The first of Descartes meditations discusses his attempt to rid himself of all of his false beliefs. Descartes thinks that in order to do so, he must first rid himself of every one of his former beliefs and start over, only letting back in the beliefs that he can prove true beyond all conceivable doubts. Descartes comes to this conclusion from the assumption that basically, everything you think that you know can be doubted, no matter how basic the concept is or how sure you "feel" about it. Everything can, and should, be doubted.
As Descartes points out, our most foundational beliefs tend to be based on things we perceive through our senses. These include simple, and to us obvious, things such as in Descartes case, that he was sitting in the chair he was sitting in or that his hand he held in front of him, was really even in front of him. Descartes considers that because he has been deceived by his senses on prior occasions, where there was maybe bad lighting or to much distance between him and what he was looking at, that maybe he could be being deceived by his senses at any time.
Further more, he has no proof that he is even awake. For if he was truly sleeping, no, his hand may NOT be infront of him and he may NOT be sitting in the chair; in reality he would really be in bed. According to Descartes, it is very possible to dream and not realize that you are dreaming because it feels real to us while we are dreaming. He feels that this is a prime example of how easily we may be deceived by our senses.
Descartes attempts to find some sort of fundamental fact that is in no way able to be doubted. Because, once he finds that, it is possible to finally start building other truths off of it. However, as Descartes continu ...