What does infallibility mean when referring to the pope?

Answer 1

Another answer from our community:

When the pope speaks ex cathedra (from the chair) on matters of faith and morals he speaks infallibly - without error. Such pronouncements are very rare and made only after years of study and in consultation with all the bishops. The only two times I am aware of this being used by a pope in recent centuries are the doctrine of the Assumption of the Blessed Virgin Mary and the doctrine of the Immaculate Conception. Once such a pronouncement is made the doctrine becomes incorporated into the beliefs of the Catholic Church.

Answer 2

According to Catholic belief, the First Vatican Council in 1870, defined when the pope is and is not infallible, in Pastor Aeternalis. Chapter 6 says:
9. Therefore, faithfully adhering to the tradition received from the beginning of the christian faith, to the glory of God our savior, for the exaltation of the Catholic religion and for the salvation of the christian people, with the approval of the Sacred Council, we teach and define as a divinely revealed dogmathat when the Roman Pontiff speaks EX CATHEDRA, that is, when, in the exercise of his office as shepherd and teacher of all Christians, in virtue of his supreme apostolic authority, he defines a doctrine concerning faith or morals to be held by the whole Church, he possesses, by the divine assistance promised to him in blessed Peter, that infallibility which the divine Redeemer willed his Church to enjoy in defining doctrine concerning faith or morals. Therefore, such definitions of the Roman Pontiff are of themselves, and not by the consent of the Church, irreformable. [My emphasis in bold]

In chapter 4 of the same document, the council appears to have limited that infallibility, by limiting the pope to jealously guarding and explaining what was handed down through the apostles, and not the ability to disclose a new doctrine by revelation:

6. For the Holy Spirit was promised to the successors of Peter not so that they might, by his revelation, make known some new doctrine, but that, by his assistance, they might religiously guard and faithfully expound the revelation or deposit of faith transmitted by the apostles.

The council may not have intended to have one clause limit the other in this way. The pope's pronouncement on the Assumption of the Virgin Mary was certainly not handed down through the apostles, so even if the pope is indeed infallible on certain matters Bishop Geoffrey Robinson (Confronting Power and Sex in the Catholic Church) believes this clause means that the pope was assuming an infallibility he did not have in this case. Critics of the doctrine of infallibility, such as Bishop Robinson, need further persuasion as to just when the pope is infallible and on what grounds.

The dogma of papal infallibility comes from the first vatican council of 1870 and means that when the pope makes statements 'Ex Cathedra', they are an unquestionable part of Catholic dogma. This faculty has been invoked once since its official definition in 1870. In 1950 Pius XII proclaimed the dogma of the bodily Assumption of Mary into heaven. But it was used in 1854 by Pius IX to declare that Mary is the Immaculate Conception. Papal infallibility was defined in 1870, but that does not mean that it came into existence in 1870. Whatever statements have been made by popes that meet the defined criteria are believed to be infallible teachings, no matter when they were made. Studies have been made of papal proclamations going back through history, and there are several such proclamations that are, or very probably are, infallible.

Not only is it rarely invoked, but infallibility is a conservative faculty. In other words, a statement made ex cathedra is no more and no less than error free. There is no presumption or requirement that the statement as made explains fully, in every detail and for all time the whole nature of the thing being taught. Ex cathedra statements are not beyond further clarification through later statements, by the same pope or following popes. Of course, such clarifications will not contradict the ex cathedra teachings that have already been made.

Although the Catholic Church attaches a great deal of reverence to their popes, they have never been considered impeccable, that is, unable to sin or make mistakes, as demonstrated by Pope John Paul II's apology for some of the church's persecutions in past history. When popes express personal opinions, even when those opinions deal with faith or morals, there is no requirement to believe those opinions. Only statements that meet the requirements of the definition of 1870 can be considered infallible.