In a posh neighborhood outside Copenhagen, a cult of middle-class deserters, living in a large, unfurnished house, act out their alienation by pretending to be mentally impaired. They go off to, say, a public swimming pool, and one of them will begin to ''spaz'' -- to enter a trance state, body contorted, face caught in horrified mid-gawk as he blurts out some antic, impolitic (and deeply true) observation to the shock and dismay of the tranquilized suburban drones around him.
If ''The Idiots'' were simply a merciless, ''let's ridicule the retarded'' provocation, the film would have been despicable. But Von Trier, less bad boy than flower child, is too sentimental for that. His roving commune of the fake impaired isn't out to be cruel. Each one is trying to get in touch with his or her own ''inner idiot'' -- with the pure, sad, broken child lost behind the bourgeois facade. It's primal therapy for a technological age in which intelligence itself has become an enslaving, homogenizing force.
This director, in other words, is replaying the guerrilla-theater spirit of the '60s, but with the cleansing psychodramatic mysticism of a digital-age Ingmar Bergman. ''The Idiots'' is a raw, funny, maddening ramble. Von Trier seeks catharsis by pushing everything to extremes. He even stages an orgy featuring full-frontal nudity (with the naughty bits covered by black bars for the U.S. release). There's a danger that he may come to see filmmaking as a put-on, yet he has a rare and potent gift for channeling our inner neurotic frenzy. At the end of ''The Idiots,'' one of the more shy cultists goes home to confront the members of her family by ''spazzing'' right in front of them, and it's a gripping moment of high torment. Von Trier may be a bit of a fruitcake, but at least he means what he does.