When my eyes first took in the loveliness, the order and the beauty of the campus Thomas Jefferson laid out for the University of Virginia at Charlottesville -- the Rotunda and the Lawn stretching before it, the utter rationality of the Jeffersonian plan, the perfection of its form -- I felt as if I had begun to understand for the first time the Age of Reason, and what a magnificent, noble and stirring effort it was against the frightening darkness and the real terrors lurking out there in the wilderness -- not only a metaphor at the time the university was planned, but a present reality just the other side of the visible mountains and almost continent deep. I also felt that any one person's time there ought to be limited, lest he or she be seduced into believing this classical calm was a reflection of the world instead of something the mind of man in a finer moment had imposed upon it.

This campus and that Age of Reason came to mind yesterday when I read about the tiny band of pilgrims that arrived for the second time Sunday morning at the railroad ramp at Auschwitz. The first time they had come as children in cattle cars, and because they were twins they were spared the fate of their mothers and the other children who were led to the gas chambers upon arrival. This time they came in a light snow to commemorate the 40th anniversary of the liberation of Auschwitz by Soviet troops.

Auschwitz was a place of unimaginable horror -- or so we would like to think; the horror was in fact not only imagined but realized. Between 3 and 4 million people, the vast majority of them Jews, were systematically, efficiently murdered and rendered into ashes at that small cluster of camps from July 1940, when the first prisoners arrived, until it was evacuated 41/2 years later. Between three and four million men and women and children, waving goodbye to one another and exterminated like vermin because they were Jews or otherwise thought undesirable in the Nazi master plan: homosexuals, some Christians of tender conscience, and others who could neither avert their eyes nor get along by going along.

There have, of course, been other ghastly genocidal crimes in the history of the human race, in the history of this century -- the slaughter in Cambodia under the Pol Pot regime, in Uganda under Idi Amin, the Armenians in Turkey, in the Soviet Union under Stalin -- in, lest we forget, the history of this country, once inhabited by tribal Indians, built in part -- the part that was the original university in Charlottesville, for example -- by the labor of slaves. But Auschwitz -- and the whole Nazi horror -- wa different, not because of its scale alone but because of its extreme rationality, because a whole school of thought grew up to explain and justify it in the name, often, of science and the improvement of man. Auschwitz, too, was a temple of reason -- reason perverted, of course -- and Dr. Josef Mengele, who, if he is alive as many believe, turned 73 on Sunday, was its high priest.

It was Dr. Mengele who culled the twins -- and dwarves and cripples -- from the arriving hordes for genetic experiments that, it was hoped, would produce a superior race free of ordinary human defects and, incidentally, change the color of their eyes. Of the 1,500 pairs of twins involved in these experiments, fewer than 180 individuals survived. When Dr. Mengele was through with the children, he injected their hearts with phenol to preserve them for dissection. He also selected those arrivals -- mostly women and the other children -- who went immediately to the gas chambers and then the crematoriums, and those who would work for a time. It was all very scientific and, considering the size of the operation, very efficient, like the layout of Auschwitz itself. It is altogether possible that Dr. Mengele and his associates even considered their work humanitarian; they were, after all, building for the future. Yes, there was an order to Auschwitz, and an elaborate rationale behind it. It was all so reasonable, once the premises were accepted. As reasonable as Jefferson's Rotunda and Lawn and that whole Age of Reason of which it was the ultimate grotesque perversion.

It has always seemed to me that the most appropriate monument to the Holocaust would be a place of Euclidean proportion and austerely classical beauty, with the music of Brahms, perhaps, playing in the distance. Adam Kowalski, a survivor who came back to Auschwitz on Sunday asked, "Where is the logic?" I would carve on the entablature: "The logic is here." That is what we must remember, that the logic s there. That, and the horror.