Part of Descartes' attempt to prove the existence of God, without assuming the existence of God. He starts, je pense, donc je suis. (he was French.)
  1. I am thinking this. I can think.
  2. Well, then, I must exist.
  3. If I exist, I must have come from somewhere.
  4. I must have a creator, e.g. God.
Of course, this is not a proof. He wasn't satisfied with it and apparently wasn't very happy that he couldn't absolutely prove God's existence. He did better in math. I am not a philosopher, this is just what i remember.

General Wesc has given me a more authentic-sounding series of steps, one which would convince me less, even. So - "I think, therefore God is, in three easy steps", by our friend Rene:

  1. People have an idea of a perfect being.
  2. Every effect must have an equal or greater cause.
  3. The only cause that could be equal/greater than that idea is God.
Ah, Rene. So the butterfly influencing the weather patterns is no good for you, eh? And the idea of a perfect being held in the mind of a human is the next greatest thing to a perfect being itself? Personally, i think a good ripe peach is equal to or greater than musings on a perfect being most days. But then, i am not desperate to prove i have a creator other than my mother.

Thanks, Wesc!