René Descartes, a rationalist philosopher finds uncertainty in almost everything including his senses, memory, body and the physical world. Everything besides the fact he is a res cogitans (thinking thing). He puts forth this idea in his second meditation of his most famous works, Meditations On First Philosophy, published in 1641. This analytic style of writing opens by considering any belief that was the slightest bit doubtful, as false. Descartes felt the need for this “hyperbolic doubt” in order to reach an impartial truth. He then takes you through the thought process that led him to the one thing that lies beyond all doubt. He finds certainty in the statement Cogito, ergo sum or “I think, therefore I am.” In this essay I will explain Descartes’ thinking and reasoning that leads him to this statement, covering his first and second meditation. The first Meditation in Descartes Meditations On First Philosophy, is based on doubting almost everything he once believed as true. When Descartes found that beliefs he had were false, he realized all of his beliefs could be threatened. He embraced skepticism and refused to accept anything that it is possible to doubt. “I realized that it was necessary, once in the course of my life, to demolish everything completely and start again right from the foundations if I wanted to establish anything at all in the sciences that was stable.” Descartes thought the only way to find something that could not be doubted was to remove