ABSTRACT
This chapter reviews Descartes's theory of knowledge, and discusses that its validity is based on the immediate certainty of intuition. It explains that Descartes refuses to accept this criterion of validity as final, and insists that it must be vindicated by the rational omnipotence of God. The chapter details the nature of the divine guarantee, and observes the diversities of its working among the different kinds of knowledge to secure which it is invoked. An intuition cannot be effectively doubted at the moment of knowledge: just as a percept cannot be effectively doubted at the moment of perception. The knowledge of the self, at any rate at the moment of illumination, is founded on an experience in which the subject, irrespective of the content of its ideas (which, including the eternal verities, are possibly false), affirms its unity with existence in the act of doubting.
