The fact that we haven't had any proof doesn't mean it's not there waiting to present itself. If I were a betting men, I'd say it probably, most likely - means it's not there. But if he showed up tomorrow, it would certainly put my skepticism to rest. How would I be sure? Well... If that were true, then sculptor would indeed be correct - that nothing could sway a skeptic, no matter how compelling. And that would be a very dark day indeed for skepticism. Just as theories must be falsifiable, so too, some concepts must be verifiable. There must be a litmus test it can pass, or we stand - not as skeptics - but as true, dyed-in-the-wool (non)believers. No, there is certainly a threshold beyond which I would accept that it is God that is before me. It would be a pretty high threshold, but so what? Any number of tricks such as turning the planet inside out and putting the sun in a bell jar at its center, all without harming anyone, would be trivial for God. At that level of ability, God would quite conceivably be more plausible than spectacularly-advanced magic.