"I received your letter of June 10th. I have never talked to a Jesuit priest in my life and I am astonished by the audacity to tell such lies about me. From the viewpoint of a Jesuit priest I am, of course, and have always been an atheist. Your counter-arguments seem to me very correct and could hardly be better formulated. It is always misleading to use anthropomorphical concepts in dealing with things outside the human sphere — childish analogies. We have to admire in humility and beautiful harmony of the structure of this world — as far as we can grasp it. And that is all."Four years later, in 1949, Raner wrote Einstein again, asking for clarification: “Some people might interpret (your letter) to mean that to a Jesuit priest, anyone not a Roman Catholic is an atheist, and that you are in fact an orthodox Jew, or a Deist, or something else. Did you mean to leave room for such an interpretation, or are you from the viewpoint of the dictionary an atheist; i.e., ‘one who disbelieves in the existence of a God, or a Supreme Being?’” Einstein responded on September 28, 1949:"I have repeatedly said that in my opinion the idea of a personal God is a childlike one. You may call me an agnostic, but I do not share the crusading spirit of the professional atheist whose fervor is mostly due to a painful act of liberation from the fetters of religious indoctrination received in youth. I prefer an attitude of humility corresponding to the weakness of our intellectual understanding of nature and of our own being."
I agree, and would also add what Noam Chomsky said when asked the same question: what do you even mean by "God" or a "Supreme Being" in the first place? At least the believers in an anthropomorphic personal god have something specific in mind that we can dismiss as a fantasy, but the attempts of sophisticated theists to be more nuanced about it quickly devolve into, uh, poetry (if you're feeling generous), or gibberish (if you're not).
I also pretty much agree with his characterization of the "professional atheist". I personally identify as an atheist because, like he said about the Jesuit priest, I am one as far as the vast majority of my society is concerned. Also, given how much actual, dangerous oppression faces those in many countries who refuse to conform, I think it's important to not take for granted our luxury to be open about our lack of belief, to help destigmatize it. But I don't think religion ever will be totally eradicated, and my suspicion of human nature is such that I can't get truly enthusiastic about what a wonderful world it will be if only it could be. And while I certainly understand the impulse, I can't help but shudder a little to see the sort of tribal mentality that wants to highlight all the examples of those on "our side" -- atheist musicians, actors, and other public figures. I know it can be comforting to be reminded that one isn't alone in holding an unpopular belief, but as is so often the case with politics, it's easy to develop a monomaniacal fixation on such a distinction. Roy Edroso has long been keenly critical of conservatives who subordinate art to propaganda for the party line, disowning entertainers who express heretical opinions, but I've seen quite a few liberals as well who care more about the political beliefs of an artist than the art itself.
So I feel like my atheism is more positional than ideological. I am not on anyone's "side". I have no desire to convince other people to agree with me; I only want to retain enough personal space in which to be free from excessive pressure to agree with them. But I'll also assert myself against those who seem to feel that Einstein's "attitude of humility" is somehow incongruous with open expressions of atheism. I've said before, and I'll say again: in my eyes, agnosticism is a statement about the boundaries of knowledge. Atheism is a statement about the credibility of belief. We can fully admit that we don't know absolutely everything, that we can't see everything from a - ahem - God's-eye perspective, while feeling confident enough to say that we see no reason to believe that our imperfect knowledge leaves a loophole for any metaphysical fantasy we can dream up.