Only once in my lifetime has a pope seemed anything other than impersonal. All other times he's been a character in some remote medieval pageant who makes an occasional brief appearance, wrapped in splendor amid muted ceremony, and then quickly disappeared from sight and mind.

I say that as a non-Catholic, but I suspect many younger members of the faith feel the same way. Even in Rome, I know, young Italians often are in the habit of referring to the pontiff as something of an irrelevance. "Papa," they remark: Papa will take care of this or that. They say it with an air of humorous affection mixed with a certain sardonic cynicism.

The exception was both notable and memorable. Not for 624 years had a pope had the name John, but when the portly figure of John XXIII entered the world stage in 1958 my perception of the papal office and the potentially of its role changed.

Other popes of memory had even looked alike - austere, ascetic, unsmiling, pale solemn and slim - men of the public corridors. John XXIII was of a different mold. With his jowls and prominent Roman nose and look of supressed laughter about his eyes, he exuded warmth and humanity. John 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.

It wasn't just his personal characteristic, his modesty and wit, that made him so compelling a pope, John proved to be bold and innovative. Thought at first to have been merely a transitional figure, he turned out to be the leader of a religious revolution.

here were 52 members of the College of Cardinals when he took the throne of St. Peter, 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. In the next four years he added 32 more cardinals. The total tthen was the highest in history and gave the princes of the church their most international cast ever.

The exumenical movement, of course, is John's greatest achievement. In the early '60s, when so many things seemed possible, that ecumenical spirit captured 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 tolerence, of freedom of thought and action. Mourning for him was genuine and spontaneous. I was only one of the many, many non-Catholics who felt a personal sense of loss that spring of 1963.

It's unfair, I'm sure, but my impression of the papal figure of Paul VI these past 15 years has been of a return of the distant anonnymity of the past tradition of popes. Paul's sharp features and quiet demeanor even strongly resembled John's predecessor, the taciturn Pius XII.

My colleague Colman McCarthy persuades me that is an incorrect judgement. Not only did Paul travel moe than any people, he was an activist at a time when great issues - and great changes - were rising throuhout the world.

As American combat forces first began moving through the elephant grass into action in Vietnam, he journeyed to the United States and denounced was and militarism. 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 that "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 so many years past.

Yet the impression of him - and I believe it to be widespread among laymen and younger Americans - seemed uniformly negative.

At a time when the church was losing youth, nuns and priests, and when dramatic change swept through the structures of organized religion and societty at large, it was Paul VI who was seen as a pope stubbornly clinging to the past.

Ten years ago this summer he issued his most controversial pronouncement. His rigidity in denouncing the pill and other forms of artificial birth control set off a bitter debate within the church, one 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 that his was a reactionary papacy.

He undoutedly deserves better, but it was his fate to follow an extraordinary leader and to preside over a period of extraordinary change.

If recent popes have seemed distant and largely ceremonial figures, there's a good reason. They have been old men in an age dominated increasingly by the fashions of youth.

Seven men have reigned as pope since 1900. None was born in the 20th century. Four were in their 80s when they died; one was in his 90s. Only one came to the 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 65.

They have all been old men and all Italians.

The opportunity for change in age and nationality and approach, exists. How that choice is resolved poses the most intriguing question arising out of the ancient ritual we are now witnessing. Not until that white smoke goes up over the Vatican, signaling the selection of a new pope, will we have any clues as to what extent the church moves in new direction - or stands firmly with the status quo.