“It would be impossible for me to exist, being of such nature as I am (namely, having in me the idea of God), unless God did in fact exist.” Rene Descartes makes many arguments for the existence of God which I think are based in assumptions, as well as giant leaps in logic. Every argument he offers is based in assumptions that not only does God exist, but that we can somehow know his nature. He also makes the assumption that just because we can imagine a perfect being, or one that is superior to ourselves, he must exist. I do not think that is the case. There are plenty of things we can imagine, but have no bearing on reality or our existence. Simply because we can imagine a perfect being does not in any way imply that one exists any more than that if we can imagine unicorns they must somehow exist as well.
Descartes also claims, “I understand by the name ‘God’ a certain substance that is infinite, independent, supremely intelligent and supremely powerful, and that created me along with everything else – if anything else exists. Indeed all these are such that, the more carefully I focus my attention on them, the less possible it seems they could have arisen from myself alone. Thus, from what has been said, I must conclude that God necessarily exists.” Once again, he is making an assumption “the less possible it seems…” which is not a solid argument. Just because something seems less possible to him, does not mean it makes for a good argument. In a similar statement he says “And from the mere fact that such an idea is in me (that of God), or that I who have this idea exists, I draw the obvious conclusion that God also exists, and that my existence depends entirely upon him at each and every moment.” He says “obvious conclusion,” as if that is a valid argument. It does not follow that simply because a conclusion is obvious to someone, it is so to everyone else. Such a claim must be accompanied by sufficient argument to back it up, and I do not think that is the case with Descartes’ assumptions on the existence of God.
There are also many places where his argument is based on an assumption as to the nature of God. He says “…the nature of God is immense, incomprehensible, and infinite…” but he gives no argument or proof that one can indeed know the nature of an invisible being; a being which we cannot perceive, or even infer, with our senses. He also claims that “God is no deceiver,” an argument which would carry weight if, instead of using this claim to back up his other arguments, he had a valid argument to defend why he believed that statement to be true. Basically, I think the only way one could accept Descartes’ arguments on the existence of God would be if one were to already agree beforehand that there is a god and that we can somehow know his nature. I think God exists as a concept, nothing more. The fact that the concept of what an omniscient, omnipotent, all-benevolent, being should be does actually vary from person to person, proves that the nature of that being cannot be known based simply on that concept. If Descartes’ best argument for knowing God’s nature is based on his argument that the concept of God is universal, then it seems to fall flat on its face at this point. So if we cannot know the nature of God, then we cannot know how he thinks or even if he exists.