Descartes and Assumptions

Something that I really admired about Descartes' Meditations was how he started by eliminating any certainty of existence, and then worked forward to determine what does actually exist. However, I am still unconvinced that Descartes has proven the existence of God. I do think that he has proven that he believes in the existence of God, but I am still wondering whether it is possible to imagine an infinite concept while still being a finite individual. Personally, I find his argument flawed in that he takes for granted this idea that having a concept of the infinite implies that the infinite exists. In Meditation Four, he attempts to strengthen his argument by saying, “I acknowledge that it is impossible for God ever to deceive me, for trickery or deception are always indicative of some imperfection. And although the ability to deceive seems to be an indication of cleverness or power, the will to deceive undoubtedly attests to maliciousness or weakness. Accordingly, deception is incompatible with God” (122-123). Clearly, Descartes is working under the assumption that God does not posses the will to deceive because he is neither malicious nor weak. While I can agree that God is not weak, the maliciousness of God is up for consideration. Simply put, when writers are working with an unstated and unsupported assumption, I would like for the assumption to be indisputable enough to dispel any need for additional support.