Discourse on Method and Meditations on First Philosophy

The Discourse on the Method on the Method of Rightly Conducting the Reason & Searching for Truth in the Sciences (Discours de la méthode pour bien conduire sa raison, et chercher la verité dans les sciences) is a philosophical & mathematical treatise published by René Descartes in 1637. The Discourse is known as the source of "Je pense, donc je suis", which occurs in Part 4. A similar Latin statement, Cogito ergo sum, is found in Principles of Philosophy §7. The La Géométrie appendix introduces the Cartesian coordinate system. The Discourse is influential in the history of modern science. It's a method giving a platform from which all modern natural science could evolve. Descartes tackles the problem of skepticism which had been revived from the ancients such as Sextus Empiricus by authors such as Al-Ghazali & Michel de Montaigne. He modified it to account for a truth he believed incontrovertible, starting his line of reasoning by doubting everything, so as to assess the world from a fresh perspective, clear of preconceived notions.
Meditations on First Philosophy in which the Existence of God & the Immortality of the Soul Are Demonstrated is a philosophical treatise published as Meditationes de prima philosophia, in qua Dei existentia et animæ immortalitas demonstratur in 1641. A French translation, made by the Duke of Luynes under Descartes' supervision, was published in 1647 as Méditations Metaphysiques. It's made up of six meditations, in which he discards all belief in things which aren't absolutely certain, then tries to establish what can be certainly known. The meditations were written as if he meditated 6 days. He actually took several years.
They consist of the detailed presentation of his metaphysical system & in an expansion of his philosophical system, introduced in part 4 of his Discourse on Method. His metaphysical thought is also found in the Principles of Philosophy (1644), intended as a philosophy guidebook.

Text: English, French (translation)