Descartes: Doubt and Certainty
Stanford Encyclopedia of Philosophy: Descartes’ Epistemology
http://plato.stanford.edu/entries/descartes-epistemology/
Descartes (The School of Life)
Cartesian Skepticism—Neo, Meet Rene: Crash Course Philosophy #5
Cartesian Dualism (Philosophy Tube)
History: Descartes’ Cogito Argument (Wireless Philosophy)