Once upon a time, as the Transylvanian folk tale goes, there was a Poppa Frog, a Mamma Frog and a Baby Frog. When the baby grew into boyhood, his mother warned him to keep quiet--and not to croak--thus escaping the attention of the snakes and wild animals. One day the boy frog hopped happily to a pond and croaked to his heart's content--that is, until a mountain goat sprang from behind and ate him up. While his mother grieved angrily, his father told her not to scold her dead son. Said Poppa Frog: "He had the courage to be himself."

"The Frog Who Dared to Croak," a thought-provoking fictionalized memoir of a famous Marxist philosopher and literary critic, rings a half-dozen variations on this allegory. Richard Sennett is the acclaimed author of such works on social psychology as "Authority" and "The Fall of Public Man: On the Social Psychology of Capitalism." This novel, for all its academic hand-wringing and soul-searching, could have, in fact, been called "The Fall of Private Man: On the Social Psychology of Communism."

The prototype of its hero is obviously Hungarian philosopher Georg Lukacs (1885-1971). Lukacs, like Sennett's Tibor von Grau, was the son of a banker who found early fame as a writer, became an official in the 1919 Bela Kun Communist regime in Hungary, went into exile in Vienna, later lived in the Soviet Union, returned to Budapest after World War II, and retired from political activity after the anti-Soviet Hungarian revolt in 1956.

Sennett uses this general outline, presenting the life of Tibor von Grau through scraps of autobiography--letters, clippings, journal entries--hidden from the secret police and dusted with flour and sugar from their surreptitious stopover in two kitchen canisters. (The paranoid, or practical, Grau leaves a pornographic novel--"heterosexual and sadistic, the safest genre"--lying about so that the "workmen" who had "come about a gas leak" could find something.) The autobiographical notes have somehow managed to survive and are published with minimal comment by a London editor.

The turn of the century finds the young Grau enjoying the rich, discreet charm of the bourgeoisie. He is a brilliant, appallingly arrogant child--a homosexual bully. At 8, his less fortunate classmates are called "loathsome." They "had pimples, but they resisted me. I had to have them, to conquer them." Later, he is drawn to Budapest Municipal Park where poor men sleep in trees (ropes are tied across limbs producing a makeshift hammock), and poor boys from the countryside have sex for money--and comfort. After a while Grau sees these men as his working-class lovers and refuses to pay for sex again, wanting instead True Love--the romance of comradeship.

Grau's transformation from capitalist to socialist is amusing but credible, and these encounters, which are symbolically punctuated by the croaking of frogs in the park, have a certain humanizing effect on him. Committed to the ideals of Marxism, the young critic becomes the Deputy Director of Cultural Propaganda and quickly revises the famous frog fable for the masses. (A colony of frogs will be swallowed alive if they croak as individuals, but if they croak together they will scare off the deadly snakes.) He soon finds that too many Marxist ideals are being turned topsy-turvy by a new bureaucratic system that turns victim into criminal, poem into polemic, sage into stooge.

"A face without a mask gets frostbitten from the cold," writes a fearful Grau. His life caught in too many contradictions, Grau begins to cover up and eventually becomes a master of masquerade. This is never more wittily dramatized than when he escapes into exile in drag, made-up by an actress friend and dressed in a peasant skirt, babushka and clogs. Outside, a soldier whistles at him, and the frightened professor allows himself a twinge of pleasure, perhaps the same preening, distancing ambivalence Tennessee Williams' heroines are often experiencing, blowing kisses from a tacky float.

Only here does Grau come close to being a full-blooded individual or a fully developed character. Mostly he is a straw man--a Babbitt at war with himself--whom Sennett hangs society's ills upon so the author can cover herculean sociological ground. Is this why Sennett's hero is born into the bourgeoisie and is both a Jew and a secret homosexual?

At this midway point, despite moments of intellectual precision and black humor, the book becomes a jumble of redundancies. Grau's mask hardens as he uses marriage as a coverup. Later, he is assigned to the Minsk Academy of Literature where he becomes a party hack and plays verbal leapfrog with Stalin. The frog motif jumps out of these pages quite frequently, most memorably in a tale Grau entertains German prisoners of war with (in this ditty a master race of frogs is defeated because they lacked basic fraternity) and in a long story set in a Transylvanian mountain artist colony that fails because these "troubled dreamers" could not "remove themselves from the vices and sordidness of the world below."

The didactic organization and texture of the novel is fascinating and sometimes, in its second half, wearisome. But Sennett's meditation on the divergence between the public and private self, the compromises made to survive, and the breakdown of the spirit when the two selves fail to reconcile, is a provocative display of literary scholarship. The question addressed in the final section, which dramatizes the behind-the-scenes political upheaval during the anti-Soviet revolt in 1956 Hungary, is whether or not Grau will finally croak, and thus, speaking his mind, take his life out of his own hands. Sennett's careful denouement is a satisfactory answer for the professor with the poignant frog caught in his throat.