"how do I know something that doesnt exist, doesnt exist."
i think it'd be more "how do I know something that I don't know wheter it exists or not, doesnt exist."
There is no evidence for God's existence, and there is no evidence for god's non-existence. What does that leave? Speculation, basically.
It's kinda useless to debate about something that is pure speculation. Speculating itself can be interesting tho.. it's just that it never really amounts to any concrete conclusion... which is fine.
If someone want's to believe something that isn't proven either way, well that's their choice, but neither I nor you can prove or disprove them... just like they can't prove themselves either. But let's not forget that sometimes we experience something that we can't replicate or cant demonstrate, then it becomes a subjective truth, that you only know true but can't prove. It's useless to try and prove something like that.. all you can do is try to put that experience in words and hope that the people you're talking to are open enough to think it's possible, but of course the other people need to experience it too in order for it to be true to them also.
As for believing. Well strong atheism is a belief, it's the belief that god does not exist, and I find it's just as unjustified as theism. However you can be agnostic-leaning atheist (weak atheism) and that just means that you have a penchant that there's no god but remain open to other possibilities until one way or another is proven... it's a bit more logical when no evidence for either side exists. There's nothing wrong for not siding on a side, it's the best way of being both receptive and logical.
