In the past 30 years, the Vatican has moved strongly to reassert the authority of a traditional, even orthodox Roman Catholicism – to bring the notion of a "one true church" to Europe and then the larger world. The intent was to reverse the "open" or liberalizing trend of the church represented by Vatican II.

In the past three decades, the Vatican has cracked down on liberation theology, affirmed traditional sexual morality, and is now quietly supporting ultradevout Catholic groups such as Opus Dei and the Legions of Christ – while curbing ecumenical outreach and describing Protestant churches as not authentic.

The most constant, diligent, and serious champion of these moves is a shy but brilliant German theologian, Josef Ratzinger – now Pope Benedict XVI.

Princeton University Renaissance scholar Anthony Grafton, not a Catholic, says Pope Benedict is "probably the greatest scholar to rule the church since [Pope] Innocent III," in the 13th century.

IN PICTURES: Pope Benedict

"There is no great issue, no direction in Catholic theology, not dominated by Ratzinger over the past three decades," says Hermann Häring, a liberal Jesuit theologian who studied with Ratzinger and has written a book about his theology.

Yet a grand effort to restore authority and make the church purer coincides with an epic impurity – abuse of children by thousands of priests and many bishops in the United States, Europe, and elsewhere. To understand Pope Benedict's past, present, and perhaps future responses to the sexual abuse crisis, one must examine the arc of his religious life.

His vision for reforming the Catholic Church was often so all-absorbing that pedophilia got swept under the Vatican carpet, sources say. At the same time, a crackdown on Vatican II – the controversial three-year papal council in the mid-1960s – amplified a culture of fear, secrecy, and hierarchy. "Many rules and codes came down, but efforts to talk 'up' were thwarted," says a Jesuit official in Germany with knowledge of the issue.

"[Pope] John Paul II was the face of the church's world mission, while Ratzinger stayed in Rome, working the books, making rules as the pope's enforcer," says Karl Josef Kuschel at the University of Tubingen seminary in Germany. "Ratzinger has been appointing bishops for 30 years. It is now his church. The bishops today were chosen exactly because they agreed with him."

In dozens of interviews with church officials and theologians in Germany, the US, Spain, and France, many Catholics say the Vatican is not missing cues nor "tone deaf" in its handling of pedophilia. Rather, the abuse cases are playing out fitfully within the pope's vision of the church as ultimate arbiter of spiritual authority, Scripture, and holiness on earth. In this sense, the Vatican is not looking to adapt, modernize, or open itself to new interpretations. Recent Vatican statements against women's ordination, and reaffirming priestly celibacy, are small examples.

"The world is evil and the church is pure," says an Austrian church official. "This is serious for Benedict. He doesn't want the church to be a joke. He's suspicious of chaos and avoidance of discipline and order, and of human efforts to adopt popular culture and create church out of the world, instead of a church that transforms the world. This deeply upsets him. He sees all salvation taking place inside the Catholic Church. He believes that."

Yet ironically, child abuse has arguably brought greater disorder than the ferment of Vatican II in the late 1960s. This spring, the pope described pedophilia as "the petty gossip of dominant opinion" before shifting 180 degrees and asking contrition from St. Peter's Basilica on June 11: "We ... insistently beg forgiveness from God and from the persons involved, while promising to do everything possible to ensure that such abuse will never occur again."

From progressive to traditionalist

Ratzinger was not always seen as the conservative enforcer of Catholic doctrine. In 1965, the arrival of Ratzinger to the theology faculty at Tubingen brought a stir of anticipation. Ratzinger's bestselling "Introduction to Christianity" seemed a new impulse for democracy and freedom. The school had a joint Protestant-Catholic faculty. Change was in the air. Ratzinger was brought in by Hans Kung, a progressive young Swiss lion of Vatican II; for a time, it looked as if the two men were at the start of a beautiful friendship.

Nazism and the war had disturbed young German Catholics who were suspicious of absolute ideology. Vatican II appeared to "open" the church and allow dialogue and airing of views without fear of ecclesiastical reprisal. At Tubingen, Protestants partook of Catholic learning; Catholics learned Protestant concepts of scriptural interpretation and subjective ideas about spirituality from the teachings of Swiss theologian Karl Barth and German theologian Rudolph Bultmann.

Yet Ratzinger's first lecture to the joint faculty, an important tradition for new professors, was surprising. He spoke on "The significance of the church fathers for Christianity." Mr. Kung was "a little shocked," says Professor Häring. "Rat­zinger was saying the basis of true theology was not the Bible, but the Bible as interpreted by five centuries of church fathers. He was basically telling the Protestant faculty, 'Get lost.' He was saying you must return to Greek theology ... to Hellenism."

The student protest marches at Tubin­gen in the '60s were a watershed for Rat­zinger, moving him toward conservatism. He departed to a quiet Bavarian college. He wrote against democracy in the church, berated the influence of Marxism, and criticized what he called "the dictatorship of relativism." He disliked the language of individualism, of crisis of faith, the search for freedom and meaning, and existential moments. "He saw it as individuals separated from the collective institution of church, where salvation and meaning are found. In service to the true church, one found a new life," says Professor Kuschel.

In 1977, Ratzinger became archbishop of Munich and Freising. Former Jesuit Paul Imhoff remembers Ratzinger as absorbed in medieval Catholicism. Mr. Imhoff, who was ordained by Ratzinger before leaving the church to marry a theology student, went to a "professors' carnival" with him. "We had jokes, dancing, harmless fun ... Ratzinger was charming. But the whole time he spoke about restoring the old Europe ... where the church takes precedence over the state."

Pedophilia not on his radar

Pedophilia cases started mounting in Vatican files in the 1980s. But now, as head of church discipline, Ratzinger was primarily focused on silencing priests or liberation theologians, such as the Brazilian Leo­nardo Boff, who tried to empower farm­ers and peasants. The 1990s brought strictures against abortion, gay rights, same-sex marriage, contraception, and promotion of abstinence and celibacy – just as US bishops were reporting hundreds of child abuse cases, but getting little clarity on how to handle them.

Most heads of the church's Congrega­tion for the Doctrine of the Faith (CDF) serve two terms, or 10 years. Ratzinger served 24, then became pope.

In recent years, a Vatican focus on ecumenical outreach has given way to evangelical outreach. In June, a new pontifical office to "evangelize" areas of the world that have suffered "an eclipse of the sense of God" was announced. The church has rebuffed Protestants and drawn sharp lines on Islam. But Rome has improved ties to Eastern Orthodox churches.

On July 21, Russian Orthodox Patriarch Kirill praised the pope for holding firm against women priests and not succumbing to "sinful elements of the world" that have entered Protestant churches via gays and female clergy, and offered to work with the pope on world issues.

Today, after his 30-year quest to reshape the church, the sex scandal may be a sizable legacy. It is unclear where the pope is headed. In the past month, there's been some shift in tone and attention. In late July the church extended to 20 years the period that victims' claims can be investigated. But the key question of whether offending priests should be reported to civil authorities is undecided in Rome.

Beyond his few pronouncements, the pope's views on the sex scandal are an enigma. Vatican sources say the pontiff spends time writing books and only sees two church officials regularly. "Even bishops now wait two weeks or more for a meeting," says a church official who is concerned about the pope's isolation.

IN PICTURES: Pope Benedict