  Despite similarities, Descartes’ version of the argument differs from Anselm’s in important ways. The latter’s version is thought to proceed from the meaning of the word “God,” by definition, God is a being a greater than which cannot be conceived. Descartes’ argument, in contrast, is grounded in two central tenets of his philosophy — the theory of innate ideas and the doctrine of clear and distinct perception. He purports to rely not on an arbitrary definition of God but rather on an innate idea whose content is “given.” Descartes’ version is also extremely simple. God’s existence is inferred directly from the fact that necessary existence is contained in the clear and distinct idea of a supremely perfect being. Indeed, on some occasions he suggests that the so-called ontological “argument” is not a formal proof at all but a self-evident axiom grasped intuitively by a mind free of philosophical prejudice.