Have you ever heard of exorcism? It’s a stylized ritual in which rabbis or priests try to drive out the so-called invading spirit. It’s pretty much discarded these days, except by the Catholics who keep it in the closet as a sort of embarrassment. It has worked, in fact, although not for the reason they think, of course. It was purely the force of suggestion. The victim’s belief in possession helped cause it. And just in the same way, this belief in the power of exorcism can make it disappear.
