Meditations on First Philosophy

Meditations on First Philosophy, in which the existence of God and the immortality of the soul are demonstrated (Latin: Meditationes de Prima Philosophia, in qua Dei existentia et animæ immortalitas demonstratur), often simply called Meditations on First Philosophy or the Meditations, is a philosophical treatise by René Descartes first published in Latin in 1641. The French translation (by the Duke of Luynes with Descartes' supervision) was published in 1647 as Méditations Métaphysiques.

Source: Wikipedia — Meditations on First Philosophy (CC BY-SA 4.0)