WHITE RAVEN. Music by Philip Glass. Libretto by Luisa Costa Gomes. Directed by Robert Wilson. With Lucinda Childs, Ana Paula Russo, Janice Felty, Herbert Perry and Vincent Dion Stringer. American Composers Orchestra and White Raven Opera Chorus conducted by Dennis Russel Davies. Attended at Tuesday's premiere. New York State Theater, Lincoln Center. Presented by Lincoln Center Festival. Repeated tonight through Saturday.

IT'S BEEN 25 years since Robert Wilson and Philip Glass made their reputations with the mammoth, mystifying and now classic opera "Einstein on the Beach," which distilled the genre to its abstract essence: objects, light, movement, song and sound. Now, with "White Raven," they have returned to Lincoln Center, fortified with a sense of their place in history and the license to think bigger than ever.

At the behest of the Portuguese government, which commissioned the opera, "White Raven" deals with the exploits of the 16th century Portuguese explorer Vasco da Gama, but also, more grandly, with seekers of all kinds and in all times. But it also represents only half of a vast, still uncompleted, operatic diptych. The other part, according to Glass' program note, will treat "the civilization and development of Islam from about 1000 A.D. to 1500 A.D." Why stop so early, I wonder?

The problem with an opera about everything is that it doesn't matter much what's in it. "White Raven" contains no characters, only emblems, singing stick figures with nothing to express. It has no plot, only roving allusions. Judy Garland's Dorothy and the Tinman wander into the exploits of da Gama - why? Oh, yes, because the Portuguese explorer and the girl from Kansas both have their eye on somewhere over the rainbow, but also, surely, because the ploy provides an irresistible opportunity for camp nostalgia.

Wilson's work is always permeated by wistfulness - for a time when surrealism was the latest thing, when cute meanderings a la Gertrude Stein still struck people as outr, when music videos had not yet harnessed all Wilson's techniques. Back-lit fantasies, period- pastiche garb, dreamy non sequiturs, mechanical dance - by the 1980s these had become the stuff of commercial music television. Even Glass' musical style has become a product, its repetitions endlessly recycled and comfortingly familiar. And so, "White Raven," half of it wordy the other half wordless, glides along the surface of its images, carried by the soothing burbles and incantations of Glass' score.

The second half begins with a storm at sea. Chains of flat, triangular waves bounce stiffly up and down. Behind them, giant, disembodied limbs - a naked leg, a grasping hand - bob in the storybook brine. Pornography is accused of reducing human beings to their body parts, but nobody de-personalizes people more dispassionately than Wilson. It hardly makes any difference who sings what. The only purpose of using a live cast, rather than, say, animated holograms, appears to be to provide figures on which to hang Moidele Bickel's costumes.

Granted, those are ravishing and fantastical: a pair of gilded Siamese twins who share a double-wide farthingale, an Inca prince daubed rain-forest green, an unidentified tribesman with one elephantine foot, assorted stock street-theater characters, a brace of human-size ravens with giant mesh heads and beaks, an ivy-covered dancer, a beauty-pageant winner in a spangled gown, a reptilian soprano with glowing dragon-head and fetchingly spiked tail.

Singers, dancers and orchestra fared well at the U.S. premiere, but the mechanical performers proved more capricious. A curtain refused to descend until manually yanked, the amplification system made even deeper murk of Lucinda Childs' narration and a lighting glitch caused an impromptu 10-minute pause. Perhaps that's what you get for creating an opera about human history and leaving out the humans.