Everyday we are bombarded with various forms of stimuli. We see many people, we hear cars drive by, we feel the cool breeze, etc, but how can we prove that we are really experiencing these stimuli? That is the question that Rene Descartes asked some three hundred fifty years ago, is there anything real in this world? Descartes concluded that at least his mind existed because he was thinking, which led to him saying, "Cogito ergo sum" which means "I think therefore I am". In this essay I will briefly discuss Descartes' theory, and discuss alternative opinions of such a theory, and all the consequences it carries along with it.
             Descartes convinced himself that nothing really existed, our bodies our friends all we know and love. He believes that all of the outside stimuli are some how not naturally put in ones mind to create a false sense of reality. Would this make Descartes nonexistent as well as his body and mind? Not necessarily, it wouldn't because he doubts existence and how can there be doubt if there isn't anybody to do the doubting. In other words in order to believe in the falseness of the entire universe, one still has to exist in order to believe. And believe can only exist in the mind, according to Descartes. Now that he had proved the existence of the mind, he could move on to doubt everything else, such as what we saw, heard, tasted, felt, and smelled.
             Descartes supposed that there was a demon, an evil one that was spending all of its time deceiving him and everyone else in the world. The demon would plant illusions in his and everybody's head to make us believe that we are seeing, touching, tasting, hearing, and smelling, things that are not really there or completely different for what our human mind perceives. It may even be deceiving us into thinking that we have a physical body. Descartes believed that the demon could deceive h
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