One of the many blessings of the Second Vatican Council is its affirmation that the doctrine of the church develops. From the days of the apostles, the bishops wrote in “Dei Verbum,” Christians have been exhorted to “hold fast to the traditions which they have learned either by word of mouth or by letter (see 2 Thes 2:15), and to fight in defense of the faith handed on once and for all (see Jude 1:3).” At the same time, the bishops went on to say, the apostolic tradition “develops in the church with the help of the Holy Spirit. For there is a growth in the understanding of the realities and the words which have been handed down. This happens through the contemplation and study made by believers, who treasure these things in their hearts (see Lk, 2:19, 51) through a penetrating understanding of the spiritual realities which they experience, and through the preaching of those who have received through episcopal succession the sure gift of truth. For as the centuries succeed one another, the church constantly moves forward toward the fullness of divine truth until the words of God reach their complete fulfillment in her.” Pope Benedict XVI expressed this truth succinctly, when he observed in his 2009 letter to those who refused to accept the teachings of the council, “The church’s teaching authority cannot be frozen in the year 1962.” Pope Francis often cites St. Vincent of Lerins, a fifth-century monk and author who taught that doctrine progresses through consolidation and expansion. The point is that doctrine attempts to articulate the truth of the Christian faith. While the truth does not change, the way it is expressed can develop. During the interview on his flight back from Canada last year, Pope Francis observed that “a church that does not develop its thinking in an ecclesial sense is a church that is going backward.” Citing the words of the late great American scholar of the history of Christianity, Jaroslav Pelikan, the pope called attention to the difference between “tradition” and “traditionalism.” “Tradition,” Pelikan wrote, “is the living faith of the dead, traditionalism is the dead faith of the living” (“The Christian Tradition: A History of the Development of Doctrine”). He later explained in an interview that “tradition lives in conversation with the past, while remembering where we are and when we are and that it is we who have to decide. Traditionalism supposes that nothing should ever be done for the first time, so all that is needed to solve any problem is to arrive at the supposedly unanimous testimony of this homogenized tradition.” Yes, we need to be in conversation with the past and treat our tradition with great respect, as G.K. Chesterton wrote. “Tradition is the democracy of the dead. ... Democracy objects to disqualifying people by the accident of their birth; tradition objects to their being disqualified by the accident of death. Democracy tells us not to neglect a good man’s opinion, even if he is our groom; tradition asks us not to neglect a good man’s opinion, even if he is our father.” At the same time, a core teaching of our tradition is the need to discern in every age the movement of the Holy Spirit, calling us to a deeper understanding of the truths of our faith. During an April meeting with Jesuits in Budapest, Pope Francis summed up a proper understanding of how doctrine develops by offering this image from nature: “The flow of history and grace goes from the roots upward like the sap of a tree that bears fruit. But without this flow you remain a mummy. Going backwards does not preserve life, ever.”