[quote]Well, it proves self existence[/quote]No, it doesn't actually. You see, the 'I' that is apparently proven to exist at the end, is already there at the start. 'I think' already presupposes that I exist, so it cannot therefore be proof that I exist. How do i know i exist? Because I am thinking. But how do I know I am thinking? Because I exist. It's a classic example of circular logic. It's like saying the Bible is true because it is the word of God, and God exists because it says so in the Bible.