PEOPLE with temporal-lobe epilepsy are prone to religious hallucinations. Two decades ago, this finding led Michael Persinger, a neuropsychologist at Laurentian University in Canada, to try stimulating people's temporal lobes artificially, to see if he could induce a religious state in them. He found that he could. By exposing volunteers' temporal lobes to a weak magnetic field, he was able to create in many of them the sensation of an ethereal presence in the room. (...) The origins of religious experience are one of the most mysterious phenomena in brain science. It would be nice to get a straight answer.