from The Great Reformer – Francis and the Making of a Radical Pope by Austen Ivereigh, p. 111, 113.
While
reading Denzinger's Enchiridion—a widely used collection of church
teachings—Bergoglio had been struck by an early-church formula of Christian
faith: that the faithful people was infallible in credendo, in its
believing. The Vatican Il document, Lumen Gentium, had recast the Church not as
an institution so much as a people, the "People of God"; from
Denzinger he had grasped that the "people" was also a repository of
faith. As Bergoglio later wrote: "When you want to know what the Church
teaches, you go to the Magisterium . . but when you want to know how the Church
teaches, you go to the faithful people. The Magisterium will teach you who is
Mary, but the faithful people will teach you how to love Mary." 
In his first
talk as provincial, Bergoglio would use this notion to reject ideologies, From
now on, the idea would appear constantly in his writings. The “pueblo fiel”
were both vaccine and antidote, the hermeneutic of a true reform.
……
Bergoglio … was not a theologian and was wary of being ensnared by labels. But his own view of history, both national and Christian, pointed him in the same direction, In the idea of "God's holy faithful people" Bergoglio had what theologians call a hermeneutic—an interpretative key, or yardstick—that would allow him to reform and unite the province, beyond ideology, by focusing very directly on the poor. It was neither conservative …nor clerical: he did not believe that the clergy, or the bishops, or Rome were in possession of the truth that they distributed downward, but that the Holy Spirit was revealed through a dialogue between the pueblo fiel and the universal Church. It was a radical stance, an option for the ordinary people, the fishermen and shepherds to whom God revealed Himself in Jesus Christ two thousand years ago.
