Rene Descartes argues that since he is capable of being deceived, therefore knows that he is a “thinking thing” (Descartes 65). First, Descartes questions the existence of everything, he begins to doubt if anything is real. After this, he continues by addressing beliefs that rest on his senses, questioning things such as his dreams and how his senses delude him during his sleep. He then continues addressing how the truths of arithmetic and geometry may not be immune to radical doubt. Although the truths of arithmetic and geometry seem so concrete, Descartes continues by supposing that there may exist an “evil genius” who “has employed all his energy to deceive me[him]” (Descartes 65). When he questions how he is certain that he exists, he replies