Does God exist?

Reading through the discussion thread this week I saw many things that I really enjoyed reading but they all seemed to me to be related to Descartes assumption that God exists. The assumption that God exists is non important but rather the fact that to follow his argument through Descartes had to postulate a God. Everyone has to decide if they believe in an existence of a God based upon their own life experiences, to just decide on the existence of a God because you are told so is denying the fact that you are a rational thinking being.