Rene Descartes was a French philosopher, mathematician, and scientist who lived between 1596 and 1650. His writings mark the dividing line between the empiricist school of thought and the rationalist school of thought. A great deal of this thought was based on information gleaned from the senses. Descartes felt the only way to obtain true knowledge was to rely solely upon human reason while ignoring the senses.
In Discourse on Method, Meditation III builds off of Descartes’ earlier idea that he exists because he is capable of thinking – “I think, therefore I am.” Assuming that what he is able to perceive as distinct must be true, he strives to erase his mind of all information that has been gained through his five senses to arrive at what he knows deep within himself. One of the first things that he perceived in this line of thought was that he had a basic idea of the existence of God. Since that idea had to have had a cause of some kind, because he had already proven that nothing comes from nothing, Descartes reasoned that this cause must have at least as much reality as the idea itself. At the same time, since he did not consider himself infinitely perfect, Descartes reasoned he could not have been the cause of this idea, so there must be an outside cause that is infinitely perfect – in other words, God must exist.
Descartes’ second argument to prove God’s existence lies in his ability to conceive of something perfect despite his own fallibilities. This second argument begins with the knowledge that he exists – again, “I think, therefore I am.” This existence must have a cause of some kind, which Descartes determines to be one of five possibilities. The first is that his existence stems from himself, but if he had created himself, he would have made himself perfect. Since he is not perfect, he could not have made himself. The second possibility is that he is merely a continuation of something that has always existed. However, scientific studies have shown, even in Descartes’ time, continued existence does not necessarily follow from present existence, such as in the case of death. The physical explanation is that his parents were the cause of his existence, but this line of reasoning was determined to lead to an infinite regress and therefore unproductive to follow. If he were made by something that was less perfect than God, as in the fourth possibility, Descartes would still be left searching for the concept of something supreme, which something less perfect than God would not provide. Having eliminated all but one of the five possibilities, Descartes is able to declare with confidence that God exists as he is the only being that meets all of the necessary requirements that have been established.
Although there are some significant holes in Descartes’ logic that have been pointed out throughout the centuries since he wrote it down, Descartes’ procedure of doubtful questioning, constantly bringing his assumptions under suspicion, helped to change the course of modern philosophy, raising significant questions regarding the nature not only of the universe but of knowledge and the separation between the body and the mind. His meditation proving the existence of God is perfect for illustrating how this line of questioning functioned to change the way in which scientists of his day were changing the way they approached their investigations.
References
Descartes, R. 2001. Discourse on Method. Vol. XXXIV, Part 1. The Harvard Classics. New York: P.F. Collier & Son, 1909–14; Bartleby.com. Web.
Descartes, R. 1989. Meditations on First Philosophy. Trans. John Veitch. New York: Prometheus Books.