THE TRIAL in Buenos Aires is producing compelling testimony of systematic torture and brutality under the junta that recently ruled Argentina. The present democratic government is prosecuting nine of the junta's most prominent figures, including three former presidents of the country. But the purpose of this trial goes beyond the questions of individual guilt and innocence. It is establishing, in great and indelible detail, what actually happened in an especially dark and violent period of the country's history.

There is an important parallel here to the service performed by the Allied governments' trials of the Nazi war criminals after World War II. The Nazis' offenses were of an altogether different order of magnitude from those of the Argentine generals and admirals. But in one case as in the other, the process of assessing guilt serves the indispensable purpose of establishing a historical record. In Buenos Aires as in Nuremberg, the record is being laid out under the rigorous conditions of the courtroom, with sworn testimony by identified witnesses, subject to challenges by the defendants.

The Nuremberg trials foreclosed the success of attempts by demagogues and neo-Nazis to claim that the accounts of genocide and the death camps were merely lies and calumny invented by their political enemies. Similarly, the trial in Buenos Aires is not only enforcement of the law but an essential step to prevent the junta's supporters from arguing, in the future, that the accounts of recent experiences are mere fabrications and unproved accusations. The accusations are being proved with a wealth of description that makes the skin crawl.

One policeman gave testimony regarding several murders, in the hope, he said, that his children would not have to live through a repetition of that savagery. That's a good reason. Government rests on a foundation of national tradition, and good government requires a clear and unsentimental understanding of the past.

The Nuremberg trials have occasionally been described as an act of vengeance inflicted on the defeated by the victors. That's wrong. The Nuremberg record -- vastly amplified by the work of a generation of German historians -- has been a crucial contribution to the integrity of postwar politics. Similarly, the Buenos Aires trial is establishing certain truths that will enable the country to pass judgment not only on the nine defendants but on their whole style of rule and its consequences. In that sense it is a political trial, and strengthens the prospect for democracy in Argentina.