Explain Descartes proof for the existence of God. What fallacy does this argument commit? Do you find this argument convincing or not? How might he have argued more convincingly, if at all?...

Explain Descartes proof for the existence of God. What fallacy does this argument commit? Do you find this argument convincing or not? How might he have argued more convincingly, if at all?
http://www.classicallibrary.org/descartes/meditations/