Disbelieving something and not believing it are the same thing; the former is simply the language's way of positively phrasing the latter.
Of course there isn't, but that's just as true of leprechauns, Santa, and the tooth fairy. That's no reason to believe in any of the four.
As for your point about the Big Bang, it's just wrong. Causality is a result of spacetime, and spacetime is a result of the Big Bang. Causes did not exist until 'after' the Big Bang. Nothing caused the Big Bang because causes didn't exist.
First, that is an assumption but we know sweet FA about what existed before that Big Bang other than assumptions, but it does make your belief that the Big Bang happened because it did. That the four fundimental forces of the universe (assuming they existed) ceased to unified because they did. If there were no causes, why should there be an effect at all ? Basicly no one knows why the Big Bang should occur. So the concept of an all-powerful being creating it is as valid of it being created by Santa, or the Easter bunny.
The point about beliefs is, there is absolutely no evidence supporting the existence of a God. Therefore, it is not rational to believe in one. Atheism is the rational position, and it is also the natural position--people are born without a belief in God.
I never claimed Atheism wasn't a rational position, just as agnosticism is also a rational position. I would disagree that it is a natural position. The concept of god or gods has existed is most, if not all, civilisations.
It is one of the things Lini is for, taking the blame. She usualy deserves it even if I don't know how.