Q. I know that the pope’s infallibility is not a personal trait but is part of his office as the successor of St. Peter. Even so, is every encyclical infallible?
A. The short answer is no. Vatican I’s decree “Eternal Pastor” taught: “The Roman Pontiff, when he speaks ex cathedra, that is, when discharging the office of pastor and teacher of all Christians, and defines with his supreme apostolic authority a doctrine concerning faith or morals that is to be held by the universal Church, through the divine assistance promised him in St. Peter, exercises that infallibility which the divine Redeemer wishes to endow his Church for defining doctrine concerning faith or morals.”
Infallibility is a guarantee that neither the pope teaching individually as the Church’s supreme pastor nor the pope teaching in communion with the whole college of bishops can mislead the faithful on an issue essential to salvation.
Encyclicals remain very important teaching documents. No pope since 1870 has designated an encyclical as an exercise of papal infallibility, which requires three conditions: 1) the subject is a matter of faith or morals, 2) the pope must be teaching as supreme pastor, and 3) the pope must indicate that the teaching is infallible.
Since 1870, the only such teaching is the 1950 definition by Pope Pius XII of Mary’s assumption. Some people have argued that every canonization is an infallible statement, but that opinion is not official Church teaching.
Recent encyclicals have been addressed to the whole Church, but the 2013 edition of Our Sunday Visitor’s Catholic Almanac lists 288 encyclicals since 1740, most of them written to bishops of a single country. Many of them were drawn up for the anniversary of a saint, a Holy Year, or another Church event.
Pope Leo XIII wrote the most encyclicals: 86 between 1878 and 1902. Blessed John XXIII broke new ground when he addressed Peace on Earth (1962) to the usual audience and added “all people of good will.”