IN JANUARY 1984, the democratically elected and newly inaugurated president of Argentina, Raul Alfonsin, called the country's most distinguished man of letters, Ernesto Sabato, and asked him to join a Commission on the Disappeared, whose task was to review the six-year reign of terror of the junta that had ended the year before.

Sabato, whose novels have won him international acclaim, unhestitatingly accepted -- although, as he told Alfonsin, he knew "we were going to suffer a lot, not just because of that descent into hell, but also because the repressors are still free and armed."

The commission was made up of a Catholic bishop, a Protestant bishop, an American rabbi, members of the Human Rights Commission, a lawyer, a philosopher, the former rector of the University of Buenos Aires, a journalist, a scientist, a heart surgeon and two former members of Argentina's Supreme Court.

Sabato was chosen not just for his fame. He was one of the few who had dared to speak out against the junta, to denounce the torture, repression and disappearances that it had justified as necessary to save the nation for the West and Christianity. He made a point of never saying in the foreign press what he did not also say in Argentina. Presumably his prestige saved him from the fate suffered by at least 9,000 "disappeared" Argentines.

Sabato was elected commission president, thus insuring a report of exceptional literary quality. He wrote the majestic, heartbreaking prologue, which concludes:

"Great calamities are always instructive. Doubtlessly the most terrible drama the nation has suffered in its history that lasted the duration of the military dictatorship . . . will help us understand that only democracy can preserve people from such horror, that only democracy can maintain and save the sacred and essential rights of the human being. Only in this way can we be sure that . . . these events that have made us tragically famous in the civilized world will not be repeated."

"Nunca Mas" (Never Again), as the commission's report is entitled, has sold 300,000 copies in Argentina. It is meticulous and eloquent, the facts presented drawn from nine months and more than 50,000 pages of testimony. Its findings were turned over to the judiciary and nine members of the junta have been tried and found guilty. Two top military commanders, former president Jorge Videla and Emilio Massera, were given life terms -- ironically, Argentina has no death sentence. Hundreds of others are being prosecuted.

Sabato, now 75, came to Washington recently to participate in symposia on his literary work. He is a somber, elegant man. He talks with pain about his uncommon civic duty, but with pride. He hopes that the process instituted by the commission will serve as a model for other nations that repent of their official savagery and seek to make amends through justice.

He was not suprised by the hideous evidence presented to the commission. He has a tragic view of life, as reflected in his novels, and believes that the struggle against the evil in human nature is unending. Argentina is not alone in its record of sadism and cruelty -- it is enough to mention the Germans, the French in Algeria.

Every morning when he woke up during his sickening toil, Sabato would say to his wife, "Now the nightmare begins.

"There is no precedent anywhere in the world for some of the methods used," he says. "We have been given evidence that children and old people were tortured so that their relatives would give the information which their captors sought."

The commissioners visited many of the 300 torture centers where Argentines, some of whom had done nothing more than have their names found in the address books of dissidents, were held, tortured and sometimes killed.

The commission's first secretary had to be relieved of duty, finding the stories of "one atrocity worse than another."

"And although we must allow justice to have the last word," Sabato wrote, "we cannot be silent about the things we have heard, read and recorded; they go far beyond the merely criminal, coming into the black category of crimes against humanity."

Not all Argentines approve the report. The Mothers of the Plaza of May -- those valiant women who paraded around the government square every Thursday, wearing white kerchiefs and holding aloft pictures of their "disappeared" loved ones -- have protested vehemently that more criminals have not been rounded up and tried.

"We understand the pain and sorrow of the mothers, but the mothers must understand that justice works in this way," said Sabato. "It is slow. The only quick justice belongs to totalitarian and despotic countries."