THE CATHOLIC CHURCH, once a mighty fortress, God's presence on earth as well as a latter-day extension of the Roman Empire, now seems to be lying in ruins, its walls breached by new barbarian hordes.

Religious have abandoned their vocations as never before; the laity, once submissive and docile sheep, now flaunts its independence. Papal authority has been redefined and modified, when not disregarded. Discord is rampant. The center -- the pope, Peter's successor -- has not held.

Or has he? Is the Catholic Church, like the rest of society, finally falling apart? Or is it merely undergoing a traumatic transformation, its chaos a harbinger not of collapse but of new life? Will it continue to speak to men as it has for nearly two millennia?

To these crucial questions, four recent books on the papacy and the Catholic Church provide thoughtful and provocative -- albeit incomplete -- answers.

In The Papacy Today, Francis X. Murphy, rector of Holy Redeemer College, in Washington, and an expert at Vatican II, is cautiously optimistic about the church's efficacy in the modern world. The apparent chaos in the church Murphy interprets as signs of an identity crisis, a prelude to essential change. Murphy is far too informed and wise to be disturbed by the church's outward reluctance to shift its position on numerous doctrinal issues. Change has always been rife in the church, and the church has always done its utmost to deny it. Unlike most institutions, which boast of change, the church, Murphy writes, follows a different, more Byszantine line, which he baptizes "Rynne's Law" (after Xavier Rynne, author of Letters From Vatican City ). About to accept a mutation in doctrine or discipline, "the whole edifice of tradition" first denies even the possibility of change. Then with the publication of a papal or hierarchical document "that expresses a refusal to budge on the issue, an unwitting acknowledgment has been made of the fact that the turnabout is already in progress."

The thrust of recent changes in the church has been outward. With the signing of the Lateran Treaty of 1929, the pope broke a self-imposed withdrawal from the world. Through Leo's XIII's Rerum Novarum ("Of New Things"), the Holy See began to show its deep concern for the social ills of modern man. Of course, by summoning the Second Vatican Council, John XXIII propelled Catholicism onto the contemporary stage. Change became a way of life. All roads now seem to lead from Rome to the world.

In addition to having both solid scholarship and an intimate knowledge of ecclesiastical politics, Murphy's study is honest and direct. Murphy calls one Vatican official a "garrulous dandy," recognizes the contradictions in John Paul II's message to Africa in which he exhorts Africans to be themselves, yet shrinks from addressing the fact of polygamy.

Murphy is the first to admit the church's blunders: Pope John Paul II's conservative stand on birth control, his refusal to laicize priests, his disciplining of theologian Hans Kung. Yet, in spite of all, emphasizes Murphy, the current pope seems to be the only world leader capable of bringing about the revolution in justice and peace "necessary to avoid a world conflagration." But, Murphy pleads, he must seize the moment -- otherwise the Holy Spirit "may intervene drastically with possibly a catastrophe the catalyst of unity."

In The Papacy in the Modern World, J. Derek Holmes, church historian at Ushaw College, near Durham, England, surveys much of the same ecclesiastical turf that Murphy measures. Holmes' major thesis is similar: marooned between two worlds, one dying the other not yet born, the church must respond now to its own crisis and to that of modern man. Holmes reminds those who forecast only doom that they ignore "the fact that the moral prestige of the Papacy... was stronger and more influential during the second half of the twentieth century than... at the beginning."

It is on the church's attitudes toward Jews during World War II that Holmes makes his most significant contribution. Referring to new materials released from the Vatican archives over the last 15 years, Holmes once and for all puts into perspective the stand of the Catholic Church and of Pius XII in particular towards Hitler's anti-Semitic policies.

In spite of their limitations, the Christian churches showed greater resistance to Hitler's policies than any of the other great German institutions, "such as the judiciary or the universities." In Dachau alone, more than 2,000 Catholic priests died or were murdered. Holmes' account of Catholic martyrs is inspirational. Asked what he thought of the Fuehrer, one Catholic priest retorted: "I have only one Fuehrer, Jesus Christ."

But the scandal persists. What about Pius XII? Surely he should have protested. He was, after all, pope. Why his silence? Hochhuth's The Deputy condemns Pius' moral cowardice. In more temperate language, historian Guenter Lewy (in The Catholic Church and Nazi Germany, 1964) states: "Finally one is inclined to conclude that the Pope and his advisors... did not view the plight of the Jews with a real sense of urgency and moral outrage. For this assertion no documentation is possible, but it is a conclusion difficult to avoid.... All things told, did not the murder of several million Jews demand a 'candid word'?"

To the contrary, Holmes' evidence exonerates Pius XII. Aware of Nazi atrocities, Pius XII judged that protestation would only have enraged Hitler to further slaughter and would have jeopardized the pope's own effects to save Jewish lives. Thus, with full knowledge, Pius XII elected to remain silent, though he risked, and subsequently did incur, the condemnation of the world -- if only he could save lives. And the pope was spectacularly successful. Throughout Rome, Jews were sheltered in ecclesiastical buildings. On the pope's instructions, many were dressed in clerical garb and taught to chant the liturgy. In Rome alone more than 30,000 Jews were saved by the church's interventions. A former Israeli consul in Italy claims that "The Holy See, the Nuncios and the entire Catholic Church saved some 400,000 Jews from certain death." After the war, the World Jewish Congress sent 20 million lire to Vatican charities to express its gratitude to the pope. As Holmes succinctly states: "Was his [Pius XII's] moral reputation more important than the life of a single Jew, or was the life of even one Jew more valuable than satisfying his conscience in the eyes of the world?" From such a risk Pius XII did not shrink. Now history is beginning to vindicate his quiet heroism.

At the heart of the church, Peter Nichols recognizes a spiritual anarchy, a center of mysticism and, ultimately, of unpredictability; thus, how effectively the church will deal with contemporary woes is impossible to state. Moreover, what today seems an unwise, ill-informed choice might in the future be hailed as progressive and epoch-making. The Pope's Divisions (the title is taken from Stalin's quip, "How many divisions has the Pope?") is a journalistic account of the fortunes of the modern church, written by the Rome correspondent of the London Times, himself a non-Catholic. In the form of lengthy feature articles on the papacy, the church and world problems, the church in the Third World, collegiality, and other topics, Nichols' book is laced with lots of gossip, ecclesiastical jokes and stories, and numerous personal experiences. Though his statistics sometimes obfuscate the issue and retard the reader's progress, Nichols, always chatty and voluble, is generally interesting and informative. His work abounds in metaphors that are occasionally strikingly apt. Nichols views the Catholic Church as Wagnerian, "in the sense that it is richly varied and flows in a controlled but seemingly endless stream." It also produces "more apologists than do other great religions. Mozart has no apologists." "In musical terms, the papacy is fugal," he writes. The Synod of Bishops is "a Sleeping Beauty awaiting a papal kiss to arouse it to full dominance."

Reflecting on his own experiences and epiphanies, Nichols is at his delightful best. He is least trustworthy when commenting on the gospel or when endeavoring to wring more significance and symbolism from a personal experience than seems warranted. He goes awry when he himself pretends to Wagnerian grandeur.

Where Murphy and Holmes and even Nichols fear to tread, Malachi Martin sprints. The Decline and Fall of the Roman Church is a witty and lively you-are-there retelling and interpretation of church history. Martin's remarkable feat is that not a page of his book is dull. This account of Pope Leo the Great's encounter with Attila the Hun is typical of Martin's style and approach:

"Attila moves forward into the river from the northern bank. Both men are watching each other; Leo is now still, Attila advancing slowly. The distance narrows. Leo now sees Attila as an oldish man, with bent back, slanting eyes, rolling restlessly hither and thither, a lined face, narrow-lipped mouth.... The distance narrows. Their eyes meet. Attila barks a sudden question.

"'Your name?'

"'Leo.'"

The rest of the conversation has escaped even Martin. Leo's feat would be equivalent, Martin assures us, to Lyndon Johnson's walking on foot through the DMZ between North and South Vietnam in search of President Ho Chi Minh during the Tet Offensive of January 1968.

Martin focuses on key moments in church history: Constantine's establishment of Christianity as the official religion (the first mistake); Leo's miraculous saving of Rome; the clumsy treatment of Martin Luther; the definition of papal infallibility; the dissolution of the papal states; John. XXIII's convening of Vatican II. The thesis Martin relentlessly stalks on every page: when the church attempts to propagate the faith through material or political means, inevitably it declines. Now thanks to John XXIII who in five years "undid what every Pope since the fourth century had sought and fought to maintain," the church has been stripped of its political authority, disillusioned about its pretensions as possessing the military grandeur of the old Roman Empire. "John spoke amiably about opening windows... while actually and unwittingly, he was leveling the walls." The church has now only spiritual authority. That Martin emphasizes, and that alone is all Christ promised in the first place. Thus Martin's title is not as apocalyptic as it seems at first glance: the Roman church's decline he sees as a blessing.

Like Murphy, Holmes, and Nichols, Martin hails Pope John Paul II as the most compelling religious leader in the world today. The present Dalai Lama, the archbishop of Canterbury, Billy Graham -- "They don't matter, as John Paul matters." The church, however, must act now, and it must act in fidelity to the gospel. The church must, above all, love Christ, believe in his Word, and obey Him. Then "My Father and I will give you the lifegiving Spirit... he will be continually by your side... he will be in you all... because I live on, and you too will have life." The safety and continuance of John Paul's church depend, Martin writes, "finally and only, on that obedience and that belief. All else, in the perspective of religion, does not matter."