The Gospel reading for today in the ordinary form of the Roman Rite is Matthew 16:13-20. It contains one of the most famous passages from the New Testament: "You are Peter (Kepha), and on this rock I will build my church, and the gates of hell shall not prevail against it." I am not concerned here to explicate the sense in which that verse supports the Catholic doctrine of the papacy. That would only invite a debate that has and will continue to take place in countless forums, including this one. I am much more interested in the attitude the verse ought to encourage in every Christian.
Jesus' commissioning of Peter as the Church's "rock," as "Rocky," in response to Peter's inspired confession of faith, was deeply ironic. Peter was impulsive and inconsistent. At one point, Jesus addressed him as "Satan" for rejecting the idea of the Passion; as the Passion got underway, Peter thrice denied knowing Jesus. But all this is exactly what one should expect of a God who saved us by letting us put him to death in the most shameful way imaginable at the time. God meets us in our worst depths to elevate and transform us; in his humanity, he was raised up on the third day from the status of dead criminal to that of immortal King of the Universe. In his own small but indispensable way, Peter recapitulated that in his transformation, after Easter and Pentecost, from coward to rock of the Church.
The same should go for each of us in our individual journeys of conversion. I know what it is like, in my own little way, to be cast out, criminalized, and shamed to the depths; I know what it is like to be loved, elevated, and transformed by Our Lord precisely in and out of such circumstances. It is all part of the process of theosis, of being made into a god by participating in the eternal kenosis of God. The mold of the old self is broken and remade into something new and incomparably better, just as Peter was.
The Church herself is like that. She is a "perfect society" not because her members are perfect; far from it. She is the perfect society because, as the Mystical Body of Christ, she is the medium in which her members are taken in their brokenness and made whole on the model of the Passion and Resurrection. If people would come to see "church" in that way, rather than as just an institution whereby a bunch of people with similar religious opinions worship and do other things together, there would be a lot less disputing about the full meaning of Matthew 16:18.