Come back, Minimalism, all is forgiven!

Ad Reinhardt (1913-1967) painted blackness. Dan Flavin (1933- ) is a poet of white light. Both are now exhibiting at the Corcoran Gallery of Art.

Because they stand against the messy with implacable integrity, Reinhardt's blacks and Flavin's whites shame the excesses of contemporary painting. Just flip through the art magazines. Barking dogs, scrawny sketches and figures believed mythic lurch about like sloppy drunks in much of 1984's art.

Reinhardt's show, and Flavin's, together make one yearn for Minimalism's return.

Reinhardt's "Black Painting" (1962) is a black monk of a picture. It looms out of the wall. The black cross it presents is done in blacks so subtle one can look and look again and not be sure it's there.

Flavin's "monuments to V. Tatlin" chastely glow. (Flavin prefers the lowercase "m".) They are made of nothing special -- of bland fluorescent tubes and the bland enameled mounts one finds at hardware stores -- but they are touched by grace. There are 39 on view. They preside over the atrium, and over three of the museum's grandest sky-lit halls. They illuminate the air itself.

The 17 Reinhardts on display are all from the collection of Gilbert and Ann Kinney of Washington. These abstract pictures trace the path the painter took as he struggled to discard busy colors, complex shapes, the accidents of staining, and other elements of painting he came to see were nonessential. In rising toward the monochrome, in emptying his pictures -- and in emptying them of doubt -- he made his art grow stronger.

Reinhardt's "Black Pictures" aren't pictures of crosses or right angles or squares. He insisted, notes Jane Livingston, "on the primacy of the uninterpreted, noneditorialized, uncontextualized, nonsignifying, object in itself."

The great irony of Minimalism is that black or nearly all-black pictures by Kasimir Malevich, Frank Stella, Barnett Newman, John McLaughlin, Robert Rauschenberg, Mark Rothko or Ad Reinhardt, although nearly "empty," feel -- when they are lived with -- as if they were full.

The "living with" is crucial. These paintings open slowly; they reveal themselves with time. Marcel Duchamp said, correctly, that the painter makes only half the picture; the viewer does the rest. The Kinneys' five-foot-square black Reinhardt with its flickering of light-in-dark -- like a mantra or a mirror or view over the sea -- is able to call up the all, the look of life itself.

Reinhardt's show is little. Flavin's show is big, ambitious, grand. But in Flavin's objects, too, one feels the presence of a the seeker, the purist, the obsessive. He's been making these "monuments to V. Tatlin" since 1964, and is at it still.

The grids of Piet Mondrian, Mies van der Rohe, Agnes Martin, Sol LeWitt, have a beauty that is founded on the subtlest adjustments of position and proportion. The same holds for Flavin's beautiful, no-nonsense constructions of fluorescent light. Each has been installed in precisely the right place.

Flavin's first "monument" consisted of seven butted fixtures with the longest in the middle and the shortest at the sides. He used 2-, 4-, 6- and 8-foot bulbs so that that the simple, strict, steeple-like construction read 2,4,6,8,6,4,2. "monument" number two is a sort of a reversal: two eight-foot tubes stand at the ends; there is a two-foot white tube at the middle. Tatlin, the obsessive, revolutionary Russian Constructivist, would have liked them, I think.

He was a former sailor, an engineer, a dreamer (who dreamed, like Daedalus and Leonardo, of providing man with wings for muscle-powered flight). He loved -- as does Dan Flavin -- the clean and the iconic. Aleksandr Rodchenko visited Tatlin's studio in 1911. "He lived there by himself and, as befits a sailor, everything was clean and in order . . . The number of variants of the same detail was astounding . . . Everything was studied carefully and with great taste . . . He liked everthing simple, solidly made and vigorous." So does Flavin. Tatlin thought modern materials, like steel and glass, "comparable in their severity with the marble of antiquity."

Something about Flavin's art feels peculiarly religious. His "monuments" on view are as simply right as white clapboard steeples, or hymns hammered out four-square. Their classical simplicities, their uncompromising certainties, the even ghostly glow of their gray-white light and the way their glowings seize the wall make the viewer think of grace.

Flavin's art, like Reinhardt's, demands that we confront the perfection and transparency contained in the immaculate. At a time when slop-art and gut-spilling self-indulgence are still so much in fashion, it is astonishing how much the Minimalism at the Corcoran manages to refresh.

If abstract art is to survive, Minimalism -- in some as yet undreamed of form -- is certain to return. That these shows make certain. Tasting Reinhardt's blackness and Flavin's fierce white light is like tasting pure clean water after supping for too long on sawdust and syrup. The Reinhardts will remain on view through Nov. 16, Flavin's "monuments" through Nov. 25.