You could fill a room in the Vatican Library with all the books about Pius XII. Few popes have suffered as many posthumous reversals in reputation or had their names invoked as often by critics of the church. Unlucky enough to head the Vatican during the reigns of Mussolini and Hitler; praised effusively by world leaders at his death in 1958; blisteringly condemned in Rolf Hochhuth's 1963 play, "The Deputy," for his apparent indifference to the murder of the Jews; and puzzlingly nominated for beatification one year later, Pius XII today serves mainly as a battleground in the continuing war between conservative and liberal Roman Catholics and Jews.

Time, rather than healing the wound, only aggravates it. In a 1998 statement on the Holocaust, the Vatican hailed Pius XII for saving Jewish lives. In 1999, the British journalist John Cornwell replied in an attack that set off the latest slew of books on the subject. Cornwell's "Hitler's Pope: The Secret History of Pius XII" was criticized for minor errors and its sensationalist title, but appears to have derailed the canonization process. Within the past year, two American historians, Susan Zuccotti and Michael Phayer, published books that qualify but don't contradict Cornwell's conclusions, and two American Catholic writers, James Carroll and Garry Wills, took the controversy as the starting point for books that upbraided the church for its history of anti-Judaism and intellectual dishonesty; both books became best sellers. The most recent defense of Pius XII comes, oddly enough, from a rabbi. In a review in the conservative magazine The Weekly Standard, David G. Dalin, who is also a historian, maintains that the church's record of rescuing Jews in wartime has been grossly underestimated.

The bickering over Pius XII threatens the détente between Catholics and Jews.

The brief against Pius XII goes as follows: He had a soft spot for Hitler and therefore maintained diplomatic relations with the Nazis throughout the war. He failed to protest their atrocities, even when Roman Jews were rounded up, in the now notorious phrase, under his windows. Contrast this, his detractors say, with his treatment of Communists, whom he hated, denounced and excommunicated. His defenders reply that Pius XII spoke up, albeit in generalities, and refused to be more specific for fear of reprisals against the very people he was trying to protect.

Cornwell says Pius XII was authoritarian and anti-Semitic. Church officials say that a genuinely pious man is being slandered. That we keep going around in circles about this probably testifies to the steepness of the challenge he poses to the moral and historical imagination. Neither a monster nor a victim, he occasions category confusion. By what standard are we allowed to judge a man for what he failed to do rather that for what he did? How do we feel our way into the horrifying choices that boxed him in without ourselves succumbing either to easy sympathy or to the false certitude of hindsight? Raul Hilberg, among the greatest of Holocaust historians, warns against rushing to dismiss the pope in his book "Perpetrators, Victims, Bystanders: The Jewish Catastrophe 1933-1945." Pius XII has been accused of being "the supreme bystander," Hilberg says, but should instead be seen as exemplifying the predicament confronted by everyone caught up indirectly in the Holocaust, beset by danger and confusion, limited by faulty perceptions and "delineated by ... nationality and temperament, much as all the inhabitants of Europe."

On the other hand, it's hard to see a pope as merely one European among many. One of his titles is "Vicar of Christ"; in Pius's day, if slightly less so in ours, Catholics were taught to view him as their direct link to God. Pius XII was particularly insistent on that role, using every tool available to enhance his own authority and that of the papacy. In 1933, when Hitler came to power and Pius XII was still Eugenio Pacelli, the Vatican's secretary of state, he signed a concordat with Hitler that legitimized him in the world community and stymied many would-be German Catholic resisters. According to Cornwell, Pacelli was motivated at least partly by a desire to secure the Vatican's control over the large and often independent German Catholic Church.

Hilberg reminds us that by World War II, Christian churches, "once a powerful presence on the European continent, had reached the nadir of their influence." As the world moved away from traditional forms of belief and plunged into ever more terrifying manifestations of political modernism, Pacelli saw his task as that of strengthening and preserving the Catholic Church. He wanted to make sure there would still be a church after the likely destruction of civilization. This helps explain why, for example, he placed the Vatican's political neutrality above its role as the world's leading moral spokesman.

Of the writers who have tried in the past 40 years to tease out Pius XII's state of mind during World War II, it is Hannah Arendt, writing in 1964, whose mix of rigor and compassion yields the most satisfying view of his character. Unlike Hochhuth's Pius XII, a cruel and selfish man, hers is a pope buried in papers and prayers, a cautious bureaucrat shockingly out of touch. His faith in diplomacy was misplaced, to say the least, because Hitler played diplomats like marionettes, but what appears to us as moral obtuseness was actually, she wrote, "the rigid adherence to a normality that no longer existed, in view of the collapse of the whole moral and spiritual structure of Europe." The Vatican also misconstrued the mass killings - not just of Jews and Gypsies but also of Poles and Serbs and their priests, which the pope knew about and never objected to either - as "part and parcel of war," not the senseless murders that they were. It was a terrible mistake, but one that continues to be made by diplomats today.

If Arendt is right (and she may have been too charitable), then Pius XII was at best heartbreakingly wrong. In any event, he can't be used as a weapon against Catholicism per se. If you want to view Pius XII as a saint, you can't ignore his misbegotten silence and damning legacy of his concordat. If he symbolizes anything, it would seem to be a truth more sociological than religious, though one that all religions should probably heed. It is that the logic of institutional self-preservation may be incompatible with moral clarity.

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