Ms. Andrea Solomon, Ms. Mary Edsall
Colloquium F2003x
Assignment #16 – Descartes
30 November 1999
Science From the Ground Up
Like many of his contemporaries, Descartes was interested in a wide range of subjects and he wrote treatises on optics, geometry, meteorology, and so forth, all of which he classified as physics. Like Galileo, Descartes believed that the earth moved, and in his book Le Monde he discussed the planets, comets, stars, the sun, the earth, and how they each either transmit or reflect light. However, when Galileo was tried by the Holy Office in Rome (1633), Descartes feared that a similar fate might await him and he decided to delay publishing. “I had not noticed anything in it [Galileo’s Discourse], before their censuring of it, that I could imagine to be prejudicial either to religion or to the state, nor, as a consequence, had I found anything that would have prevented me from writing it… This made me fear that there might likewise be found among my opinions one in which I had been mistaken… This was sufficient to make me change the resolution I had had to publish my opinions” (34).
Despite his foray into natural sciences (physics), Descartes is much more famous for his extremely methodical work in metaphysics. After all, how can one write about the natural world before one even has reason to believe that it actually exists? Descartes is in many respects the father of epistemology, the philosophical examination of whether the philosopher’s senses can be trusted and thus whether objects (including the philosopher) actually exist. He reasons that before one can examine or discuss anything else, he first has to prove that he, his soul, and God all exist. From this he can establish that his sensory perceptions are at least partially valid (and thus not just a dream), which will be necessary to do before he can comment on the natural world. He calls this fundamental initial step “First Philosophy.”
Descartes compares knowledge to a tree, in which metaphysics is the root, physics is the trunk, and applications of physics (engineering, medicine, etc.) are the branches. In his Discourse on Method, he describes the rigid but incremental steps he took to arrive at his philosophy. First, he threw out everything he knew and established that he could doubt. If nothing else is true, he argues, at least he can doubt, which implies that he exists, thus his famous “cogito ergo sum.” He has established that the thinking or doubting part of him (the soul) exists, but cannot prove that his body is real, therefore there is a clear distinction between body and soul. He then presents two different arguments for the existence of a perfect, non-deceiving god, both of which are arguably less solid (or more circular) than his other proofs. However, having established his and God’s existence, he can achieve his goal of demonstrating that the natural world does actually exist and that we can trust our senses at least to some degree. Because he knows he perceives external objects, that perception can only come from himself, God, or the external objects themselves. Since his perception of the objects does not require thinking (his soul, or true, provable essence), they cannot originate with him. Since God is not a deceiver, God cannot be planting these perceptions into his mind. Thus, the natural world must exist and there is a philosophical justification for science.
Descartes anticipated many criticisms and objections to his arguments and he wrote a series of Replies to Objections. Many philosophers then and since have disagreed with some of the arguments and conclusions he raised, but we are all indebted to the new branch of thinking he created which dominated philosophy for several centuries. His writings in math, science, and metaphysics, as well as his rigorous methods of examination and doubt, rank him as one of the founding figures of modern thought.