An atheist is someone who never takes the existence of any supernatural entity into account in making any decision. Once I decide that gods will play no part in my life, it makes no difference that I cannot "prove" that decision correct to anyone else's satisfaction. It is enough to make me an atheist that I cannot be proved wrong. Proselytizers need to worry about proof; agents don't.

I consider myself a non-proselytizing atheist. I have no interest in persuading anyone about any theological issue, other than whether a supernatural entity wishes me harm. On that question, because I never take the existence of such an entity into account, I place the burden of proof regarding such an entity's enmity on anyone who asserts it. Others may put that burden of proof on me. But there is no a priori reason the burden of proof should be on either of us. As Sr. Arellano says, that choice is for each of us to make.