Descartes Knowledge our existence in reality is a question which philosophers have tackled throughout time. This essay will look at the phrase, cogito ergo sum or I think therefore I am, a phrase brought about by Rene Descartes. This phrase is the backbone of Descartes whole philosophy of our existence in reality. As long as we are thinking things, we exist. When we look at this approach to our existence we must first deny that any sensory data that we receive is believable or it is conceivable that it is false. This means that we can’t really know that anything