CAN A WORK OF ART express that which is inexpressible? And if an artist attempts the ineffable, will he not do so at great risk? This was the notion Balzac proposed in an early, little read story, The Unknown Masterpiece. The hero of this tale, Frenhofer, is one of Balzac's archetypal artist, a man who has worked for years on a painting he has concealed from friends and admirers. Since Balzac sets the story in 1612 he has his artist invite Francois Porbus, a painter in the court of Henri IV, and Nicolas Poussin to see the finished canvas. When the picture is unveiled, what they see is "colours piled upon one another in confusion and held in restraint by a multitude of curious lines which form a wall of painting." Poussin is dumbfounded, Porbus mystified; both are thrown out of the studio by a enraged Frenhofer who, that night, burns his painting and then dies.

"Who," asks the art critic Dore Ashton, "was Frenhofer?" -- thus propelling a ruminative essay into a kind of art-critical detective story. It is only the first of a series of questions Ashton raises. Her "fable" becomes only partly Balzac's because as Balzac himself says, "It is the property of a good fable that the Author himself does not know all the riches it contains." Indeed, as the fable of Frenhofer gathers patina, it takes us further and further into the unknown, even into the "abyss" at which Baudelair stared -- infinity, the nothingness, endless space, perhaps madness.

Frenhofer became an obsession for Cezanne and Picasso. Cezanne identified himself with Frenhofer and trembled. "But there is no perfect circumstance, the absolute ideal is a betise." As Ashton sees it, in Cezanne's case "Frenhofer's tragic error always stood before him, and he never reached his dearest hope -- the hope of certainty." After Picasso illustrated The Unkonwn Masterpiece, Frenhofer remained ensconced in Picasso's imagination. "There is no abstract art," Picasso declared in 1935. "You must always start with something. There's no danger then, anyway, because the idea of the object will have left an indelible mark." (Yet in Picasso's "Vollard Suite" etchings, the central image all but disappears in a mesh of wild, gyrating lines.)

The image of Frenhofer would fuel the uneasiness of the poet Rainer Maria Rilke and the composer Arnold Schoenberg. Rilke's angels, Schoenberg's fascination with Emanuel Swedenborg and other mystics were a further search to express the inexpressible. Like C'ezanne and Rilke's master Rodin, Rilke needed "the union, the law, the root, the cell from which to craft his vision." Even so, at the end of his life he confessed: "The terrible thing about art is that the further you go into it the more you are pledged to attempt the uttermost, the almost impossible." In the end it was reason that saved Schoenberg (silence between 1913 and 1923). The marvelous invention of the twelve-tone row created one musical masterpiece after another.

It would be hard to say whether Dore Ashton's own fable ends with her discussion of the discoveries and triumphs of Kandinsky and Mondrian, or the rise of a powerful school of Abstract Expression in the years following World War II. She is too wise not to realize that a good fabric never knows "all the riches it contains." It is her gift to throw us back again into looking, hearing, reading all that is best not only in our own time, but in those periods of the previous century which inform much of life with the desire to experience, to discover what we don't know.