Keeping and Questioning the Faith : RELIGION : CHRISTIANITY: Essence, History and Future,<i> By Hans Kung (Continuum: $44.50; 936 pp.)</i>

Is it any wonder Hans Kung is at odds with the Vatican? His latest book, “Christianity,” is so weighted with pope-bashing that even anti-papists might wince. Critics who question how the office came about in the first place, or who wish to remodel it now, will find a soul mate. The irony of this is not to be overlooked: Kung is a Roman Catholic priest.

More than one particular church office, an entire religious tradition gets a mighty shake from Kung’s passionate pen. Early in the book, he defends his revisionist position: “What must be pursued is not a historical approach in love with the past but one which is critically related to the present, and in such a way that the present can be understood from the past and the past from the present.”

The book’s subheadings crackle with discord: “The Dark History of Jewish Christianity.” “The Losers in History: Women.” “The Infallibility of the Pope--Originally a Heresy.” “The General Condemnation of Modernity.” “The Repression of Modern Catholic Theology.” Massive research and keen analytical thinking fuel this merciless comeuppance.

To organize his material, he structures a system of paradigm shifts: A paradigm represents an entire constellation of beliefs, values and techniques shared by the members of a community; a shift is the replacement of an existing paradigm by a new one.

The broadest shifts Kung explores are the time-honored variety. He revisits the Christian church in Jerusalem and Rome, explores medieval European developments through the Protestant Reformation and evaluates the effect of science upon religion as seen during the 17th century Enlightenment.

In the modern age, his paradigm turns upon the Second Vatican Council of the mid-1960s and the years that have followed. Here, Kung gives his opinion on issues that are making daily news, among them the debate over women’s ordination (he’s for it), the celibacy of priests (he’s pro-choice) and the performance of Pope John Paul II (he sees this pontiff as a deeply spiritual man but one incapable of appreciating democracy). The pope’s outspoken defense of moral absolutes, as opposed to personal adaptations, has made him a voice for orthodoxy, which is not Kung’s position.

Over each historic shift explored in this book, rich layers of detail are poured. In the church of the first century, Kung explains, women were deacons and leaders of their own house churches. Only later were they banned from leadership roles. In the Middle Ages, mysticism, a form of rapt contemplation practiced by Francis of Assisi and Teresa of Avila, among others, was discouraged by the official church. It was seen as disruptive to community worship. Interestingly, this solo form of prayer has captured the attention of many modern spiritual explorers.

Along with his passion for details, Kung’s ongoing commitment to unity among world religions is most apparent. He is director of the Institute for Ecumenical Research in Tubingen, Germany. In each chapter he looks for compatibility among Christian, Jewish and Muslim beliefs.

“Don’t the three religions of revelation . . . and especially the Hebrew Bible and the Qu’ran, have the same basis?” he asks at one point. “Doesn’t one and the same God speak abundantly clear in both?”

For Muslims and Christians, he sees the potential for a shared understanding of Jesus Christ, although Muslims do not believe that Christ is divine. “Christians and Muslims believe in a single God and therefore a single salvation history: Just as Christians already regard Adam, Noah, Abraham and all the patriarchs of Israel as ‘Christians’ before Christ, so Muslims recognize the same patriarchs . . . and also Jesus as ‘Muslim’ before Muhammad.”

While this open interpretation might well cause both Muslims and Christians to raise objections, Kung’s efforts to find theological rapport, carried through the book, are worth consideration at a time when religious tolerance and world peace have never seemed more vitally interdependent. Clearly, no one is more aware of this than Kung. “Christianity” is the second book in a trilogy. The first, “Judaism,” was published in 1992. He is now completing one on Islam.

Scholarly genius sparkles in this history. Still, all told it proves to be a troubled and fearsome account. A bit of background about the author seems relevant. A Swiss theologian and priest, now in his 60s, Kung was one of the Catholic theologians called to take part in the Second Vatican Council. Hardly more than one decade later, the most liberal interpretations of the V-II documents cooled, and Kung’s criticisms of the church heated up.

In 1979, the Vatican stripped him of his license to teach theology and forbade him to call himself a Catholic theologian, primarily because of his ongoing questioning of the doctrine of papal infallibility. A prolific writer, he continues to be to the left of center on other doctrinal issues as well. For years the Vatican has kept a dossier on him. Still, many see Kung as a reformer, not a radical.

Given Kung’s contentious relationship with the church hierarchy, some criticism in his book seems downright spiteful. In particular, his personal barbs about members of the Vatican undermine his own credibility. This is particularly apparent in his view of the papal office, which seems crafted to support his ax to grind against the doctrine of infallibility.

In the 4th century, he begins, Eastern and Western Christianity accepted the bishop of Rome, later to be given the title of pope, as first among equals. They were in the habit of consulting him on matters of doctrine. Primacy, the doctrine meant to give the Roman pope ultimate power over all of Christianity, was not widely accepted, however.

Eastern Christians considered Rome unique because the great apostles, Peter and Paul, were buried there. And Peter, the first apostle named to rule over the church, did in fact receive his role as head of the early church directly from Jesus. But nothing in Scripture gave the same authority to Peter’s successors, they asserted. Kung takes up the argument.

Most of the world’s more than 1 billion Roman Catholics would argue him to the ground about this. Scripture and tradition both support the papacy, according to church teaching. The office evolved from the two sources.

Despite his complaints, he gives the office credit for its unifying features. It is just that he would reform it. “Should it be a primacy not in the spirit of Roman imperialism but in the spirit of the gospel?” he asks. He recommends greater openness to discussion about differing points of view, along with diminshed authority.

“Loyal dissenters,” as he refers to himself and others who see things his way, will feel fortified by Kung’s vigorously argued position. But, the vast majority of Christians may find themselves left with a very unsettling question: What is the other side of this story?

No answer is included here.

Kung’s apparent fury over what he sees as a history of injustices by the powers that be, does cast a shadow over the book. It would not serve as an objective reference tool. And yet, the encyclopedic array of material is most impressive.

The book includes bits of history on the sacraments:

* Infant baptism began during the reign of Emperor Constantine, in the 4th century. Earlier, it was only for adults.

* The efforts of the 12th century theologian, Thomas Aquinas, helped raise the practice of confessing sins to the level of a sacrament.

There are personal details about Gregorian chant:

* The chant developed in the early Middle Ages but was not named after Pope Gregory VII because he invented it but because he was a mentor of the music. Frankish monks and clerics developed it.

The rise of certain religious orders is told, showing them as responses to the problems of their generation:

* The monastic system took a dramatic turn in the 13th century, when St. Francis of Assisi founded his Franciscan order on three core points: poverty, humility and simplicity, “after the form of the holy gospel.” It was intended as a return to the literal imitation of Christ, in a religious environment of pomp and circumstance.

Kung’s proposals for the future of unity for all Christians are aptly untypical. Reinstate Martin Luther as a Catholic, he advises. The 16th century monk and founder of the Lutheran Church was excommunicated for his part in the Protestant Reformation.

The unification of Eastern and Western Christian churches depends on the Vatican, he believes. Language, cultural and liturgical differences may have contributed to the 12th century schism.

“The theory and practice of Roman primacy is the main cause of the split between Eastern and Western churches,” Kung concludes.

By the end of this massive history, Kung has put the entire Christian tradition through its own Inquisition, apocalypse and resurrection. Fortunately for all concerned, it is strong enough to take it.