Should Atheism Be Provisional?

There's been a minor dustup here in atheist town. The subject of "what could possibly convince us of the existence of god(s)" has bubbled to the fore again. The last time this was brought up by Greta Christina, I commented, saying that technologically advanced aliens would be a more parsimonious explanation for the types of evidence she suggested. (I didn't mention it at the time, but so would human beings with a new and highly advanced technology. There's nothing to say there won't someday be made a discovery on the level of splitting the atom that will give humans "godlike" powers. In other words, a heretofore unknown technology indistinguishable from magic doesn't have to be extraterrestrial in origin.)

Currently, the conversation is bouncing back and forth between P. Z. Myers (here, here, and here) and Jerry Coyne (here). Greta Christina has also made a follow-up post, clarifying her position and acknowledging the "aliens" angle.

While Coyne and Christina are taking a firm "provisionalist" stance (i.e. that their atheism is provisional and could in principle be overturned by new evidence), Myers takes the opposite view. He's basically saying that the concept of god is so wooly and useless that there can never be convincing evidence for it. This stance has drawn accusations that he's making irrational a priori assumptions, and that his atheism is just as faith-based as any religion.

I think this unfair. Personally, I mildly disagree with Myers - I think I should be openminded to the possibility that there might be some kind of evidence that could convince me of god(s), even if I can't imagine what it is. However, calling his position irrational and faith-based is totally uncalled for and off target.

Even the most hardline sceptic has beliefs that cannot - even in principle - be overturned. For one example, there's no possible evidence that you could ever show me that would convince me that I don't exist (or that the universe doesn't exist, etc). As sceptical as I am, that's something that I will always believe, no matter what. Is it an irrational position taken on blind faith? No, it's just an extreme example of "extraordinary claims require extraordinary evidence." There are just some claims that verge on infinitely extraordinary, and no one can muster infinite evidence.

Perhaps the nonexistence of god(s) is in the same category as the existence of the universe. Totally unassailable at this point, considering the overwhelming and persistent evidence.

In principle, I'd side with the "provisionalists", but I don't think Myers' position is ridiculous on the face of it. He makes (characteristically) good points.