Suppose you’re God: How can you be sure you’re omnipotent? Perhaps you can accomplish anything you can imagine in your own corner of reality—a lucid dreamer can say that much—but there’s some greater reality you’re not even aware of in which, like the dreamer wakened, you’d have no such power. Or maybe even within reality as you know it, there are gaps in your power you aren’t aware of because you can’t even think of the relevant tests. The obvious response is that you’d know all these things because you’re omniscient—but of course, the same problem arises. How do you know you’re really omniscient? At most, there might not be any questions you’re aware of being unable to answer—but that’s hardly the same thing. The subjective feeling of omniscience might in fact be a symptom of a profound ignorance—being unaware even of the existence of those domains of knowledge you lack. How, for that matter, do you know the answers are right? This is a particularly thorny problem when combined with omnipotence: If reality is whatever you decide it is, does it even make sense to speak of true or false beliefs? Beliefs, after all, are supposed to be true or false of an independent reality.
I am not, of course, a believer, but if I were, I’d prefer to imagine a deity occasionally plagued by these thoughts—an agnostic God who sometimes doubts Himself.