Father J. Bryan Hehir, the former head of Catholic Charities and of the Harvard Divinity School, arrived a smidge late Thursday to the Kennedy School class he teaches on the ethics of war and tried to jump straight into his planned lecture on humanitarian military intervention.

His students, however, had other ideas. "Can you talk about the pope, please?" one asked.

Hehir is one of the most interesting thinkers in the Catholic Church, so of course he could: When the charismatic Pope John Paul II first stepped out onto that loggia overlooking Saint Peter's Square right after he was chosen to lead the church, "he overwhelmed the crowd." When scholarly Pope Benedict XVI ventured onto the balcony, "he taught the crowd," and when humble Pope Francis "stepped onto that platform," Hehir said, "he related to the crowd." What that shift will really mean, for and far beyond the world's 1.2 billion Catholics, no one knows.