Let me begin with the following:
Peter’s Role as Vicar of Christ’s Church Proved from Scripture
In John 21:15-19, the resurrected Christ, commands Simon Peter three times to “feed my lambs” and “tend my sheep.”
15When they had finished eating, Jesus said to Simon Peter, “Simon son of John, do you truly love me more than these?” “Yes, Lord,” he said, “you know that I love you.” Jesus said, “Feed (bosko) my lambs.” 16Again Jesus said, “Simon son of John, do you truly love me?” He answered, “Yes, Lord, you know that I love you.” Jesus said, “Take care of (poimanao) my sheep.” 17 The third time he said to him, “Simon son of John, do you love me?” Peter was hurt because Jesus asked him the third time, “Do you love me?” He said, “Lord, you know all things; you know that I love you.” Jesus said, "Feed (bosko) my sheep.
In this passage, we can see that Jesus leaves Peter in charge of feeding, tending and caring for His sheep. Who feeds, tends and cares for sheep? A shepherd!
Unfortunately, many non-Catholics object to the Catholic understanding that Peter was given this unique leadership position, and they cite a passage from earlier in this same Gospel wherein Jesus presents Himself as the Good Shepherd, and says there is to be but “one flock and one Shepherd.” (John 10:11-16) Therefore, the immediate question springs to mind: If Christ is the Good Shepherd, why can’t He “feed” and “tend” His own sheep?
Of course, Jesus is God, and He is clearly capable of taking care of His own flock – even after He ascends to heaven. So, why does He appoint Peter to this role? Obviously, all sheep belong to Christ, and they do not cease to belong to Jesus after the ascension. Yet, Peter is told to “feed” and “tend” them. Jesus commissions Peter to act as His “stand-in” or “vicar” after the ascension. Jesus will remain the one Shepherd, yet Peter will “feed” and “tend” the sheep, in the sense that Jesus will not be physically present to do it. Thus, Peter will be the visible, vicarious shepherd of the flock.
Because of the implications of this earthly authority and the unique Catholic claims for the papacy, non-Catholics seek alternative explanations for Jesus’ words. One attempt is to claim that Peter simply has the same authority to care for the flock of Christ that all of the other apostles had. However, this argument fails for two reasons.
First, the extent of the authority Jesus gave to Peter can be seen quite clearly in the original Greek. For example, the word which is used for “feed” in John 21 is bosko – a word which the Jewish historian Philo of Alexandria, and other 1st Century writers, use to denote “spiritual nourishment.” Similarly, the word “tend” is poimanao – the same Greek word which is translated as “rule” in passages such as Matt 2:6, Rev 2:27, Rev. 12:5, and Rev. 19:15, where it is applied to Jesus Himself. Peter, like Jesus, is to “rule” over the sheep, and to “supply them with spiritual nourishment.” Thus, Peter is established as the vicarious shepherd (i.e., “supreme pastor”) of the Church in Christ’s physical absence.
While it may be argued that any shepherd would have similar responsibilities for his sheep and that the Bible is full of passages using the relationship between sheep and shepherd as a metaphor for our relationship with God, in the context of the New Testament, only Peter received this unique appointment directly from Christ Himself. Jesus took great care to identify Peter’s new responsibility as head of the Church with His own role as Head of the Body, the Church. No other Apostle received this focus.
Second, in Luke’s Last Supper account, we see quite clearly that Peter was singled out to play the role of a leader and unifier among the Apostles. The passage is as follows:
“Simon, Simon, behold Satan has demanded to sift all of you like wheat, but I have prayed for you that your own faith may not fail; and once you have turned back, you must strengthen your brothers. 33But he replied, “Lord, I am ready to go with you to prison and to death.” 34Jesus answered, “I tell you, Peter, before the rooster crows today, you will deny three times that you know me.”
In Luke 22:31-32, Satan sought to destroy all of the Apostles, but Jesus prayed for Simon Peter alone that Peter might strengthen all of the other Apostles whose faith would be shaken, as well. Clearly, Peter is not merely “one Apostle among others.” Rather, he is also responsible for the welfare of all. That is a special ministry – the ministry of the vicarious shepherd. No other Apostle is given the responsibility for caring for the Twelve in this way, and this assignment is all the more significant when we consider that in the following verses (v. 33-34), Jesus predicts Peter’s three-fold denial. Despite Jesus’ foreknowledge of Peter’s denials, Jesus prays for and assigns to Peter the task of caring for the others.