One of the things that Descartes was self-consciously doing was elevating the human mind to make it more godlike. He takes very seriously the thesis that human beings are "made in the image of God," and he wants what he interprets as this godlikeness to be a defining mark of his Christian philosophy.
His spin on being made in the image of God takes three forms. First, the mind is transformed from merely the scholastic "form of the body" into a bona fide substance that requires only the concurrence of God to exist. Even though God is the only pure substance, fully satisfying the criterion of independent existence, mind is a really good runner-up, in that it does not require anything other than the concurrence of God to exist. Unlike the scholastic "form of the body" theory, mind does not even need a body. So, the first move is altering mind from merely a form to a substance. Second, the mind is capable of having or acquiring all of its content from sources independent of sense experience. Presumably, because God does not have a body, the contents of the divine mind are totally independent of any sensory data. Whatever it is that God knows, he knows it in a way that does not draw any sources from sense experience. The human mind too is godlike in this way, by means of innate ideas (not just of pure intellectual notions but also of sensory ideas!). Just as God somehow draws his ideas from within himself, so too the human mind, though of course, the faculty by which it does so is implanted by God. This is another way that we are made in the image of God. Third, not only are innate ideas intrinsic and essential to mind qua substance, but also the power of volition. Again, this is a godlike feature that connects with the way that Descartes prosecutes a vigorous divine voluntarism about so-called true and immutable natures (e.g., necessary truths of logic, mathematics, and ontological kinds). These truths are dependent on the divine will. Minus his own divine will, even God could not come to believe these truths. In an analogical fashion, the human mind, according to Descartes, would not be able to believe anything without the exercise of its own will. So, a Cartesian doxastic voluntarism is built into Descartes' theory of mind for metaphysical reasons and not because Descartes was sensitive to epistemic deontology.
