However, there are all sorts of behaviours in the Bible that might be called mad now, but aren't designated as insanity by the text itself. People see visions — of angels going up and down ladders, of fiery chariots — and, like Moses, who hears a bush talking, and Balaam the prophet who has a conversation with his donkey, they hear voices of those who cannot be said to be present in any usual sense of the word. They also speak in tongues, as the disciples do at Pentecost. Like madness, the visions, the voices and the speaking in tongues are due to external and usually divine agencies. In a world so permeated with supernatural powers, there are no accidents, and in one so riddled with prophets — who went into a frenzy while prophesying — many more kinds of behaviour were accepted as normal, at least for a prophet or an inspired person, than would be the case now. John the Baptist, dressed in animal skins and wandering around in the wilderness denouncing his social superiors, was not thought of as a de-institutionalized street person who's gone off his medications, but as a saint. And this was the pattern for mediaeval views of aberrant behaviour — if you were acting crazy it was a divine punishment, or else you were possessed, by powers either divine or demonic — perhaps aided, in the latter case, by witches.
Margaret Atwood