The philosophers usually have thought that if a person knows something, that means that the person believes that (1) the thing is true, (2), is in fact true, and (3) that person who presents claims that he or she know that thing is in a position to give a justification for thinking that thing is true. A justification like that can be offered by appealing to intuition, reasoning, or sense experience. Although intuition is a common concept, in most cases, philosophers have been doubtful to identify it as being a form of knowledge and this is basically for the reason that “there seems to be little way to determine whether it does, in fact, provide knowledge as opposed simply to lucky guesses” (“Epistemology and Descartes”, para 3). Therefore, a large number of philosophers instead put much focus on sense experience and reasoning as being the knowledge bases. The beliefs held by Plato and Descartes are going to be compared and contrasted in relation to the theme of “not knowing” in this paper. Descartes gives out a suggestion that we ask what it would mean to “know about realty” (“Epistemology and Descartes”, para 7). He claims that, to hold a belief that realty is basically “water or Indeterminate or whatever seems pointless, unless we know first whether our belief itself is justified” (“Epistemology and Descartes”, para 7). According to him, in order to determine whether the beliefs we hold are justified, we are supposed to be in a position to trace these beliefs back to an undoubtable statement, certainty, or proposition. A proposition like this could offer a solid foundation on which the beliefs that come thereafter could be erected, it would give assurance that all the claims that come thereafter based on this foundation would be true. In order for us to identify a final standard of truth on which knowledge can be determined, Descartes sets up a technique which suspends our assurance in “what we have been taught, what our senses tell us, what we ‘think’ is obvious, in regard to everything we know” (“Epistemology and Descartes”, para 9). He points out that for us to determine whether there is anything we get to know with assurance; we must first of all doubt everything we know. A radical doubt like this may look unreasonable, and Descartes indeed does not imply we actually have to doubt everything. His suggestion is that, “in order to see if there is some belief that can not be doubted, we should temporarily pretend everything we know is questionable” (“Epistemology and Descartes”, para 9). Because sometimes sense experience is misleading, it is clear to Descartes that a “posteriori” can not form a basis for claim of knowledge (“Epistemology and Descartes”, para 10). “We do not know that what we experience through our senses is true, at least we are not certain”( “Epistemology and Descartes”, para 11). Therefore the best thing to undertake is not to believe our senses. In a similar manner, we can not have certainty that we actually have bodies or that our understanding of our world in general be believed; after all, the whole thing might be just but a dream. In addition, we can’t even be certain that mathematical propositions like 1 + 1= 2 or that rectangles always have four sides are true for the reason that some evil power might be misleading us to think things like these, “when it is possible that even propositions that see