But I believe I’ve seen the real thing. Assaults upon individuals are classified either as “demonic possessions” or as the slightly more common but less intense attacks usually called “oppressions.” A possessed individual may suddenly, in a type of trance, voice statements of astonishing venom and contempt for religion, while understanding and speaking various foreign languages previously unknown to them. The subject might also exhibit enormous strength or even the extraordinarily rare phenomenon of levitation. (I have not witnessed a levitation myself, but half a dozen people I work with vow that they’ve seen it in the course of their exorcisms.) He or she might demonstrate “hidden knowledge” of all sorts of things — like how a stranger’s loved ones died, what secret sins she has committed, even where people are at a given moment. These are skills that cannot be explained except by special psychic or preternatural ability.

I have personally encountered these rationally inexplicable features, along with other paranormal phenomena. My vantage is unusual: As a consulting doctor, I think I have seen more cases of possession than any other physician in the world.