How often have you heard that Catholicism can’t be true, or that the doctrine of papal infallibility can’t be true, because of this or that sin of a particular pope? It’s a common misunderstanding, as if the truth of Catholicism required the personal sinlessness of every successive bishop of Rome.
But in fact, a biblical view of the papacy shows that Jesus established it to work amidst the all-too-human failings of St. Peter and his successors.
One of the striking things about the Bible is that the men God chooses are so obviously flawed. Peter describes God as saying of King David, “I have found in David the son of Jesse a man after my heart, who will do all my will” (Acts 13:22), and yet the Old Testament is unflinching in describing David’s fallings, particularly his adulterous relationship with Bathsheba, leading to his murder of her husband Uriah the Hittite (2 Sam. 11-12). The prophet Nathan goes so far as to tell David that by his sins he had “utterly scorned the Lord” (2 Sam. 12:14), and yet he remains the true king of Israel and a man after God’s own heart.
Peter is no exception to God’s practice of using flawed instruments. He denied Christ three times (Matt. 26:69-75), and even after the Resurrection was famously rebuked by St. Paul in Galatians 2. And yet these things do not undermine Christ’s decision to choose Peter as the leader of the apostles and the first pope. Indeed, we see Christ’s choice for Peter precisely amidst these moments of weakness.
Arguably the clearest (yet often overlooked) passage pointing to the papacy is Luke 22:24-34, which takes place at the Last Supper. The apostles are arguing amongst themselves about which of them is greatest (22:24), and Jesus responds by explaining true greatness:
“The kings of the Gentiles exercise lordship over them; and those in authority over them are called benefactors. But not so with you; rather let the greatest among you become as the youngest, and the leader as one who serves. For which is the greater, one who sits at table, or one who serves? Is it not the one who sits at table? But I am among you as one who serves” (22:25-27).
He then turns to Peter and says, “Simon, Simon, behold, Satan demanded to have you [plural], that he might sift you [plural] like wheat, but I have prayed for you [singular] that your faith may not fail; and when you have turned again, strengthen your brethren” (22:31-32), Since in English we don’t have words to distinguish the second-person singular from the second-person plural, we miss an important switch. Jesus is saying that Satan has demanded to have all twelve of them, to sift them all like wheat. And Jesus’ response to this isn’t to pray for all twelve of them but to pray for one of them, Peter, that his faith might not fail, and then to entrust him with the task of strengthening his brethren.
By themselves, these two verses would be an impressive case for the papacy. Jesus explicitly entrusts Peter with the care of the other apostles in a unique way. But it’s yet more striking in the broader context of Luke 22. Immediately after saying that true leadership is service, and calling upon the apostles to serve, Jesus entrusts Peter with the task of serving even the other apostles.
But the moment it looks like things are going well for Peter, they come crashing down again. (This is a common theme. For example, Peter is the one whose faith was strong enough to let him walk on water . . . until it wasn’t.) Immediately after Jesus entrusts the care of the apostles to him, Peter responds by saying “Lord, I am ready to go with you to prison and to death,” leading Jesus to say, “I tell you, Peter, the cock will not crow this day, until you three times deny that you know me” (22:33-34). This brings out the paradoxical dimension of Jesus’ command, “when you have turned again, strengthen your brethren”: Jesus is entrusting the care of the Church to a man whom he knows is about to fall.
This is also present in Matthew 16, in the much more famous passage about the papacy. Peter confesses the true identity of Christ, saying, “You are the Christ, the Son of the living God” (v.16). Jesus responds,
“Blessed are you, Simon Bar-Jona! For flesh and blood has not revealed this to you, but my Father who is in heaven. And I tell you, you are Peter [Petros], and on this rock [petra] I will build my church, and the powers of death shall not prevail against it. I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven” (vv.17-19).
Much ink has been spilled over the question of who or what is the rock upon which Jesus will build his Church. An answer to this seems to come in John 1:42, in which we learn that the original name that Jesus gives Peter isn’t the Greek Petros but the Aramaic Cephas, a name that simply means “Rock.” But again, this high point for Peter is immediately followed by a fall, and so we see in the next few verses Peter trying to keep Jesus from dying (v.22), leading Jesus to say “Get behind me, Satan! You are a hindrance [skandalon] to me; for you are not on the side of God but of men.”
It’s here of all places that we get an ironic answer to the question of who the rock is, because a skandalon is a “stumbling stone.” In other words, Peter is simultaneously the rock upon which the Church is built (through his faith) and a scandalizing stumbling stone (through his failings).
In the words of Fr. Joseph Ratzinger, the future Pope Benedict XVI, “Has it not remained this way throughout all Church history, that the pope, the successor of Peter, has been petra and skandalon, rock of God and stumbling stone all in one?” What was true of Peter has been no less true of his successors.
The Protestant Reformer John Calvin laughed off Catholic appeals to papal authority in Luke 22 by saying
the thing is too childish in itself to need an answer: for if they insist on applying everything that was said to Peter to the successors of Peter, it will follow, that they are all Satans, because our Lord once said to Peter, “Get thee behind me, Satan, thou art an offence unto me.” It is as easy for us to retort the latter saying as for them to adduce the former.
What Calvin missed is that this is the whole point. The papacy isn’t the rock because the popes happen to be so holy or brilliant. Several times in history, the papacy has endured seemingly despite the pope. We might want a papacy in which every pope is sinless, or at least a future saint. But the papacy was founded by Jesus, who once said of his hand-picked apostles, “Did I not choose you, the twelve, and one of you is a devil?” (John 6:70).
In his first epistle, with what might be a touch of irony, Peter quotes Isaiah 8:13-14 to show that Jesus himself is both a petra and a skandalon, calling him a "stone that will make men stumble, a rock that will make them fall” (1 Pet. 2:8). So we should take care not to be scandalized by Christ and his decision to use the papacy and to allow the Chair of Peter to be occupied by sinners. After all, it’s his peculiar love for sinners that allows us to have the confidence to “draw near to the throne of grace, that we may receive mercy and find grace to help in time of need” (Heb. 4:16).
 Freimut und Gehorsam, trans. Heinrich Freis Fundamental Theology, 473
 Institutes of Christian Religion, Book 4, Ch. 7