first fundamental conflict between the three philosophers. As Descartes was the first to touch on this problem, I will deal with him primarily. Descartes method of doubt, found in Meditations, was to doubt everything. He did not trust his senses, as they were prone to mistakes. He presented the idea that, as dreams can be so clear and vivid he doubted we could know whether we are dreaming or not. He also stated that we could not know whether our whole concept of reality was real as it could be fabricated by an evil demon. Then, it seems, everything must remain in doubt, not so for Descartes. He found that there is one thing that you can never be deceived on and that is; ‘you cannot doubt that you are doubting.’ You cannot be de ...