ELL, what did you think it was?  Let me guess.  You thought it was about not believing–and naturally not believing something is the opposite of belief.  And since the opposite of belief is fact, well there we are.

Of course atheism is just a belief.  One of my favourite websites says it best:

Strictly speaking, atheism is an indefensible position, just as theism is indefensible, for both are systems of belief and neither proposition has been (or is likely to be) proven anytime soon.

The rational position for the non-believer to take is to say that there is almost certainly no god, because no credible evidence exists to support the claim that god exists. This is a stronger position than agnosticism, which holds belief and non-belief on an equal footing.

So the debate between atheism is about the evidence and not about the status of propositions.  Oh, and what beliefs are in…