From a news point of view, Francis' visit to a Rio slum Thursday, telling the poorest of the poor that "the church is with you," may be the highlight of his July 22-28 Brazil trip.
In terms of visuals, the vast crowds sure to gather for the youth vigil Saturday night and the final Mass Sunday morning, both now set against the picturesque backdrop of Rio's Copacabana beach, will certainly be stunning.
It's quite possible, however, that for Francis himself, the most important thing he'll do all week comes Friday morning, when he moves across town to Rio's Boa Vista Park to hear five confessions.
Every pope seems to have a signature spiritual idea. For John Paul II, it was courage: "Be not afraid!" was his catchphrase to invite the church to recapture its missionary swagger after years of introspection and self-doubt. For Benedict XVI, it was "faith and reason," the idea that religious belief and intellectual reflection need one another to remain healthy.
For Francis, the best early candidate for his signature touch is mercy, expressed in his repeated emphasis on God's endless capacity to forgive.
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Confession, of course, is the church's premier sacrament of mercy, so Friday, Francis is both substantively and symbolically going to the heart of his own spiritual message.
In a recent essay for the Italian newspaper Corriere della Sera, Enzo Bianchi, founder of the celebrated ecumenical monastery of Bose, offered a statistical analysis of the words used most frequently by Francis since his election. He found that the single most commonly used term was "joy," more than 100 times, followed closely by "mercy," which the pope has used almost 100 times.
Francis made mercy the heart of his first homily at the Vatican's parish church of St. Anne's on March 17, and he returned to it later that day in his first Angelus address.
"For me, and I say this humbly, the strongest message of the Lord is mercy," Francis said at Mass.
Reflecting on the accusations directed at Jesus in the Gospels of consorting with sinners, Francis said: "Jesus forgets. He has a special capacity to forget. He forgets, he kisses, he embraces, and he only says, 'Neither do I condemn you; go, and from now on sin no more.' "
"The Lord never gets tired of forgiving, never," Francis said. "We are the ones who get tired of asking him for forgiveness."
It's not something that simply occurred to Francis the morning after his election. Instead, it's consistent with his pastoral outlook developed over a lifetime, which has always emphasized the need for Christ's representatives to exude mercy and compassion.
"Only someone who has encountered mercy, who has been caressed by the tenderness of mercy, is happy and comfortable with the Lord," Jorge Mario Bergoglio said in 2001.
"I beg the theologians who are present not to turn me in to the Inquisition; however, forcing things a bit, I dare to say that the privileged locus of the encounter is the caress of the mercy of Jesus Christ on my sin."
Over the years, Bergoglio occasionally took strong stands to back up what could come off as pious talk. In September 2012, for instance, he delivered a blistering attack on priests who refuse to baptize children born out of wedlock, calling it a form of "rigorous and hypocritical neo-clericalism."
The importance of mercy is also expressed in the motto Francis has taken as pope: Miserando atque eligendo, which means, roughly, "by having mercy and by choosing."
In the Angelus address the pope delivered at Castel Gandolfo on July 13, he returned to the theme.
"God always wants mercy for everyone, and not condemnation," the pope said.
"He wants the mercy of the heart because he is merciful and understands well our suffering, our difficulties and even our sins. He gives this merciful heart to all of us."
Indeed, there have already been so many references it's actually tough to choose the most representative.
His Urbi et Orbi message for Easter Sunday, for instance: "God's mercy can make even the driest land become a garden, can restore life to dry bones."
Or his message for Divine Mercy Sunday on April 7: "Trust in the Lord's mercy; he always awaits us, loves us, has pardoned us with his blood, and pardons us every time we go to him to ask his forgiveness."
Given this emphasis, Francis has always had a special passion for confession. When he visited Saints Elizabeth and Zechariah Parish on the northern outskirts of Rome on May 31, for instance, he heard several confessions before saying Mass, something John Paul and Benedict didn't do on their trips to Roman parishes.
Both John Paul and Benedict did, of course, hear confessions in Rome during Lent, and they also heard confessions from pilgrims during previous World Youth Days.
When Francis does it Friday morning, however, it'll have the feel of something more than routine papal activity. Instead, it will be perhaps the closest he comes this week to cutting to the heart of what he wants his pontificate to be all about.
(Follow John Allen on Twitter: @JohnLAllenJr)