The Meditations on First Philosophy, which carries the subtitle “In which the existence of God and the immortality of the soul are demonstrated”, is a detailed presentation of the metaphysical and philosophical systems of Descartes that became a fundamental document in the development of western thought and one of the most influential ever written. The book consists of six meditations in a narrative voice that suggests they had taken place in six days; each refers to the previous as “yesterday”.  In the course of the narrative he attempts to discard belief in things which are not for certain and establish what can, in fact, be known for sure. Meditations was one of the first manuscript to undergo peer review: Descartes submitted his manuscript to numerous philosophers and theologians prior to publication, and included the objections and his replies in the first edition. The product of two years of effort, it first appeared in Latin in 1641 and was translated into French as Médiatations Métaphysiques in 1647. The first two meditations, which used the skeptical method of doubt to conclude that only the ego and its thoughts are unquestionably true, exerted a huge impact in the history of philosophy and are considered an indispensable first lesson in modern philosophical thinking.  The Meditations continues to be a standard text in most university philosophy departments.