Meditations on First Philosophy (subtitled In which the existence of God and the immortality of the soul are demonstrated) is a philosophical treatise by René Descartes first published in 1641 (in Latin). The French translation (by the Duke of Luynes with Descartes' supervision) was published in 1647 as Méditations Métaphysiques. The original Latin title is Meditationes de prima philosophia, in qua Dei existentia et animæ immortalitas demonstratur. The title may contain a misreading by the printer, mistaking animae immortalitas for animae immaterialitas, as suspected already by A. Baillet.