SUSAN Sontag's Brother Carl is so much more accomplished in every way than her earlier Duet for Cannibals that it is liable to be mistaken for a good film. It is not quite that. It is what you might better call an imitation of a good film, a kind of master forgery, the film equivalent of painting by numbers, the sort of product that looks all right until you stick it next to the real thing.

Unfortunately, this week at the Brattle Theater, it is stuck next to the real thing--Bergman's The Passion of Anna. Ingmar Bergman is one of Sontag's very favorite directors, and that judgment is much to her credit. But if you happen to see both films in the double bill, you will quickly understand the difference between the original artist and derivative craftsman.

It is not that Ms. Sontag is a thief, it's simply that she's a critic. She has seen so many films and thought so long and hard about them, that her own look like a composite of all those things she's praised in others. Duet for Cannibals was made out of Bresson and Bergman and Godard in equal measures, one ingredient at a time. It substituted confusion for narrative and vagueness for thought. It was the type of film that gave the avant garde a bad name.

Brother Carl takes at least a dozen steps in the right direction. That leaves it still some distance short, but it is certainly a beginning. Sontag has reduced her influences to Bergman alone here. She has made concessions to coherence of plot and plausibility of character. She has this time made a film that can be sat through.

BROTHER CARL has to do with a young Swedish woman named Karen who is suffering from an acute case of bourgeois angst and so decides to separate for a time from her lawyer husband and retarded child. She goes with a friend Lena to the island home of Lena's ex-husband Martin who spends his time caring for a once brilliant dancer named Carl now deeply scarred by his former devotion to his art.

Martin and Lena trade bitter insults, Martin and Karen have an affair, Lena seduces Carl who in his thirties was still a virgin, then Lena drowns herself. And so on and so forth, etc., etc., etc.

At the center of the film and by far the best thing in it is the figure of Carl. He is a kind of blessed innocent who lives out of doors and can go weeks without talking. He is terrified of sexuality and baffled at the unhappiness of the others. After Lena's suicide he is stricken with guilt and determines to work a "miracle" to prove that things need not be the wretched way they are. He returns home with Karen and in the film's last scene he works his miracle, teaching her mute child how to speak.

There is much emotion expended in Brother Carl, much screaming and wringing of hair, many expressions of anguish. And it almost catches hold, it is almost infecting. But somehow the emotional intensity is curiously disembodied when it counts most. Those are people there and the things in their eyes look suspiciously like tears, but they are really no closer than ants in a bottle.

Part of the problem is that for both her films Sontag was forced to go to Sweden to find financial backing. She shot her film there with Swedish technicians and a predominantly Swedish cast; she does not speak Swedish. That is a difficult hurdle, and she has not come close to surmounting it.

MUCH more serious, though, is that Susan Sontag still appears to be one of those people more interested in Making Movies than in making a particular movie. She has no religious anguish to purge, no personal vision to express, no political axe to grind. This makes for wonderful objectivity, but it also makes for emotional sterility.

Sontag came to prominence in the middle sixties as a radical critic of culture, spokesperson for the New Sensibility. The New Sensibility praised form and damned content. It was against interpretation and for an anesthetic revolution founded on the non-literary arts of music, painting, film and architecture. In its pantheon were Jasper Johns and John Cage, Roland Barthes and Jean-Luc Godard, Buckminister Fuller and Alain Robbe-Grillet.

The New Sensibility is old hat now. Its promised revolution may or may not have occurred, it hasn't made any difference one way or the other. The cultural tide has gone out once again, and the sixties' avant-garde lies gasping on the beach. That is in its way unfortunate, but at least one encouraging development has grown out of the demise. There are now stirrings of a new political consciousness in the resolutely political avant-garde of the last ten years. So Jean-Luc Godard renounces the bourgeois art that won his reputation, and in the current issue of Partisan Review Sontag has an article on feminism that is more passionate and convincing than any of the novels she's written or films she's made. Change in artistic form is understood as necessary but not sufficient, politics is recognized as the true base of cultural change.

THIS is the New England premiere of Brother Carl, but already it is something of a museum piece. It is a relic of the New Sensibility and suffers all the limitations of that movement. It is an art-product that refuses to ground itself in this world at this time, and so its emotion is emotion echoing in a void.

I find that I cannot quite recommend Brother Carl, there are too many better movies in Cambridge this week. But go see Hail The Conquering Hero and Jules and Jim and Rules of the Game and The Passion of Anna, and then if you are still keen on movies, go see Brother Carl.

Susan Sontag will probably never find her way into artistic significance. Not many people will read her books, and not many will watch her movies. But she has her function nonetheless. She is thinking all the time and she rides the crest of every new fashion; she is worth keeping an eye on. When the cultural wind shifts, she rustles in the breeze.