  Even so, problems remain. Having extracted clarity and distinctness  as the criterion of truth at the beginning of the Third Meditation, Descartes immediately calls it into question. He re-introduces an element of the radical doubt from the First Meditation: that a powerful God might have created him with “a nature such that I was deceived even in matters which seemed most evident” (7:36). Descartes therefore launches an investigation of “whether there is a God, and, if there is, whether he can be a deceiver” (7:36).