From Vincent Canby's April 22, 1969 review in the New York Times:
Pier Paolo Pasolini's "Teorema," which opened yesterday at the Coronet, is the kind of movie that should be seen at least twice, but I'm afraid that a lot of people will have difficulty sitting through it even once. At least there were some who had that problem Friday night when the film was given an unannounced preview at the Coronet, supplementing the regular program, headed by "The Prime of Miss Jean Brodie."Can you imagine a theater today showing an unannounced preview after the feature? Or showing Pasolini at all? I still have a raincheck ticket in my wallet from the Coronet [aka the Baronet Coronet, aka the Coronet I & II, which was demolished to make way for an Urban Outfitters] to go back and see Dancer In The Dark. I went to a noon showing, only to realize I was crazy and had a call at like 2pm, so I left before the trailers ended. Oh wait, I just pulled it out. The ticket was from the Cinema 1,2,3,4 up the street. Never mind. The Pasolini thing's still crazy, though.It was a disastrous combination. "Baby Love" is a straightforward, skin-deep narrative movie that elicits conventional responses to familiar stimuli. "Teorema" (theorem) is a parable, a movie of realistic images photographed and arranged with a mathematical precision that drains them of comforting emotional meaning. For the moviegoer whose sensibilities have been preset to receive "Baby Love"--or just about any other movie now in first run here--"Teorema" is likely to be a calamitous and ridiculous experience.
...
There is very little dialogue in the movie--923 words, say the ads (but I'm not sure whether this refers to the Italian dialogue or the English subtitles). Even though Pasolini is a talented novelist and poet, the film is almost completely visual. The actors don't act, but simply exist to be photographed. The movie itself is the message, a series of cool, beautiful, often enigmatic scenes that flow one into another with the rhythm of blank verse.
This rhythm--one of the legacies of the silent film, especially of silent film comedy--was impossible for the Coronet audience to accept. The seductions are ticked off one after the other with absolutely no thought of emotional continuity. So are the individual defeats, which are punctuated by recurring shots of a desolate, volcanic landscape swept by sulphurous mists.
There is also a kind of rhythm within the images. Someone seen in right profile is immediately repeated in left profile. An action that proceeds to the left across the screen may be switched 90 degrees, directly away from the camera, or into the camera. Early scenes are in black and white. Later scenes are so muted they almost look like the old Cinecolor process, only to go monochromatic again at the end.
Theorem (1968) The Screen: A Parable by Pasolini: Teorema' in Premiere at the Coronet Terence Stamp in Role of a Visiting God [nyt, via sal mineo's ghost, thanks ready for the house]