 Students of philosophy can expect to be taught a longstanding interpretation according to which Descartes’ broader argument is viciously circular. He first argues from clearly and distinctly perceived premises to the conclusion that an all-perfect God exists; he then argues from the premise that an all-perfect God exists to the conclusion that whatever is clearly and distinctly perceived is true. The worry is that he presupposes the C&amp;D Rule in the effort to prove the C&amp;D Rule. Despite its prima facie plausibility, Descartes scholarship generally resists the vicious circularity interpretation, based on numerous textual considerations. But even putting those texts to the side, it should be surprising that the project would be viciously circular. As Thomas Lennon notes: