There is no strict categorical distinction between pornographic and non-pornographic fictional movies. The most useful definition of filmed pornography is a work made with the intention that the audience will masturbate while watching it; the graphicness of the sex simply serves that end. This intention does have an enormous practical effect: does anyone with XXX discs at hand pop Basic Instinct (1992) or Wild Things (1998) into the DVD for a five-minute whack before work?

At the same time, people have always derived private "pleasure" of whatever kind they choose while thinking about certain Hollywood stars they've seen in movies. Rudolph Valentino, Clara Bow, Clark Gable, Jean Harlow, Jane Russell, Rita Hayworth, Marilyn Monroe, Robert Redford, Raquel Welch, Brad Pitt, and Angelina Jolie would scarcely have had the careers they've had if this weren't the case. It breaks down to a binary distinction: supposed non-pornography is no more than any movie the makers do not intend you to masturbate over while watching it.

Bruce LaBruce's The Raspberry Reich (2004) crossed this non-existent line by mixing hardcore sex with political satire of western terrorist cells. (His approach was like the Marquis de Sade's in Philosophy in the Bedroom — alternating genres in order to turn you on to the characters' ideas, despite yourself.) John Cameron Mitchell's Shortbus crosses the same line, but starting from the other side.

Shortbus interweaves the stories of three New York City couples with sexual-emotional dysfunctions — i.e., it's a "relationship" movie — but it begins with explicit scenes of the characters having sex. There's full nudity, wood, real in-and-out, and cumshots, all the bits you usually don't see at the movies, from nuts to soup. These interludes are not shot in such a way that you wish you were at home and more "comfortable," however. Mitchell worked with the actors to develop the characters and storylines and the sex is tied directly to what they came up with. In other words, the sex is "justified."

Probably too justified. The problem with explicit sex in a supposedly realistic work of fiction is that the sex is almost always too emphatically informational. In movies, I have never seen anything else that approached Bernardo Bertolucci's Last Tango in Paris (1972), in which the characters hole up for a three-day sexual escapade. They indulge fantasies, which turn out to be decidedly unsustainable once the demented holiday ends; there's no road back to daily living, not together. In Last Tango the emphasis is warranted because it's about a man acting out his conflicts in sex games, and the conflicts are developed with a minutely realistic acuity. And it can't be called naïve because it dramatizes the limitations of those games.