Protestants, when they hear the pope is infallible, often take this to mean he is impeccable. They believe that the Catholic Church teaches that the pope cannot sin. Some Protestants take it to mean that the pope relies on some kind of divine inspiration when declaring doctrine infallibly. Both of these perceptions are flawed. Papal infallibility means that the pope cannot err when teaching solemnly or definitively on a matter of faith or morals. Although the bishops have the gift of infallibility when they maintain the bond of unity between themselves and the Pope and teach definitively on a matter of faith or morals, and bind the Church to accept it, the Pope has this charism as an individual. The words of Jesus, which apply to the Apostles, and by extension, their successors–the bishops: "He who hears you hears me" (Luke 10:16), and "Whatever you bind on earth shall be bound in heaven" (Matt. 18:18), apply in a special way to Peter and his successors–the Popes, "Whatever you bind on earth shall be bound in heaven" (Matt. 16:19). Here, Peter and the Apostles are told that when they teach on an issue of faith and morals, their teaching is ratified in heaven, because they have the gift of infallibility and cannot teach error, and because the Holy Spirit was sent to guide them "into all the truth" (John 16:13).
The pope teaches infallibly when he clearly defines a doctrine on faith or morals, while speaking ex cathedra, or as supreme pastor and teacher of the faithful–not just as a private theologian, binding the Church to that doctrine thereby.
Papal infallibility does not mean the Pope is inspired to say exactly what God wants him to say, as the Biblical writers were, but rather, he is protected from saying something untrue, something that God would not want him to say. Infallibility does not imply that the Pope knows Scripture and the Catholic faith better than anyone. It also does not mean that the Pope can formulate new doctrines–he may only defend, define, or explain doctrines that were held since the Apostolic Age. The Pope may make imprudent decisions on matters not related to faith and morals, and may fail to declare the truth by keeping silent, but neither of these have any bearing on papal infallibility. Popes may contradict other Popes on disciplinary matters, and in their private opinions. But each Pope is bound by prior infallible teachings–he has no power to change, delete, or add doctrine.
In order to refute papal infallibility, Protestants point to Galatians 2:11-16, where Peter refused to eat with Gentiles, according to the obsolete Jewish Law, for fear of offending certain Jews. The fact is, Peter's cowardly actions were a disciplinary matter. He was certainly not making an ex cathedra statement on the binding of the Mosaic Law, because Galatians 2:15-16 makes it quite clear that Peter knew the correct teaching. Even though Peter denied Christ (Mk 14:66-72) and made a fool of himself at the Transfiguration (Mk 9:5), he still had the charism of infallibility when he wrote his two epistles. It is not a big stretch, therefore, to believe that Peter was also given that charism of infallibility when he made an ex cathedra statement regarding faith or morals.
Protestants usually focus on history. To debunk the idea of papal infalliblility, Protestants cite cases of papal errors. 1. "Zozimus (418) declared Pelagius orthodox, but later declared him a heretic." Declaring one to be orthodox or heterodox is not an exercise in infallibility. If the heresies of Pelagius were taught by Zozimus, that would be a different story altogether. 2. "Pius VII (1814) restored the Jesuits, who were suppressed by Clement XIV (1773)". This was a disciplinary matter, not a teaching on faith or morals. 3. "Sixtus V (1590) declared a translation of the Vulgate riddled with errors to be valid". Once again, this has nothing to do with teaching a doctrine concerning faith and morals. 4. "John XXII (1331), said no one would see the Beatific Vision until the General Judgement". John XXII did say this in a sermon, but also said that it was only his private opinion, and retracted this teaching on his deathbed. 5. "Boniface VIII (1302) said in the bull Unam Sanctum that to be saved, one must be subject to the Roman Pontiff". This statement is true, but what Boniface failed to mention (because it should be understood without having to state it directly) is that the invincibly ignorant are excused. For those who are not invincibly ignorant, subjection to the Roman Pontiff is necessary for salvation. The correct interpretation is that those who are not invincibly ignorant must be subject to the Roman Pontiff. 6. "Pope Leo X, in the bull Exsurge Domine comdemned the position that it is against the will of the Holy Spirit that heretics be burned at the stake." This is true, but at the time, almost all heretics were revolutionaries, much like the communists of the twentieth century, and were a threat to society. The Catholic Church does teach that capital punishment is not immoral.
Protestants usually refer to three cases, which they say best proves their point. In the first example, they claim Liberius, in 358, professed an Arian creed in order to become Pope. Of course, if he did do this, it was done before he became Pope, and therefore papal infallibility does not apply. Some claim he did this while he was Pope. What really happened is that Liberius, under duress, signed an ambiguous statement that could be interpreted either in an orthodox or an heretical sense. Besides, he signed only as a private theologian, and did not bind the Church to it. In the second example, fundamentalists claim that Vigilius, in 548, failed to condemn certain Monophysite writings, and when the Council of Constantinople met, he gave into pressure from the bishops there and condemned the Monophysites. In reality, the Eastern bishops signed a document that condemned the Three Chapters, which supported the Nestorian heresy (the belief that Christ is the fusion of two men), but favored the Monophysite heresy (the belief that Christ had only one nature–the divine). At first, Vigilius would not condemn the Three Chapters, and when he finally did condemn them, he retracted soon thereafter. But when the council met, he gave in and condemned The Three Chapters, along with the other bishops. All along, Vigilius supported the orthodox teaching. In the final example, Protestants claim Honorius supported the Monothelite heresy (which holds that Christ only had one will–the divine). What really happened was that the Patriarch of Constantinople, who was a Monothelite, wrote to Honorius in Greek, a language which he could not understand, and for which he had poor translators. The Pope replied that the Patriarch should not discuss the issue, but the Patriarch interpreted his letter to mean that the Pope supported the heresy, and was allowing the Patriarch to continue to teach it. Honorius was put on a list at the ecumenical council as a Monothelite heretic, posthumously. No council has any authority apart from the Pope, and the Pope presiding over the Council declared that Honorius was not condemned because he supported the Monothelite heresy, but because he refused to condemn it.
But the fact is, history supports papal infallibility. Not only do we have the absense of any examples of papal infallibility gone wrong (with the exception of a few bogus cases), but we have the testimony of Cyprian, who supported the age-old doctrine of papal infallibility when he said, "Would the heretics dare to come to the very seat of Peter whence apostolic faith is derived and whither no errors can come?"