I just received this little query on Formspring, and rather than waste a somewhat detailed answer there for two people to glance at, I figured I’d post it here, instead [original question edited for spelling/grammar/coherence]:
Here's my question, Joé: How can anyone who considers himself a rationalist be an atheist? Philosophically speaking, atheism is the weakest stance one can take in terms of pure logic. YOU CAN'T PROVE A NEGATIVE.
I don’t think you understand what rationalism is. It means the rejection of any beliefs that aren’t supported by credible (logical or empirical) evidence. Now, given that the existence of God(s) is typically implied to have some relevance to our natural world, it thus stands to reason that it can be subjected to critical analysis. And given that there is absolutely zero credible evidence to support the existence of God(s), the only rational conclusion is that God(s) just doesn’t exist (or else that if he does, his impact on the natural world is so minute that it isn’t even worth considering).
Also, I never claimed that negatives can be proven; quite the opposite, in fact. No atheist has proven, and nor can they truly know, that God(s) doesn’t exist. They simply don’t believe that he does. (And those who, like me, actively believe that God(s) doesn’t exist are more accurately labeled “anti-theists”, but that’s mostly just splitting hairs as all non-theists are basically in the same camp, anyway.) It comes down to the old distinction between agnosticism (which is about knowledge) and atheism (which is about belief); ergo, all reasonable atheists are also agnostics (despite the popular and ill-founded resentment towards that label).
In the end, atheism in and of itself really has little to do with philosophy. At it’s basics, it’s limited to asking whether there’s any good reason to believe in God(s), and if not, then why do so. Anything more is really just details, and philosophical battles on the matter are mostly triggered by anti-atheist critics who just can’t seem to understand that people can live just fine without believing in any one or more deity(s).