The Romans, who ruled the world by imperial force secure in the belief of their divine right, surely thought they were removing a minor problem when, on the same day nearly 2,000 years ago, they crucified a man named Peter upside down in the Circus Neronianus and beheaded another Jew who also came from faraway Jerusalem, Paul, at the Aquae Salvine.

Three hundred years later another Roman emperor, Constantine, had a historic change of faith: He placed the cross on the banners of his legions and built the great Basilica over the tomb of Peter that was to stand as the center of Christendom, the place where the popes reign. And, in one of history's greatest ironies, as the empire was beseiged, declined and fell, it was the popes who preserved Roman law, Roman traditions, Roman majesty, and the popes who ruled amid all the glittering treasures and with all the grandeur of the Roman emperors of old. Their church, no less than the rule exercised by the emperors, embraced the world; and their control, like that of the emperors, has been absolute. For nearly two millennia they have been borrowing styles and systems, language and titles, customs and artifacts from the political monolith that was once their most bitter enemy. Their Roman Catholic Church, the oldest institution in the western world, remains the sole surviving heir of the Roman Empire.

It is with these facts in mind that you reconstruct the scene that formed in the moonlight almost exactly a year ago on the central balcony of St. Peter's Basilica.

The papal master of ceremonies, a monsignor in the Curia, the body that down through the centuries has administered church affairs in a tightly controlled, authoritarian and secretive manner, was introducing the newest pope to the throng massed below in the square. Ritual called for the pope to give a brief blessing in Latin. Instead, to the extreme discomfit of the Roman traditionalists surrounding him, he began making an unprecedented impromptu speech. Basta, the priest implored the pope. "Enough." But the pope continued to speak in a strong clear voice and with an obvious alien accent:

"I don't know if I can express myself well enough in your -- no, our -- Italian tongue," he said. "If I make mistakes, you will have to correct me."

As far as the crowd was concerned, the pope was making no mistakes. They roared out their approval.

An American Catholic scholar who teaches at Rome's centuries-old Pontifical Biblical Institute, Dennis McCarthy, was one of those in that huge crowd who felt stirred by what he was seeing and hearing. Like most of them, he felt something of a shock at the selection of the new pope. Father McCarthy was standing with a group of priests from other lands when the announcement that Cardinal Karol Wojtyla of Krakow, Poland, had been chosen pope was first made from that window.

"We wouldn't have known who he was unless someone had produced a list of cardinals," he recalls. "He was a complete blank; no one knew anything about him. What went through my mind was total surprise -- surprise that the cardinals would have picked a non-Italian, then a feeling of 'This can't be happening,' and then a feeling of 'Isn't this wonderful?' Not because he turned out to be a Pole, but because the church had broken away from hundreds of years of tradition and opened itself to something new."

At 7 o'clock the next morning, as is his custom, Father McCarthy walked down the narrow, winding street from the Biblical Institute to say mass at a small church facing the Fountain of Trevi (another celebrated Roman monument, which proclaims in heroic marble statuary and engraved inscription the blessings of clear, healthy water brought to the people of Rome by the three popes who ordered and financed the work). Next door to the church, as always, the street sweepers were gathering for their day's work. Their conversation was all about the new pope, and it was critical. "This Polac," Father McCarthy heard them say, "this stranger."

Every morning at the same hour for about a week their critical tone continued; then it changed. Now it was our pope the Italian workers were speaking about. "In a very short time, he had made himself acceptable to them," Father McCarthy says. Which, he discovered on a visit back to the States this past summer, was more than could be said of the pope's effect on many Catholic academics.

What Father McCarthy encountered in America is something also common here in Rome -- an attitude of uncertainty among many thoughtful members of the Catholic clergy (to say nothing of the populace at large) about where Pope John Paul II plans to lead the church in an age of challenges to all authority, including historic challenges from within the ancient Roman Catholic Church itself.

He found, as he puts it, "a suspicion, a fear" that the new, much-discussed, much-publicized, obviously highly charismatic and in many respects unconventional "Polish pope" might prove too inflexible and too conventional for the various strains facing the church as it approaches its third millennium.

Therein lies a paradox of historic proportions: the first non-Italian in almost five centuries as well as the youngest pope in more than 130 years now occupies the throne of St. Peter, a vigorous, strong and commanding figure, to be sure; yet his challenge may well be not so much how he commands as how well he leads, and not how non-Roman he seems but how well he succeeds in preserving the best of the old Roman style while at the same making room for something new and nonimperial in approach.

For whatever else you can say about this new pope who has already proved so different after only a year, as another Catholic scholar here remarked, you still can't separate the individual pope from the papacy.

To an American non-Catholic the idea of a pope -- the all-powerful, infallible person who sits as both supreme law-giver and supreme judge, proclaimer of dogma, dispenser of discipline -- continues to be breathtaking. But no more so than the physical manifestations of that assumption of power displayed here in Rome. Go to St. Peter's and you will see not merely the largest church in the world. You'll find, as you talk the length of that opulent cathedral, that the Romans have carefully marked, in gold, the various dimensions of other great churches in the world -- London, Rheims, Prague, Madrid, Constantinople -- all are inscribed in the center aisle by meters. It takes a good stroll before you even begin to reach the line showing the end of the second-largest church. And by the time you reach Michelangelo's great dome ("the greatest dome in the greatest cathedral in the world," a guide says to his touring group, all gazing upward) this invocation of size and power becomes not only awesome, but arrogant. This, too, springs straight from the Roman Empire.

Whenever the pope is called the "pontiff," the empire is being evoked: "Pontifex Maximus" ("The Greatest Bridge-Builder") is one of those titles the popes picked up directly from the emperors. Even the church's basic structure flows directly from the days of ancient Rome: "diocese" and "parish," the central administrative units of today's church, were civil administrative units of the empire.

Evolution of the all-powerful papacy was gradual. Bit by bit, century after century, the popes expanded their reach -- and their claims. They became Bishop of Rome, then Primate of Italy, then hundreds of years later the Vicar of Christ on Earth, Patriarch of the West and, finally, after a thousand years, the self-professed most august and omnipotent rulers of everything they surveyed, both church and state, the popes of the Universal Church. The assertion of powers claimed by one imperial pope, Hildebrand, Gregory VII, in his Dictatus Papae of 1075, remains as grand as any proclamation of any emperor:

The pope can be judged by no one; the Roman church has never erred and never will err till the end of time; the Roman church was founded by Christ alone; the pope alone can depose and restore bishops; he alone can make new laws, set up new bishoprics and divide old ones; he alone can call general councils and authorize canon law; he alone can revise his judgments; his legates, even in inferior orders; have precedence over all bishops; an appeal to the papal courts inhibits judgments by all inferior courts; a duly ordained pope is undoubtedly made a saint by the merits of St. Peter.

Out of such thinking came the long period of greatest papal power. The popes crowned emperors, commissioned holy wars, presided over the political and spiritual life of the Middle Ages. Inevitably, corruption existed. Some papacies were bought. Intrigues, assassination attempts and kidnapings occurred. At times several men claimed simultaneously to be the legitimate pope, each warring against the other. But whatever the internal traumas and whatever the external threats, including the historic split that led to the Protestant Reformation, the papacy survived.

In the centuries since, that papacy settled into a pattern that remained constant until well into mid-20th century life. The church was monolithic, and the popes presided with a firm but distant hand from Rome. They were all Italians, and nearly all old men. There had been a period, it seems, before the last century, when the pope was accorded less public respect than now. A Roman scholar, talking about the evolution of the papacy the other day, said he had been surprised to find that the great veneration for the pope is a fairly recent phenomenon -- historically speaking, that is. An 18th-century English traveler to Rome, for instance, wrote that people didn't even bother to tip their hats to the pope if his procession passed by.

To the world at large, the pope often appeared an impersonal figure, a character in some remote medieval pageant who made an occasional brief appearance, wrapped in splendor amid muted ceremony, and then quickly disappeared from sight and mind. In the 20th century the popes even seemed to look alike -- austere, ascetic, unsmiling men, pale and solemn and slim, heard singing the ancient Latin words of prayer in often thin and reedy tones. In a century increasingly dominated by the fashions of youth and the currents of revolutionary change, they remained old men suited more to the private chambers than the public corridors.

Until last year, seven men had regined as pope since 1900. None was born in this century. Four were in their 80s when they died; one was in his 90s. Only one came to the papal throne while in his 50s, and Benedict XV became pope just before his 60th birthday. The others entered the papacy at the ages of 68, 68, 64, 63, 76 and 85. They were, as it was often said, aged men who were "prisoners of the Vatican."

All this began to change when the portly figure of John XXIII entered the world stage in 1958. With his jowls and prominent Roman nose and look of suppressed laughter about his eyes, John exuded warmth and humanity. He was the good friar, jovial and affable, who cherished good living; he possessed the gifts of affection and compassion; he was open and accessible and conveyed a sense of welcome to all.

But it wasn't just his personal characteristics, his modesty and wit, that made him so compelling a pope. John proved to be bold and innovative. Though at first thought to have been merely a transitional figure, he turned out to be the leader of a religious revolution. There were 52 members of the College of Cardinals when he became pope, and 12 of them were in their 80s. John moved swiftly to change those numbers and their composition. His first consistory resulted in the annulling of church regulations that dated back to the late 1500s, and the creating of 23 new cardinals. That total then was the highest in history, and gave the princes of the church their most international cast ever.

John's greatest achievement, the one that truly opened the doors of the church to the modern age, was the calling of a Vatican Council designed, as he described the aims a decade ago, "to restore the simple and pure lines the face of Jesus' Church wore at its birth." His move met with stern resistance from the Roman traditionalists, but John persevered. As the 1960s began, Catholic commissions had started work on a number of sweeping reform proposals. Before the bishops of the world assembled in Rome in October 1962, John delivered a radio broadcast heard around the world spelling out in unmistakable terms the boldness of his vision. The council would be concerned, he said, with the entire human race, and with people's rights everywhere to freedom, justice and the good things of life.

The ecumenical movement, born of that aim, is probably the change John made that has been felt most widely outside his church. In the early 1960s, when so many things seemed possible, that ecumenical spirit -- promising to bring together in common purpose people of many faiths -- captures the emotions of millions around the world. John's reign lasted less than five years, but his imprint on people in and out of the church was profound. He cut through the mystical trappings of the papacy, humanized the role, made personal the impersonal and left a legacy of tolerance, of freedom of thought and action. His death in June 1963 brought spontaneous and genuine mourning, among non-Catholics as well as Catholics.

His successor, Paul VI, the former Cardinal Giovanni Battista Montini, was, it was said, born to be a pope. Steeped in the intricacies of Vatican operations and the workings of the Curia, trained as a papal emissary on important diplomatic missions, scholarly but with an affinity for and an association with the working man, Paul VI presided for 15 of the most difficult papal years in the church's recent history. He had none of the personal magnetism of John, but he even further accelerated changes within the church. If John had broken through the ring around the Vatican "prison," Paul made the world his personal ministry. Not only did he travel more than any pope in history, he was an activist at a time when great issues -- and great changes -- were rising throughout the world. CONTINUED ON FOLLOWING PAGE

As American combat forces first began moving through the elephant grass into action in Vietnam, he journeyed to the United States, the first pope ever to set foot on American soil, and denounced war and militarism before the United Nations. As the world noted the 20th anniversary of the bombing of Hiroshima, he called for the outlawing of the manufacture and storage of nuclear weapons. As the arms race continued to escalate, he stated publicly and forcefully that it was "unthinkable that no other work can be found for hundreds of thousands of workers than the production of instruments of death." As rich nations continued to exploit poor ones, he issued so strong a pronouncement on economic abuses and injustice that he was denounced as a socialist. Expropriation of private property was at times justified, he said, adding: "Private property does not constitute for anyone an absolute and unconditioned right. No one is justified in keeping for his exclusive use what he does not need, when others lack necessities."

These were hardly the words of a reclusive personality, or one seeking compromise over controversy. And it was under Paul's stewardship that the church embarked on liberalization in forms and practices of worship that would have been unthinkable not many years past. Yet toward the end of his reign the impression grew -- especially in some areas of America -- that he was a negative figure. Part of this was his age, his declining health and obvious frailty, his increasing querulousness and seeming pessimism, and part the difficult age in which he was fated to reign.

When the church was losing youth, nuns and priests, and dramatic change was sweeping through the structures of organized religion and society at large, it was Paul VI who was seen by many younger members of the priesthood and laity as a pope stubbornly clinging to the past.

In the summer of 1968, in the midst of a year of great turbulence in America and abroad, with assassinations, racial strife, war and student protests presaging what appeared to some as a breakdown of manners and morals, he issued his most controversial pronouncement. His rigidity in denouncing the pill and other forms of artificial birth control set off a bitter dispute within the church that has not yet been stilled. Paul's subsequent positions on such issues as abortion and the role of women in the church reinforced the accusations among more liberal elements of the church that his was a reactionary papacy.

The view one hears in Rome about Paul is far more favorable: "I think history will be kind to him," said one American Jesuit assigned to the Vatican. "He laid out a certain foundation and made it possible to change many things." At the same time, the problems facing the church had, if anything, increased in complexity.

Figures on departures from the church by priests and nuns are extremely hard to come by, but that significant moves have been occuring is certain. Soneone in the Curia who handles applications for leaving the church in the Jesuit order won't give concrete numbers, but speaks in terms of "internal waves." In the mid-1960s there were very large numbers leaving from Europe. In the late '60s and early '70s similarly large numbers were being recorded in North America. And toward the end of the '70s the waves were affecting the church in Latin America and India. The Vatican shows a loss of 30,000 priests worldwide in the years 1972 to 1979.

Church attendance was another problem. Again figures are not readily available, but one priest gives a personal example of what he knows is taking place: For nearly a quarter of a century he's been visiting a large parish in Nuremberg. In years past the church always was jammed on Sundays. Now he finds it notably empty, and hears the priest there tell him he thinks that only about 15 percent of Catholics in the area are now attending church, whereas in past decades it would have been virtually 100 percent.

These kinds of problems were confronting Paul VI when he died, at the age of 80, in the summer a year ago. His successor would have to deal not only with them, but also with increasing debate about such continuing questions as the role of women, birth control, divorce, celibacy and clerical dress. Again the cardinals convened, and again the white smoke rose from the chimney over the Vatican signaling a new pontiff; and again a different type from the taciturn popes of the remembered past emerged.

Another Italian cardinal appeared before the masses in St. Peter's Square, but a far more informal one. Albino Luciani, the son of a glassmaker, had a gentle, modest manner and a winning smile that warmed those who say him. His self-deprecating air permitted him to say of himself that he was a "poor wren," and people loved him for it. He paid honor to the two strong popes who had immediately preceded him and called himself, after them, John Paul I. But he was destined to leave behind a memory instead of a record, for his death after only 33 days as pope once more set off a search for a successor in a troubled era.

It took an untimely death and a political deadlock between two powerful Italian cardinals for the Church of Rome to break finally with its past. Someone so different in style and nationality was chosen that the world is still trying to assess just who now holds spiritual sway over more than 700 million Catholics around the glove and who represents a central core of organized religion. The drama inside the Sistine Chapel, where the cardinals select their popes in utmost secrecy, came down last October to one moment. Sitting alone beneath Michelangelo's Last Judgment was Karol Wojtyla of Krakow. "Do you accept?" he was asked in Latin.After what one account calls "an agonizing pause," Wojtyla replied:

"With obedience in faith to Christ, my Lord, and with trust in the Mother of Christ and of the Church, in spite of the great difficulties, I accept."

He was asked what name he would take as pope. After another pause, he said he would call himself John Paul II, thus linking himself to the acts and works, and personalities and beliefs, of the three last popes he has served. So much has been written already about John Paul II that it's becoming hard to separate the man from the legend. He makes news in everything he does, and seems to revel in it. The singing pope the skiing pope, the swimming pope, the acting pope, the traveling pope: He flouts tradition, he courts the crowds, he holds news conferences, he talks with reporters on his plane and in these things and many more conducts himself differently from any pope anyone has ever seen. He's a physical man who seeks a physical response, and gets it.

Not long after his elevation to pope a group of nuns surrounded him and tore at his cassock as if he were some hard-rock star touring town. In his first year, he's already made two extensive and emotional foreign journeys, to Mexico and then to his native Poland, and now is winding up what is the first true papal tour of America, including being the first pope to be received by a president in the White House. He's drawn such attention to himself, and generated such curiosity, that some within the walls of the Vatican privately and slyly refer to him as "Johnny Superstar" and "The Polish Ham." Concern is rather widely expressed that he'll become all style and little substance.

That would appear in error, for the more you talk to people here with insights about the church and the papacy, the greater grows the conviction that John Paul II could turn out to be a most strong pope indeed -- and, in terms of dogma and beliefs, not to the liking of some who now see him as a liberating force. Two themes keep coming up in the conversations about him: To understand him, you must ap preciate his particular personal background and that of the Polish church in general; and, for all his obvious warmth and feeling for people, John Paul II can be tough when it comes to conviction. Firm, very firm, are words repeated about him.

The point about Poland is not that he's a foreigner, but that the Polish Catholic Church represents an older, more dogmatic, more clannish, traditional brand of Catholicism. Through all the years of Communist domination of Poland since World War II, more than anything else it has been the fervent, unyielding stance of the church that kept the Polish people united. Partly because of necessity and partly because of custom, the church spoke with one clear voice as expressed by the old primate of Poland, Cardinal Stefan Wyszynski. If Wojtyla ever had doubts about the cardinal's views, no one seems to know it. And certainly he always maintained a total show of unity, making some wonder how he would brook the dissent that flares from various corners of the church worldwide.

His record thus far as pope has underscored a traditional approach. In his first weeks as pope he reaffirmed the traditional rule of celibacy for priests, told nuns he didn't like the idea of their wearing secular clothing in public, and said they should not permit any feminist claims to overshadow their call to a chaste, poor and obedient life. His first encyclical, framed around the subject of the nature of man and his destiny, also struck a traditional note in style and content. He discussed such themes as free-wheeling by Catholic theologicans, liturgical excesses, the indissolubility of marriage, individual confession and devotion to the Virgin Mary and the Mother of God.

"Nobody, therefore," he said, in words of a long familiar cast, "can make of theology, as it were, a simple collection of his own personal ideas, but everybody must be aware of being in close union with the mission of teaching truth for which the Church is responsible."

He has also told women that their greatest role is motherhood, and strongly restated the church's position against abortion.

Since these and other stands essentially restate familiar past positions, many here wonder whether they have heard John Paul's final word on the subjects. In fact, his positions so far have left uncertainty about where he's going ideologically. Again and again, Vatican priests say that no clear line has yet emerged from this pope. "We are waiting, waiting, waiting, but nothing happens," said one of them, a non-American. "We don't know the kinds of things he cares about. We don't know him. Nobody knows him. We don't know the thoughts of this pope."

That appears to be a common opinion, certainly stated in one form or another in numbers of interviews here. This attitude goes hand-in-hand with another forming about John Paul II: that no one seems to know who has most influence with him, or who his most influential counselors are. That represents a distinct break with tradition, for in the past the lines around the pope were drawn clearly and tightly. Now you hear vague talk of "a small group of Poles" counseling the pope. The truth is, few seem to know.

All this possibly comes under the heading of the grousing that normally accompanies any change in power, temporal or secular. The outs want in, the ins want to know the workings of the outs to maintain their positions. And some of the uncertainty simply comes down to a matter of this pope's personal style. "People come out from an hour or so audience with him feeling they've done all the talking," says the Rev. John Long, an American active in ecumenical affairs within the Vatican. "He hasn't let them know what he thinks. They get the impression he's primarily been getting information out of them. It's all their opinions. Nothing yet indicates a specific line."

But something more fundamental, and perhaps more important, is known about John Paul II. It has to do with his own character and his own view of his fellow men.

You can't watch this man without being struck by his magnetism. That's an easy term to use, particularly for journalists looking for the mystical chords of the mighty. Nonetheless, to see John Paul with people -- that mobile face, all creases and lines, strong jaw, furrowed brow, wreathed in smiles -- is to see a man who seems filled with an exuberance of life and a sensitivity toward others. He earns his public acclaim easily. People who knew him in Poland have testified he has a puckish sense of humor, and his students in theology and ethics in Krakow found him the kind of professor who treated them more as colleagues than pupils.

By now the basic details of his life are familiar: born in modest means May 18, 1920, in the town of Wadowice, about an hour's drive from Krakow at the foot of the Beskid Mountains in the Western Carpathians, near the Czech frontier; his father a junior officer in the Polish army, stern by all accounts, and his mother a school teacher before marriage. There was little money, and much heartbreak: his mother died giving birth to her third child, a girl stillborn, when Wojtyla was not yet 9. Not long after, his older brother, Edward, a doctor 15 years his senior, died of scarlet fever contracted from a patient. The boy, called "Lolek," and his father moved to Krakow. Three years later the father was dead and Wojtyla was without a family.

He had already shown unusual scholastic promise, and enrolled at Krakow's celebrated Jagellonian University as a philosophy student. It was in this period that he became passionately interested in the theater, and decided to become an actor and playwright, continuing his studies in literature. But for Wojtyla, as for all Poles, war intervened and changed his life.

Although the Germans closed the university, Wojtyla and a small group of students continued to study and meet secretly to recite Polish poetry and perform patriotic dramas before small groups of 15 or 20 people. He already had been exposed to a study of Christian mysticism, but, while working full time in a stone quarry, still had ambitions for the theater.

One day during that period a major event occurred. While crossing the street from his apartment, he was struck by a passing German truck, and his skull was fractured. In a delirious state, he found himself thinking for the first time of the priesthood. A few months later he narrowly escaped death in a worse accident when he was crushed by a truck, permanently leaving one shoulder higher than the other. Out of this complex of experiences came his decision to become a priest. As he later described them: "During the time I was a worker, the deepest questions of my life became crystalized: My humanistic, Polonistic, artistic interests . . . my literary interests, my artistic interests -- all that in some way boiled up in my soul and resulted in the priestly calling."

He became a brilliant scholar and expert in many languages, earning two doctorates in theology and ethics, and was strongly influenced by the work of the German philosopher Max Scheler.

Some here see this pope's humanistic spirit, and humanistic training, as the key to his papacy -- and to how he will address the larger questions involving science, genetics, changing work patterns, declining natural resources and new conflicts that mark the last secular years of this century.

"This man burst on the scene impressing people with his vitality, with his obvious strong beliefs," says the Rev. Vincent O'Keefe, former president of Fordham University and now a leading Jesuit attached to the Vatican. "To me, his central thing is a kind of Christian anthropology. He believes in Man. No matter who this man is or where he lives we should respect him. And that man has rights given him that everyone should respect. He can talk way beyond the confines of the Roman Catholic Church."

Perhaps the most intriguing aspect of this unusual pope concerns his writing. For 16 years, while a Catholic leader in Poland, Karol Wojtyla published poetry in two Catholic journals there under a pseudonym. Reading over the translation of those poems, from the last copy in a bookstore near the Vatican, shows another side of the new pope. He writes about workers, and suffering, and love, and the frustrations of people trapped in jobs they despise. Great poetry they may not be, but as private musings of someone whose words now will be heard around the world, they are illuminating. Here's one stanza only, from a poem entitled "The Car Factory Worker" Smart new models from under my fingers: whirring already in distant streets. I am not with them at the controls on sleek motorways; the policeman's in charge. They stole my voice; it's the cars that speak. In the ancient days, a priest here recalled, there was an old saying that spoke to the condition of the church and the rest of the world: "Rome is far, and the Pope is old." Those facts may have existed for ages, but in this day of jet travel and instant mass communications, and in this period of a new kind of pope in Rome, they no longer seem relevant.