Is the Pope Really Infallible?
Catholicism maintains that the pope is infallible, incapable of error, when he teaches a doctrine on faith or morals to the universal Church in his unique office as supreme head. When the pope asserts his official authority in matters of faith and morals to the whole church, the Holy Spirit guards him from error.
Papal infallibility doesn’t mean that the pope can’t make any mistakes. He’s not infallible in scientific, historical, political, philosophical, geographic, or any other matters — just faith and morals.
It boils down to trust. Catholics trust that the Holy Spirit protects them from being taught or forced to believe erroneous doctrines by preventing a pope from issuing them.
Whether the Holy Spirit’s intervention is as subtle as getting the pope to change his mind or as drastic as striking him dead, in any event, Catholics firmly believe that God loves them and loves the truth so much that he would intervene and prevent a pope from imposing a false teaching upon the whole Church.
This belief doesn’t mean that personally and individually the pope is free from all error. He could privately be wrong as long as he doesn’t attempt to impose or teach that error to the universal Church, because at that point the Holy Spirit would somehow stop him from doing so.
Infallibility is widely misunderstood. It’s not the same as the Catholic beliefs of inspiration or impeccability:
Inspiration is a special gift of the Holy Spirit, which He gave to the sacred authors, those who wrote the Sacred Scripture (the Bible), so that only the things God wanted written down were written down — no more, no less. So the pope isn’t inspired, but Matthew, Mark, Luke, and John were when they wrote their Gospels.
Impeccability is the absence and inability to commit sin. Only Jesus Christ, being the Son of God, and His Blessed Mother had impeccability — via a special grace from God. Popes aren’t impeccable, so they’re capable of sin — which, by the way, was visible in the case of the first pope, St. Peter, when he denied Christ three times just before the Crucifixion (Matthew 26:69–75).
Everything the sacred authors wrote in the Bible is inspired, but not everything every pope says or writes is infallible. Infallibility means that if the pope attempts to teach a false doctrine on faith or morals, the Holy Spirit prevents him (even by death) from imposing such an error on the faithful.
So, for example, no pope can declare, As of today, the number of commandments is nine instead of ten. Nor can he declare, Jesus was not a man or Jesus was not the Son of God.
Infallibility also doesn’t mean perfection. Infallible statements aren’t perfect statements, so they can be improved so that subsequent popes can use better or more accurate language. Yet infallible statements can never be contradicted, rejected, or refuted.
So according to Catholicism, an immoral pope (you’ll find several in Church history) can sin like any man and will answer to God for his evil deeds. However, as supreme head of the Church, the pope retains his infallibility on matters of faith and morals as long as he remains pope.
No pope in 2,000 years has formally and officially taught an error of faith or morals to the universal Church. Individually, some may have been poor or inadequate theologians or philosophers, and some may have had erroneous ideas about science.
That has nothing to do with papal infallibility, however, because the main objective is to preserve the integrity of Catholic faith for all the members at all times and in all places.