The cult starts here. You wouldn't notice unless you looked hard. It has its origins on the back of a visiting card tucked in among candles and photographs of the late Pope at a makeshift shrine in the middle of St Peter's Square. In Spanish it says: "Saint John Paul II, intercede for the health of your son".
The late Pope created more saints than all of his modern predecessors put together, some of them, such as Josemaria Escriva, the founder of Opus Dei, in double-quick time. But even he never created a saint overnight.
Yet so intense is the sense of loss, so powerful the cult of personality that sprung up around Karol Wojtyla soon after he was elected Pope in 1978 and that kept on building for 26 years, that that in effect is what is happening here. From suffering vicar of Christ, re-enacting by his own slow and agonising death the Calvary of Jesus (as many devout people here saw it), he has leapt with one bound into the ranks of the saints.
The business card with the pregnant message was among dozens of prayers and love letters, photographs, children's paintings, painted hearts, bunches of daffodils and lilies and many, many candles on and around an ornate wrought iron lampstand in the piazza.
Katja Raithel, 29, a German tourist, said she remembers being made to stay silent by her mother as they listened to the Pope's Easter Mass on a crackling radio. "We will surely have affection for the next one, but this Pope will stay in our hearts," she says.
More votive offerings arrive with every moment. People turn up, deftly add their own candle or message or photograph to the mounting, teetering pile, then step back and kneel in prayer, or turn as if abashed and quickly walk away. A small group hovers around the shrine, a still point within the large, endlessly shifting crowd in the square; they peer, sniff the flowers, squint to read the messages, lingering, as if here, if nowhere else, they can still be close to him.
It is as if, in the minds of many of the devout, the persons of suffering Jesus and suffering John Paul II have been superimposed. The most common photograph to be tucked in among the others here is of Michelangelo's marble masterpiece inside St Peter's basilica, a couple of hundred metres from here, of the Virgin Mary holding the lifeless body of her son in her arms.
"Papa" - Italian for Pope - reads one message, "you have suffered much for our sins. We pray to you, we wish you to rest in peace." It's as if faith in Jesus and God, in these secular times, is a challenge too far - while faith in that amazing old man who only last Wednesday gasped for breath and strove to speak at the high window in the Apostolic Palace high above this square, comes easy. Nobody really knew him, apart from a small, tight-knit group of intimates, mostly Polish priests and nuns and professors. Yet millions felt they knew him well, so powerful was his charisma. And that intense but somewhat unreal emotion - like the fake sense of intimacy we enjoy with secular celebrities and royalty - survives his death unscathed.
"He made the Church more human, closer to the real people," says Giorgio Arduini, there to pay his respects on behalf of his wheelchair-bound wife. He claims not to be a practising Catholic but says he "felt deeply" the Pope's suffering.
Yet Karol Wojtyla is gone now, physically, and the difference that makes in the mood of this beautiful, embracing Renaissance piazza is immense. While he lingered up there in his bedroom, slipping in and out of consciousness, his body temperature and blood pressure bouncing up and down, his breath growing shallow, there was no other possible focus for the attention of pilgrims than his suffering person.
In the piazza, everyone reflexively turned in the direction of that window, or kneeled or sat or stood in groups singing hymns facing it. The silence on Thursday and Friday evenings was unreal: so many thousands here, of every age and condition and many nationalities, occupying the square without special ceremony or formality, but so quietly that the loudest sound was the splashing of the ornate fountains.
Then he died, the announcement came over the loudspeakers, and the silence was total. It was broken - and this wouldn't happen in Britain, it would seem shockingly inappropriate - by a round of applause. Let's hear it for the grand old gentleman.
And it was at that moment that the tension was broken. He had been released. His sufferings were at an end - and ours, too, on his behalf. There were tears, of course, rivers of them, for his loss but, within minutes of the end, people were able to talk of joy, too.
"I feel sad because he's gone," said a woman walking through the crowd with her husband and baby, "but I feel joy, as well, because he has been liberated from his suffering."
Yesterday, the piazza was a different place completely. The Pope had been liberated and Rome had been liberated, too. The Pope's corpse might be lying in state in the Sala Clementina inside the Apostolic Palace - tomorrow it moves to the basilica, where the public can pay their last respects - but the living focus was gone: that room was just a room again, that window just a window.
Families traipsed along the traffic-free Via della Conciliazione eating ice-creams, pushing buggies, walking their dogs. In the corner of the square closest to the palace where he had died, a lively chorus sang modern hymns, some loud and exuberant, with drum and tambourine, and clapping.
"Giovanni Paolo!" they chanted, as if on the football terraces. "Giovanni Paolo, [clap clap clap], Giovanni Paolo!" "Alleluia!" they sang, loud and clear. There was no longer any call to be quiet.
You couldn't help but be sad.