Principles of Philosophy is a book by René Descartes. In essence it is a synthesis of the Discourse on Method and Meditations on First Philosophy It was written in Latin, published in 1644 and dedicated to Elisabeth of Bohemia, with whom Descartes had a long-standing friendship. A French version followed in 1647. It set forth the principles of nature—the Laws of Physics—as Descartes viewed them. Most notably, it set forth the principle that in the absence of external forces, an object's motion will be uniform and in a straight line. Newton borrowed this principle from Descartes and included it in his own Principia; to this day, it is still generally referred to as Newton's First Law of Motion. The book was primarily intended to replace the Aristotelian curriculum then used in French and British universities. The work provides a systematic statement of his metaphysics and natural philosophy, and represents the first truly comprehensive, mechanistic account of the universe.
Original Latin: Veritatem inquirenti, semel in vita de omnibus, quantum fieri potest, esse dubitandum
Variant translation: If you would be a real seeker after truth, you must at least once in your life doubt, as far as possible, all things.
Principles of Philosophy (1644)
Variant: In order to seek truth, it is necessary once in the course of our life, to doubt, as far as possible, of all things.
