Failures of René
Descartes objective in the Meditations was to structure human knowledge on a solid foundation. In reviewing his own beliefs, he realized that many were conflicting, others inconsistent, and some more justified than others. He wanted to assign order to his jumble of beliefs so that as in the certainty of mathematics, the justification of one proposition could follow from another. In his studies of certainty he found that many things he was trying to solve, prove, or supported were opposing on another and so he was only contradicting himself. Though he did not actually have "failures" so to speak he had many things that did not seem to work out logically that were later pointed out by Pierce. Either René had very small undocumented failures or he simply had self contradictions but either way there weren't many to specify here. He was a brilliant philosopher that set a firmly bound base for the questioning of sources of knowledge. He was also able to say that the only thing that we are truly certain of is our existence, or "cogito ergo sum."