It was said of John Paul II, as we left Ireland today, that he could turn a race track into a church and a church into a theater. He had, indeed, transformed the Galway Racetrack yesterday into a vast open-air cathedral and a number of churches he visited into places of theater with worldwide audiences.

And last night, in the rain and fog of Boston, he turned the Common into another massive scene of emotion -- surely one of the most unusual scenes that has taken place in that area of American history where they still celebrate the shot heard round the world.

The communion in the rain that marked his arrival in America will be remembered for many things -- the historic nature of a pope's first true official visit to the United States, the size of the crowd, its tone and temper. But, in the end, what was more important than a tangible count of people or a measure of applause and sound was an intangible. It was why nearly a quarter of a million people would stand for hours in a driving rain in perfect harmony and spirit, so oblivious to such foul weather.

They had waited patiently for hours under lower skies. They sang "The Battle Hymn of the Republic." They sang "Amazing Grace." But it wasn't until the pope finally arrived that the cloudburst began.

And it made no difference at all.

You couldn't hear those cheers that greeted his arrival-- the exuberance of the feeling conveyed -- without being struck again at the hold John Paul seems to exert on many people. Perhaps it's his freshness, perhaps it's a simple matter of faith, perhaps it's plain curiosity about wanting to see someone who has been so publicized as being unusually charismatic. I suspect, though, that John Paul radiates a kind of vitality and humanity that seems missing from so many public figures.

He is an actor, trained in the theater, published as a playwright, and his dramatic ability by now is well known. It has been on display, all these past days.

This isn't said in a cynical spirit. No one could witness the enormous emotional gatherings in Ireland, with their sudden explosions of sound and even more stirring silences without being affected by the chemistry between this pope and his people. What seems more important, though, is the role the "Polish Pope" from Rome is playing.

John Paul is the first pope to exploit the possibilities of the television age. A predecessor, Paul VI, whom he so obviously reveres and in many ways patterns himself after, was the first to move out of the narrow confines of the Vatican onto the world stage of foreign travel. But Paul, a frail ascetic, burdened with age and the stultifying traditions of the long line of Italian popes, lacked the vitality and presence that John Paul brings to the throne of Peter. There's no doubt the present pope, beginning his American tour, intends to use television and all the media to advance his views and increase his influence.

But what's most striking so far about John Paul is the mixed nature of that message. He's been both highly conservative and dramatically bold, heightening the sense of anticipation of those wondering how he will handle himself in America -- and, more important, how his message will be received here.

In his extraordinary 52-hour visit to Ireland, John Paul brought as radical a message as Jesus did to Palestine 2,000 years ago. He directly challenged those in the prevailing political structure. Catholic and Protestant, to put aside hatred and prejudice and begin anew. When he said he would not accept the widely held belief that the bloodshed in Ireland represented a religious war, he linked his own prestige with a hoped-for solution of the Irish problem.

"True Catholic and Protestants," he said, "as people who profess Christ, taking inspiration from their faith and the gospel, are seeking to draw closer to one another in unity and peace.

"When they recall the greatest commandment of Christ, the commandment of love, they cannot behave otherwise."

He repeated this theme of religious reconciliation when he said: "May no Irish Protestant think the pope is an enemy, a danger or a threat. My desire is instead that Protestants would see in me a friend and a brother in Christ. Do not lose truth that this visit of mine may be fruitful, that this voice of mine may not be listened to.

His passionate appeal for an end to the sectarian violence and the killing, made wherever he went in Ireland and which is surely to be restated at the United Nations tomorrow, stamps John Paul as a pope who wants to be felt as a force in world affairs.

At the same time, he has been preaching orthodoxy -- precisely the sort that some within the church fear will lose him followers in the United States after they have heard him.

Already on this journey he has admolished nuns and priests not to adopt modern garb, and has strongly restated the church's stand against abortion and divorce. He has indirectly come out against birth control by saying, "Marriage must include openness to the gift of children," and warned women against the demands of secular careers, advising them that their greatest role is motherhood. And he has counseled youth against the "lure of pleasure," particularly in "the sexual domain."

His pronouncements were generally welcome in Catholic Ireland, but their appeal in an infinitely more complex and diverse United States may prove to be something else.

The first impression is that John Paul's celebrated style will wear well.

When he began to deliver his first major American address -- aimed primarily at youth and students -- he was interrupted time and again by sustained cheers.

But the greatest roar came when he said, "I want to tell everyone that the pope is your friend . . . ." The rest of his words were drowned out in the cheers. He repeated the refrain from "America the Beautiful" -- and again he was interrupted. The pope then, smiling widely, said in his heavy accent, "Even if its rains."

Obviously, the long journey and the wearying hours have done nothing to diminish his timing and skill at moving great numbers.