To be fair, I did not state that atheism is a religion, I've only stated that the definitive statement "God does not exist" is not a provable claim. Therefore it is a statement of belief, much like the statement that "God does exist". Basically I've pointed out the similarities between the two camps that are trying to definitively state an answer to a question where no answer is known. For both it's a matter of opinion although often both sides don't seem to feel that way. As for your gumball example I fail to see the distinction. If I think there's an even number of gumballs and you state that I'm wrong- well that is the same as saying there is an odd number of gumballs- which you don't know either. Now if you're just saying "I don't think you know that there are an even number of gumballs, I just think you're guessing" well that's the equivalent of agnosticism. I've always felt, and a quick google confirms, that atheism is the belief that God does not exist.