Rene Descartes was one of the most influential thinkers in the history of the philosophy. Born in 1596, he lived to become a great mathematician, scientist, and philosopher. In fact, he became one of the central intellectual figures of the sixteen hundreds. He is believed by some to be the father of modern philosophy, although he was hampered by living in a time when other prominent scientists, such as Galileo, were persecuted for their discoveries and beliefs. Although this probably had an impact on his desire to publish controversial material, he went on to devise works such as the Meditations on First Philosophy and the Principles of Philosophy Aside from these accomplishments, his most important and lasting mathematical work was the invention of analytic geometry. It seems that the underlying point of Descartes s philosophy is to specify exactly what it is that we are sure we know.
Understanding Descartes philosophy begins with understanding his method of doubt. Think about it like this. Almost everything you believe to be true comes from the senses or through the senses. However, the senses are sometimes deceptive. Since the senses are not completely trustworthy, it is irrational to place complete trust in them. However it is no small leap of faith to presume that everything our senses tells us is false. In fact, it seems almost preposterous to say such a thing. But as Descartes points out, we have dreams regularly and in these dreams everything we experience is a figment of our imagination, or at least not real in the physical sense. So, at least according to Descartes, it is reasonable to doubt everything our senses tell us, for the time being. Now, using similar logic, we can say that everything we have learned from physics, astronomy, medicine, and other such fields are all doubtful. Descartes even believed we could say that such simple, logical statements as 2+3 = 5 or a square has 4 sides could be conceived to be false. Since I judge that others sometimes make mistakes in matters that they believe they know most perfectly, may I not, in like fashion, be deceived every time I add two and three or count the sides of a square We are now at the point where we are doubting everything the world around us, that we have a body, and anything else that we could possibly believe.
Perhaps I even doubt that I exist myself. But in doing this, I am in the act of doubting. How can I doubt something if I do not exist. By the same token, maybe I am deceived into thinking I don t exist by some other entity. But then I must exist for it is I who is being deceived. This is the basic premise of Descartes famous Cogito Ergo Sum I think therefor I am. Here Descartes is not saying anything about what we are here, just that we are. Next his desire is to find out exactly what he is. Well, Descartes states, if I exist, for how long do I exist? I exist for as long as I think, and if I cease to think, then I shall also cease to exist. Therefor, I am nothing but a thinking thing that is, a thing that doubts, understands, affirms, denies, wills, refuses, and that also imagines and senses. Although saying he is all of these things is indeed a bold statement, Descartes feels that in his attempt to prove that he exists he has done all of those things, therefor they must be a part of what he is.
Descartes wants to show that nothing can be perceived more easily and more evidently than my own mind. He starts of with an example of a piece of wax. It seems that this piece of wax, or any corporeal thing for that matter, is more distinctly known by me than exactly what it is that I know. However, we do not really grasp what the wax(or any corporeal object) is through seeing, touching, or imagining, but rather by way of reason perceiving through the mind alone. Since we know what we know about corporeal objects in the same way we know our mind, we must by default know ourselves better than we know these foreign objects. There is not a single consideration that can aid in my perception of the wax or of any other body that fails to make even more manifest the nature of my mind. Now that we seem to know a little bit more about ourselves, and how we perceive things, we can go on to Descartes s proof of God s existence.
Descartes first attempt to prove that God exists is in Meditation Three. Descartes has come to the conclusion that he is a thinking thing based on the simple fact that he clearly and distinctly perceives that he is one. Therefore, using induction, he is able to state as a general rule that everything he clearly and distinctively perceives must be true. Now, Descartes says that he has an idea of God as a perfect, infinite substance. Now, Descartes states that the level of formal reality of the cause of an idea must be at least as great as the level of objective reality in the idea itself. By this logic, I as a finite substance could not possibly cause the idea of an infinite substance. In fact, the only being whose formal reality is large enough to produce the idea of a perfect, infinite substance is a being which is a perfect, infinite substance. Hence, there exists a being which is a perfect, infinite substance, which is my idea of God. So God exists.
The next part of Descartes philosophy deals with his belief that the mind and body are separate. Although the origins of the philosophical separation of mind and body, called dualism, can be traced back as far as the Greek philosophers, and probably before them, Descartes was the first person to write a systematic account of it. Now, Descartes wanted to prove two more things. One, that he actually was an immaterial thing, and two, that there is in fact an external corporeal world
Although Descartes is still a well respected philosopher, it seems that history has judged much of his reasoning as faulty. Kant calls him a problematic idealist for whom there is only one empirical assertion that is indubitably certain, namely that I am Still, even if this is the only true maxim that Descartes discovered, it is indeed a remarkable achievement. Schopenhauer credits Descartes for discovering the only correct starting point in all philosophy. Charles Sanders Peirce, a great American philosopher, said With Descartes, philosophy put away childish things and became a conceited young man.