The whole point of implicit (majority) atheism is that we can only be sure about inherently contradictory claims. I can, and do, no more reject the very minute possibility of disinterested, inconsistent, malevolent, or sure you're right just flat out ineffable God-Above-Gods than I reject the idea of there being 18' tall tripedal bright blue aliens in the Crab nebula who communicate only in falsetto iambic pentameter.
I accept none of these claims, as none have the slightest evidence in their favor, but I reject none also, as I have no way to prove their falsity. I simply withold belief until presented with convincing arguments. I still lack belief in even non-theological theism if you want to stick with Tillich, and for very much the same reasons. Tillich presents a different argument from Anselm's - but he provides no more reason for me to believe it.
Serious question by the way as you doubrless know this stuff far better than I - how exactly does Tillich justify the Bible as a valid source of systematic theology rather than other holy texts? From my long ago and hardly favorable reading, he seems to just take that as axiomatic.
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