Commandments.

Every once in a while a film fantasy comes along that truly works; but, by and large, fantasy is the hardest genre to pull off. Which is not to say that most movies in which a ghost or an angel returns from the beyond to help a beloved mortal find happiness won't flourish at the box office: cozy, sentimental religiosity of the bogus kind goes over big. But art it is not.

The latest such piece of arrant trumpery is Commandments, written and directed by Daniel Taplitz, who ought to be ashamed of himself: he has combined the Biblical stories of Job and Jonah, and turned them into a comedy-drama that is neither genuinely comic nor especially dramatic. And the religious posturing is saved from offensiveness only because it can't begin to be taken seriously.

The story concerns Seth Warner, a young man who loses his beloved wife, Karen, when, while he snoozes on a sunny beach, she somehow drowns in a calm sea. Next, his house is destroyed in a pinpoint cataclysm, while all other build- ings remain untouched. Even his dog gets it -- not quite in the neck, only in the leg, canicide being taboo in the American cinema. That is the last straw. Seth, the son of good Jews, rebels against the Lord. Even being partially struck down by lightning doesn't stop him: he proceeds systematically to break all ten commandments, ticking them off one by one on a handy piece of paper he always carries about with him.

He is greatly assisted in his pursuit by being taken in by his sister-in-law, the beauteous Rachel. She is married to the worthless Harry Luce, an unfaith- ful, amoral brute who boasts of breaking half a dozen commandments daily and getting away with it. I shan't bother you with the details of this pious con- coction, but will set you at peace by assuring you that all ends well. For having taken his Karen, God rewards Seth with her sister, Rachel, happily an exact duplicate, played by the same actress. For Seth, she leaves the dastardly Harry, who, however, gets to deliver the film's wry narration, which may portend eventual salvation even for him.

Especially annoying is the wasting of three fine acting talents. Aidan Quinn, though we may weary of those oceanic blue eyes overflowing his inverted-isosceles face, is a decent Seth; the refinedly sexy Courtney Cox is a beguiling Karen - Rachel; and best of all is the Harry of Anthony LaPaglia. The Australian-born actor is equally good at drama and comedy, on screen and stage, in masterworks or (as here) trash, and should be cast much more often.

Wasted, too, is the superb Po- lish cinematographer Slawomir Idziak, whose work combines sensuousness and lyricism in the most unassumingly penetrant manner. Watching such winners toil on behalf of Daniel Taplitz makes it hard for the critic not to break at least one commandment, number six.