The subtitle of Descartes’ Third Meditation is “Concerning God, that He exists,” but the meditation doesn’t really originate in the question of God’s existence. It actually begins with an epistemological question, not a theological one. Descartes admits that he “previously admitted many things as wholly certain and evident” that [he] later discovered to be doubtful.” He must therefore interrogate whether/when the “natural light” that is the marker of evident truth is really true. Only then does he turn to asking about the nature and existence of God, as an originator of this “natural light” that makes truths “clear and distinct” so that his understanding can be trusted. Notice that a feeling of certainty, taken by itself, is defective as evidence for Descartes. These interior markers (natural light, clarity and distinctness) need to be perfected to be fully accepted.
Let’s stop for a moment and think about the difference between a meditation and an argument. Although Descartes will make logical arguments for his position, their logical validity will not make them true unless the premises are also recognized as true. Don’t therefore rely on Descartes’ testimony if you are interested in determining the real meaning of his argument. You, the reader must look within yourself and independently verify that the matter is as Descartes reports. So take a look at what Descartes is asking you to verify: