Why Is Anybody Convinced There Is A God?

Well, it still wouldn't make sense to talk about present mental phenomena, qua present mental phenomena, as an illusion, because what we're talking about in that case are appearances as such. The appearances can't be getting something else wrong, because there is nothing else that they're representing.

However, it doesn't do anything for the logical possibility that all perceptual data are illusory. But that's all that is--a logical possibility. There's no reason beyond that to believe it. And there are contradictory logical possibilities.