Atheism is simply non belief in a god. It doesn't 'ask' for anything else. It's like calling someone a theist and expecting then to think, believe and act the same as every other theist.
Aa such they are philosophically diverse. There is just no recourse to a god in that thinking.
It is the active belief that there is no God, based either on faith or on a lack of empirical evidence. But whether God(s) exist(s) or not is currently unprovable... so you're participating in an active belief.
You can be
agnostic and accept that you don't know either way and not be particularly concerned about it... or you can identify as an atheist and be "certain".