That is the question:
How does one tell the difference between hearing the Voice of God, and the onset of paranoid schizophrenia?
Well, that’s the crucial question now, isn’t it. But in the aforementioned case of Elisha and Elijah, I think that seeing fire come down from Heaven and incinerating dozens of priests of Baal would likely serve as sufficient proof to even the most precariously balanced or skeptical minds that they were not, in fact, delusional.
There’s no question that God understands our doubts. Jesus Christ was not only sympathetic towards his dubious friend Thomas, but he specifically said that talk was cheap, hence the miracles.