Anyone who professes absolute certainty that God doesn't exist (or that he does exist, come to think of it) is misguided. God's existence has been placed by his adherents, quite deliberately, beyond the scrutiny of science, therefore it isn't possible to say that he certainly doesn't exist. It is possible to say that, by all application of logic, evidence and reason, the probability of his existing is vanishingly small. That's as good as it gets for a thinking atheist, and it's pretty good. If you want to call us atheists agnostics at the far end of the spectrum, I won't argue. Or you could say that an atheist is an extreme agnostic. We all know what we mean. I've never liked "atheist" because the word defines us within the context of a ludicrous and misguided notion, God. I prefer be defined within a logic and evidence-based context, though I may fall short of the ideal myself.