Strengthen your brothers

Luke 22:31-32 records Jesus telling Peter "Satan demanded to have you, that he might sift you like wheat but I have prayed for you that your faith may not fail; and when you have turned again, strengthen your brethren". The original Greek in the passage shows that Satan demanded to sift "you", or all of the apostles, but Jesus prayed specifically for Peter and his faith not to fail. 

Jesus singles out Peter and prays for him so that his faith may not fail and he would strengthen his brethren (Lk 22:31-32). Peter will be a leader, but one who serves others instead of being served. Trent Horn, The Case for Catholicism (Ignatius 2017).

1. To begin with, this passage says nothing about the papacy or the pope strengthening the Roman episcopate. It's not a promise to the papacy. It's not a general promise. It's very topical. 

2. Peter is singled out, not because he outranks the other disciples, but because he will betray Jesus. The prayer anticipates his denial. Jesus prays for Peter's restoration in advance of his betrayal.

3. As a matter of faith, Peter's faith did fail. He lost his nerve and publicly renounced Jesus. That's a paradigmatic act of infidelity. 

In context, the meaning of the statement is not that his faith will be unwavering, but that his failure won't be permanent. Jesus prays that Peter won't abandon the cause. Having betrayed Jesus, he will repent of his betrayal and renew his commitment. 

4. The text doesn't say how Peter will strengthen his fellow. The most immediate explanation, in context, is that the example of Peter's restoration will strengthen the other disciples. The source of encouragement is not something Peter will do, but something Jesus did for Peter. If even Peter can be forgiven and restored, after publicly disowning Jesus, that's an encouragement to the other disciples, as they face persecution in the years ahead. Indeed, one reason Jesus tells Peter, in the presence of the other disciples, that he has prayed for him, is so that when Peter is contrite and rejoins the movement, that outcome will be attributed to the prescient and efficacious intercession of Jesus rather than Peter's fortitude naturally rebounding. 

5. Finally, there's the fallacy of inferring that if Peter is said to strengthen the other disciples, this carries the implication that the other disciples won't strengthen each other. Catholic apologists act as though statements like this imply a contrast, where affirming something in reference to one person disaffirms the same thing in reference to anyone else. But the statement is not logically exclusive, as if only Peter can play that role. What makes Peter special in this passage is not his leadership but his failure of leadership. He buckled under pressure and set bad example. The proleptic prayer of Christ is to rectify Peter's dereliction, not to promote him.