 Cartesian foundationalism was the strictest form of classical foundationalism, requiring a deductive metaevidential argument for the reliability of perception. Descartes believed that he could give a non-circular argument for thinking that some perceptual experiences were veridical, by constructing an a priori argument for the reliability of perception. He also aimed for certainty, so his argument was a deductive one, starting with the existence and perfection of God and concluding that any clear and distinct awareness (including elements of perceptual awarenesses) must be true; so some perceptual experiences—namely, the clear and distinct ones—are veridical. This would have licensed a rejection of the Reasons Claim, by showing how we could have a good reason for thinking our experiences to be veridical. However, Descartes’s a priori arguments for the existence of God were at best controversial, and the theology needed to deduce the reliability of perception from the perfection of the deity was unconvincing, so deductive metaevidential arguments along these lines were not pursued further.