Meditationes de Prima Philosophia: in Latin, with introduction in German

According to Wikipedia: "René Descartes (31 March 1596 11 February 1650), also known as Renatus Cartesius (latinized form),[2] was a French philosopher, mathematician, scientist, and writer who spent most of his adult life in the Dutch Republic. He has been dubbed the "Father of Modern Philosophy," and much of subsequent Western philosophy is a response to his writings, which continue to be studied closely to this day. In particular, his Meditations on First Philosophy continues to be a standard text at most university philosophy departments. Descartes' influence in mathematics is also apparent, the Cartesian coordinate system allowing geometric shapes to be expressed in algebraic equations being named for him. He is accredited as the father of analytical geometry. Descartes was also one of the key figures in the Scientific Revolution."