I'm a philosophy minor, and lately, as it usually happens in these philosophy classes involving early modern philosophy, we've been discussing "The Meditations". Descartes' claim to fame, philosophically anyways, was the meditations, which helped him to become known as the "Father of modern philosophy." In the meditations, he discusses how one cannot trust the senses, and that you can be more sure of the existence of the soul and of God than of the existence of your own hand. However, I have found his argument to be quite shaky, especially when compared to Anselm's argument. To simplify Anselm's argument, which is more or less Descartes' argument:
1) God is perfect in every way including existence
2) Therefore God exists.
The argument seems stupid and flawed to the untrained observer, so I shall provide some background on the argument. The theological and the philosophical God are a bit different. The theological God is based mostly on the Bible, while the philosophical God is more the idea of a perfect being, or "That of which none greater can be conceived." So God is more an idea than anything else in philosophy. So assuming that God is an idea that is self-causing (which is freaking ridiculous, but we'll avoid that topic for another thread) and is considered to be the triple O God, or Omniscient, Omnipotent, Omnibenevolent.
The Argument of Evil is one of the main sources of opposition to the existence of the triple O God. It draws upon the point that if God is perfect, why does he allow evil in the world? If God is perfect, why did he let someone be raped, or let those people be killed, or even just let me fail that exam? I'm curious as to your opinions on these topics Facepunch.
Links for those who want to look at these arguments a bit more: