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 clea