Descartes was known as philosopher and mathematician, famous for his Cartesian system. This book “Meditations” consists of six parts, in the first of which the author expounds his philosophy of doubt; in the second, he reaches the certainty of his own being, through the use of his famous maxim, cogito, ergo sum (I think, therefore I am); in the third, he deduces an argument to prove the existence of God from the idea of an infinite and sovereignly perfect being; in the fourth, he draws a distinction between speculative reasoning, for which the light of nature is sufficient, and doctrines of faith and the conduct of life, which rest on another foundation; in the fifth, he explains the corporeal nature, and brings forward another argument for the existence of God; and in the sixth he treats of the distinctions between intellect and imagination, the difference yet intimate connection of soul and body, errors of the senses and the means of avoiding them, and the reasons upon which we can conclude concerning the existence of material things, which he, however, regarded as inferior to the evidence on which we predicate the existence of God and the soul.