The 50 tribal objects from Katherine White's collection, now on exhibit at the National Museum of African Art, are among the best she bought. That is the consensus. The Smithsonian Institution says they are "masterpieces" all, and it is true that they are beautiful, visually charged.

They are so beautiful, in fact, that their beauty makes one wonder: Is it grounded in the work itself, or does that beauty exist mostly in the westernized museum-trained eye of the beholder? And whose beauty is it, anyway? Is it theirs or is it ours?

Our museums look like temples and our van Goghs sell for millions because our society agrees that something semisacred imbues masterworks of art. Tribal masks were sacred, too.

Does a mask no longer used in dances, or a desecrated altar, become a "masterpiece" of art just because it is good looking? Should a sacred tribal object ever be required to give pleasure or delight to an unbeliever's eye? Do a late van Gogh self-portrait, drenched in Vincent's martyrdom, and an ivri from Nigeria, soaked in dried dog's blood, partake of the same blessedness? Or do their sanctities collide?

These questions have of late been given special force by a spate of serious tribal exhibitions, by the "Primitivism" show at New York's Museum of Modern Art and by the African museum now abuilding on the Mall. Everyone with eyes would be likely to acknowledge that the tribal objects at the Modern are terrifically good looking. The museum's William Rubin insists that he picked them for their presence, for their power, and that he paid no attention to their iconography, their functions and their gods.

Does an African museum have another duty? Is seeking beauty its main mission?

There is a Kongo nkondi from Zaire in the present exhibition. He is a muscular standing figure -- whose chest and shoulders, back and neck, bristle with a thousand bent and rusted nails. How are they to be read?

Are they signs of pain and suffering, as are the nails piercing the hands and feet of Christ? Perhaps they signify the fibers of a harmless bristly cloak? Collector Katherine Coryton White (who began buying African art in 1960, and died in 1980, leaving 2,000 pieces to the Seattle Art Museum) liked to write about her objects in poetic prose. She found those rusted nails scary. They made her think of the pain-delivering pins stuck into voodoo dolls in Hollywood's B-movies.

Danger gathers . . . iron made to penetrate by violence . . . hair, beads, gum, bone, the crust of dusty air. It's like a poisonous mane, festering . . . Lethal. Each addition is an episode of pain and revenge which hangs with accumulated malice . . .

White got it wrong. Her nail fetish, like those in the Modern's show, is not a hapless victim of heh-heh malice. He is a magistrate, not a martyr. He is an authority figure, a kind of judge. His mane of rusted nails -- like the law books on the bookshelves behind the politicians -- signifies a set of considered judgments. Each nail stuck into his body commemorates an oath, a path of action chosen, a dispute resolved. The gavel of the auctioneer is used to seal sales; the judge might pound his bench to emphasize a ruling. Each nkondi nail delivers a similar message: There! Now it is done.

Another splendid object in the White collection -- a Mossi karan-wemba mask from Upper Volta -- has a beauty that to western eyes is easier to see. A woman, a beautiful woman, naked, carved of wood, stands upon the wooden mask. A pierced plank tall as she is grows out of her head. That pierced plank has been called (by a Mossi who should know) "the road of the dance with the dead." Perhaps that plank allows her to communicate with her ancestors; perhaps it is a sign of her holiness, her grace. But even if it were not there she might be called a "masterpiece." For her beauty, her museum beauty, is wholly beyond doubt.

Just look at her shoulders, her posture, her long neck, her fine back. Her beauty is familiar. The beauty of the female nude -- a beauty shared by the Venuses of Greece and Rome and those of Hollywood as well, a beauty reinforced in every western art museum -- is glimpsed again and clearly in this work of art.

Katherine White's nailed nkondi may also be a "masterpiece," but that recognition demands another -- and much rarer -- kind of connoisseurship. Suppose it were displayed beside 60 other similar figures from Nigeria. Would it stand out as special, or would it become just one of the guys? One imagines that its power, its authority -- its beauty -- derived, at least in part, from the prayers recited to it, or sacrifices offered, or from the sacred grove in which it once lived. But White's nkondi is now encased in a museum, an authority no longer. Has its beauty soared or has it drained away as sanctity dissolved?

There are many other objects in the Katherine White exhibit that raise old and knotty questions of esthetics. Suppose a mask was made to frighten, like one worn for Halloween: Could such an object be a masterpiece if it was created only to go "Boo"? Or is some denser, higher seriousness required?

One mask in the White show, a Yoruba Epa, weighs some 60 pounds, and for good reason. Such masks are used in tests. The catalogue tells us that the Oloko dancer who wears it is expected to leap, in a single bound, onto the top of a five-foot mound while wearing such heavy objects. "If successful, he brings an assurance of good luck to the farming and hunting for the year. If not, sacrifices must expiate his failure." He had better not stumble. A much lighter Epa, carved with more finesse, might please a western eye. But could it be a masterpiece? Light Epas aren't the real thing. They do not really count.

Little was widely known about the carvings of black Africa when Picasso first "discovered" them in the Museum of Man, in Paris, in the spring of 1907. Perhaps it is still possible for a non-African to pick a tribal "masterpiece" (as Picasso did, as Rubin does, and as White did, too, at least to a degree), while knowing next to nothing of the dances of black Africa. Perhaps all tribal masterworks, and all great works of art from whatever culture, share a certain something -- "I know it when I see it" -- that subtle connoisseurs are able to detect. Perhaps and perhaps not.

The word at the Smithsonian is that the permanent collection of the National Museum of African Art is still sadly short of objects of the highest quality. The National Museum apparently owns fewer "masterpieces" than did White. Should the National Museum strive to get them? Or should it, as its first priority, investigate the context -- the sacred dances, foods, taboos and incantations -- in which they must be judged?

The present exhibition doesn't answer these questions. But it raises them. It has been cleanly, simply installed by Caroline Michels. Too many of its catalogue's photographs, however, are marred by such high-contrast artiness and unnecessary dramatismo that one can hardly see the tribal objects in them. "Praise Poems: The Katherine White Collection" will remain on view at the museum, 318 A St. NE, through Feb. 24.