The principles embodied in the teaching of René Descartes (1596-1650). Its outstanding feature is the notion of universal methodical doubt. Cartesianism begins by calling into doubt whatever knowledge a person has acquired, and then seeking to find a truth so evident that it cannot be doubted. This truth it claims to find in each person's intuition of his own thought and existence. Within the Cartesian system are several principles, all at variance with the Catholic faith, which Descartes professed to believe, namely: occasionalism, which disowns free will for man; ontologism, which denies that a person can perceive ideas within his mind or objects directly in themselves; and angelism, which regards man as if he were a pure spirit within a body, as if thought must be intuitive and not deductive, and independent of things but evolved from one's own consciousness.