DESCARTES, Les Principes de la philosophie, 1681

Fourth edition.
"The Principles of Philosophy" by René Descartes is a fundamental work of Western philosophy. In this treatise, Descartes sets out his vision of the world, based on metaphysical and physical principles. He develops his method of doubt, his famous "cogito, ergo sum" (I think, therefore I am), and his conceptions on the nature of the soul and the body.