  Because of its simplicity, Descartes’ version of the ontological argument is commonly thought to be cruder and more obviously fallacious than the one put forward by Anselm in the eleventh century. But when the complete apparatus of the Cartesian system is brought forth, the argument proves itself to be quite resilient, at least on its own terms. Indeed, Descartes’ version is superior to his predecessor’s insofar as it is grounded in a theory of innate ideas and the doctrine of clear and distinct perception. These two doctrines inoculate Descartes from the charge made against Anselm, for example, that the ontological argument attempts to define God into existence by arbitrarily building existence into the concept of a supremely perfect being. In the Third Meditation, the meditator discovers that her idea of God is not a fiction that she has conveniently invented but something native to the mind. As we shall see below, these two doctrines provide the resources for answering other objections as well.