Though nobody expects biannual exhibits of contemporary art to be qualitatively consistent, the one now at the Hirshhorn Museum and Sculpture Garden is dumbfoundingly uneven. "Directions 1986" attempts to spot two trends -- "Painting Into Nature" and "Toward the Baroque" -- but that is not its chief division: When it's good it's very good and when it's bad it's horrid.

First the good news:

The exhibit brings to Washington four new paintings by Frank Stella from his "Cones and Pillars" series. Those of us who place him with the toughest, most original of abstract art's inventors will find our high opinions here amply confirmed.

That the art of Robert Morris, the exhibit's other star, is comparably triumphant comes as a surprise. Morris, 55, is a problematic artist. A painter and a sculptor, a conceptualist, a Dadaist, a Minimalist, a dancer, he's been known to flirt outrageously with apocalyptic politics and operatic drama -- and occasionally with hokum. Objects he has shown here, stunning at first sight, later disappointing, have fooled us in the past. But here, as if reborn, he's put it all together. He is showing four baroque assemblages from his "Burning Planet Series." Ordered yet chaotic, searing yet exalted, these visions of the planet's end take the breath away.

Rarely has the Hirshhorn shown new objects of such power. The two galleries devoted to Robert Morris and Frank Stella justify repeated visits to "Directions 1986."

Now the bad news:

The first half of the exhibit, "Painting Into Nature," is embarrassing. An accompanying handout says this section of the show "investigates a return to a kind of subject matter that has been virtually absent from progressive American art since World War II." The Hirshhorn's Phyllis Rosenzweig, the associate curator responsible, also credits these four painters with a "return to themes of nature."

Where has she been living? Artists in America have always painted nature. Think of all our Wyethites. Think of our photographers. How artists deal with landscape is a theme well worth exploring, but Rosenzweig's selections do not do it justice. She might have taken clues from the little landscape survey now on view at the Corcoran, a far more telling show. Or she might have chosen pictures by Wayne Thiebaud, Vija Celmins, Joseph Raffael, Neil Jenney, John Alexander, Joe White or a dozen other inventive landscape painters. These, at least, are pros.

The four nature painters she's selected seem, in contrast, amateurs. They are Alice Fellows, Melissa Miller, Yolanda Shashaty and Washington's Peter Fleps.

A number of these painters borrow from their betters. Fleps, for instance, who mounts his modest little landscapes in huge and ill-made frames, is a sort of mini-Neil Jenney. Fellows is comparably shameless: Her leaves and fronds and gorges look like awkward, muddy steals from Georgia O'Keeffe. Miller's art is friendlier. She paints her gaudy pictures of bear and deer and jack rabbits with an illustrator's verve, but her colors are all wrong. Her bear aren't stalking salmon, but green-headed goldfish; her deer seem to be dancing under mercury-vapor lamps. Her fantasies, writes Rosenzweig, "recall the exuberance of the Flemish Baroque of Peter Paul Rubens." Mark Trail is more like it. Shashaty's seascapes are not so offensive. They do suggest a dream of seas, but their surfaces are mushy, and they're nothing to write home about.

To experience just how bad the exhibition is, stand there in the Stella room and look past his bright relief, "Giufa e la statua di gesso" (1984), toward "Gorge" by Fellows on the wall beyond: He humiliates her art.

Many abstract painters nowadays yearn for safety. Comforted by limits, they contentedly refine this small idea or that one within the tight confines of their familiar little worlds. But Stella tests the limits. With a willingness to push it that approaches the ferocious, he forges on and on.

Stella's art is daring, taxing and complex, yet no living abstract painter has so many fans. Rosenzweig says that she is "glad to be living at the same time he is painting," and she is not alone. There are many in the art world who watch for his inventions with as much anticipation as they once awaited new LPs by the Beatles. No one who has watched him since 1958 has been able to predict what move Stella would make next. And yet each step, once taken, seems comprehensible in retrospect. The seed was there before. Why did we not see how that seed would grow?

His "Cones and Pillars" pictures -- with their gestures and their juttings, their interrupted arcs and illusionistic scrolls -- may startle at first sight until one discovers how many of their elements were prophesied succinctly by Stellas of the past. The lines of black and white and the edge-obeying parallels found in these new pictures recall his first "Black Paintings" of 1958. His "Protractor" series, too, is suggested by these sweeping curves and bright, surprising colors. We know that Stella has been moved by Abstract Expressionist brushwork, by the acid-bitten etching plate, the expansiveness of Rubens and the space of Caravaggio, and all of these concerns are acknowledged in this art.

Someday we will see a full Stella retrospective. It will be a mighty show.

A Robert Morris retrospective may, in contrast, prove confusing. A number of his early pieces -- his cubes of mirrored glass, his works of steel, felt and steam -- seem a little shy of substance now. It is clear that he loves theater, but some of his performances -- his notorious self-portrait in chains and Nazi helmet, or the skeleton-and-motorcycle combine he once showed at the Hirshhorn -- were in some ways thin as stage sets. His "Burning Planet" pictures may someday disappoint as well. But they seem awesome now.

They are vast in size and spirit. Their references include light-filled Baroque churches, Star Wars and holocausts (that of World War II and one that may yet come). These objects speak of death. And yet they entertain. Without slipping into foolishness, they somehow call to mind the fun house and the graveyard and the Disneyland exhibits.

Three of these large objects contain oil paintings, fiery abstractions filled with light and space. The fourth presents instead a pair of warped, distorting mirrors -- mirrors flecked with stars. But something here is new. The frames around these images are at least as important as the pictures they enclose.

These frames were cast from troughs of clay into which the artist carefully embedded bones and human skulls, fetuses and faces, penises and fists. Baroque painters fringed their canvases with gilded leaves and tendrils; Morris surrounds his with the detritus of humanity and with relics of our violence.

A variety of objects have been placed before these pictures. In the one that he calls "Order," a sort of heavenly drapery, recalling those that swirl around the loins of the Christ in 17th-century paintings, floats before the canvas like a kind of benediction. A skull, a fist, a giant eye, a penis and a clawing hand tear across the mirrors of the piece he calls "Justice," leaving trails in their wake, like rockets in the night. "The Astronomer" includes what seem to be a telescope and a hurtling eye. A giant X of steel stands before "The Other," simultaneously evoking a gun-sight, cancellation and the Stations of the Cross.

These objects -- with their bones and skulls, planetary orbs and glowing spaces -- suggest not only humankind but something vastly greater. The violence that infects this art is held in check by cosmic calm. Beyond the stench of death, the universe rolls on.

Also on display in "Toward the Baroque" is a group of modest photographs by Hope Sandrow of Manhattan. Some 19th-century photographers, the Pictorialists, for instance, used tricks to pull their images toward the realm of painting. Sandrow reveals a similar intention. She moves her camera about so that her images are blurred, and often oddly lit, and sometimes show the ceiling. Their blend of darks and sudden lights, and their ceaseless swirlings -- and the black, old-fashioned frames into which they have been pasted -- do evoke a baroque spirit. Her pictures have some interest, but beside the Stellas and the Morrises they do not stand a chance.

"Directions 1986" includes one installation -- by artist James Turrell -- that is hardly there at all. Turrell offers us a vast black room lit by nothing except three remarkably dim lights. The viewer, upon entering, is certain to suspect that there is nothing there to see -- except the colored flares that glow behind one's eyelids when one goes from brightness into dark. Five or 15 minutes later, if the viewer perseveres, a small reward awaits him. A fuzzy, glowing cylinder of greenish-silver light appears to float in space until -- one's eyes adjusted now -- one discovers there is nothing there but light on the rear wall.

Turrell frequently has been compared with Washington's Rockne Krebs. Both of them make works of art of light. But Krebs' art often awes. This Turrell does not. Its slowness is appealing, but the piece is little more than a small investigation of the limits of perception.

"Directions 1986" is a disturbing exhibition. Our times are not at fault -- look at Morris and at Stella. One can only wonder at the curatorial wobbling that led the Hirshhorn to consider this inexplicable display. It runs through March.