Meditations is a discussion of metaphysics, or what is truly real. In these writings, he
             ultimately hopes to achieve absolute certainty about the nature of everything including
             God, the physical world, and himself. It is only with a clear and distinct knowledge of
             such things that he can then begin understand his true reality. Descartes starts by looking
             at our usual sources for truth. Authority, which is churches, parents, and schools, he says,
             are not reliable sources for truth because time shows we all die, and that we are
             eventually proved wrong, much in the same way the accepted truths of science have
             changed dramatically over the course of history. Also, he considers the generally excepted
             view that our senses dependably report the absolute nature of reality. Simiar to authority,
             Descartes discards the senses as a source of truth because of the "Dream Argument" or
             the belief that based on the senses there is no definite way of proving that you are
             dreaming or that you are awake. Therefore it is possible that everything we believe is
             false, making the senses an unreliable source. Upon establishing this, Descartes doubts
             the existence of a physical or external world. Despite that he has an idea of things in the
             world, he has no way of knowing if they exist past his own mind. Another point he
             addresses is mathematics. He soon realizes math's truth isn't completely reliable because
             of the "Demon Hypothesis", which acknowledges the possibility of an all powerful being
             that is deceiving him about everything, including mathematics. As a result, Descartes
             ponders the possibility that he has no way of being completely positive about anything,
             even his existence. It is only after some deliberation that he decides that it is impossible
             to be incorrect about everything because he has doubt, and to posses doubt, there must be
             a doubter. Hence, he doubts, therefore he exis...