Why did René Descartes believe in god?
One of his reasons for believing in god is that he knows (or thinks) that God is perfect. Since perfection includes existence, he therefore assumes that God must exist.
Descartes made a series of increasingly unsupportable suppositions to back up his beleief in God:
1. I exist (A supportable statement for an individual - Cogito ergo sum)
2. I have in my mind the notion of a perfect being (The idea that anyone can develop an idea of a perfect being is not provable. The Aztec may have thoght their bloodthirsty gods perfect as well)
3. An imperfect being, like myself, cannot think up the notion of a perfect being (There is no proof although it is believable that humans are not perfect and it is debatable if the idea he has of a perfect being is indeed perfect)
4. Therefore the notion of a perfect being must have originated from the perfect being himself (This is a flight of fancy)
5. A perfect being would not be perfect if it did not exist (Buddhists, for example see perfection in the loss of being)
6. Therefore a perfect being must exist (This does not follow from any of the above statements)