Why do you believe that there is no god if you do not know? Explain your reasoning.
It is illogical to believe without knowing. To know but not believe. If you are illogical then there is no point in having an argument with you.
There are a variety of claims God does or does not exist. Dogma, intuition, logic. But the problem with logic is there is no solid evidence to prove or disprove. (There is our agnostic!)
Quite simple: I do not believe that God exists, but if what I think would be sufficient evidence for his existence, I'd probably change my mind (probably being there for not even I can predict my own thoughts).
To take it in another context:
Annie believes that the world is about the size of Madagaskar, where she lives. However, she knows that some people believe that there is something more than just this one big island and she'd be willing to believe them if there was any viable proof.
Scenario A: No proof is brought fourth, Annie continues to believe that the world is about the size of Madagaskar.
Scenario B: Proof is brought fourth, but Annie rejects is or by logic, faith, etc, continues to believe that the world is about the size of Madagaskar.
Scenario C: Proof is brought fourth, Annie accepts it and now believes that the world is more than just Madagaskar.
This is a bit more earthly example, but if you consider that the proof can be a bit of flotsam from a kind of tree that doesn't grow on Madagaskar (which can be either dismissed or interpreted as a sign) or a gigantic cruise ship crashing into the village (kindof hard to deny it then, the athiest-theist version would probably be equal to God's hand sweeping down and smacking sinners or something) or something else.
The difference in this fictional story is of course, it is proven that Annie is wrong and I don't think that anyone would disagree on that, theist or atheist alike.