The reason why I agree with the dictionary definition of atheism is because I don’t have a positive belief, or an actively held disbelief in all the possible things one could imagine. I don’t disbelieve in The Great Big Gig in the Sky just as I don’t disbelieve in the next imagined deity or supernatural being that someone else supposes to exist. Were not believing in something the same as believing a thing to not be real (hence forth a disbelief) I would have a disbelief (believing a thing not to be) in all the various imaginations possible. Do I have a belief that Carl Sagans Garage Dragon does not exist? Of course not! I don’t have any reasons for not believing in this dragon because I don’t need to maintain why I don’t hold the positive belief in it. I don’t believe in magical Hermitages, Dryads, or the Lochness monster, either. If I had a belief that these things are not real, wouldn’t I have a clearer conception of each thing is disbelieve in? The various imaginations of Big Foot is a good example. Would I not disbelieve in each version of the same myth? I don’t believe in the Volcano god form of Jahovah, just as I don’t believe in the extra-universal, personal saviour version. I don’t have a belief for each of these things not existing, and I don’t need to have fully fleshed out evidences or arguments against them because the default position is not believing in them. Just as Reg posited, I’m not a non-stamp collector; it’s the default position. Were most people engaged in the collecting of stamps, however, I might then identify as a non-stamp collector, but it still wouldn’t be my hobby and collecting stamps wouldn’t not-be-a-hobby.