This paper discusses how Descartes does not accept valid proof for his existence. It explains how, in the process of questioning whether or not he exists, Descartes displays a pattern of reasoning, which proves the validity of the initial question because it arrives at a response that does not just act as proof for his existence ,but as a definition for human beings.
From the Paper:
"Descartes was a doubter, a skeptic whose philosophy emerges from his quest for the truth and his struggle to attain knowledge. As far as he was concerned, there really were no empirical truths but only a set of beliefs which, if they were born out by inquiry and logical testing, became truths. Within this context of doubting all until that all, or its different components, proved to be true knowledge ad reality, Descartes doubted all that was around him. Among the many tings that Descartes doubted was the reality of his own existence. If one were totally honest, one would admit that the first reaction to the idea of someone doubting whether or not he existed, is madness. We know we exist because we can see and feel ourselves."
More papers on Descartes: I Think, Therefore I Am:
Descartes: I Think, Therefore I Am (2012, January 15). Retrieved February 13, 2012, from http://www.academon.com/Essay-Descartes-I-Think-Therefore-I-Am/59365