A young man who left the Catholic Church for another church said, 'I couldn't stay in a church that cared more about rules than people'. It saddened me because he couldn't see that rules only matter precisely because people matter. Rules may make us uncomfortable, but should the latest trends change them simply to put people at ease? Things that make us uncomfortable lead to a choice: between listening to Jesus or to ourselves.
In John's Gospel many are uncomfortable with Jesus's teaching. They cannot accept that Jesus is the Bread from heaven, and many who had previously followed him cease doing so. Jesus interrogates his disciples, whether they also want to leave. Peter answers,
Lord, to whom shall we go? You have the words of eternal life; and we have believed, and have come to know, that you are the Holy One of God. (John 6.68-69)
Jesus responds by calling one of his apostles (Judas) 'a devil'.
This is similar to the Gospel we hear today. Jesus interrogates his disciples, 'But who do you say that I am?' and Peter responds with a confession of faith, 'You are the Christ, the Son of the living God.' Jesus then calls one of his apostles (Peter) 'Satan'.
In John's Gospel the reason for Peter's faith is that Jesus has 'the words of eternal life,' and in Matthew's account because Jesus's Father has revealed this to Peter. In both Peter has faith in God's saving revelation of himself. By contrast Judas is called 'a devil' (slanderer) because he rejects faith and life offered in Jesus, and Peter is called 'Satan' (adversary) because he is 'not on the side of God, but of men'.
Trust in God's saving revelation is the life of faith and discipleship, but rejecting this for human goals is to be a slanderer or adversary to God's will.
The context of these choices, between faith and one's own will, is an uncomfortable disquiet. The disciples do not understand Jesus's words or who he is, but they must choose. Peter puts his trust in Jesus. Following Peter's confession of faith, Jesus makes his own choice. 'Upon this Rock I will build my Church,' Christ says. But what is this Rock?
The Bible gives three identities for the Rock, and all three are true.
First, the Rock is Jesus himself (1 Corinthians 10.4). The Church is built on apostles, with Christ as chief cornerstone (Ephesians 2.20), such that there is no other foundation but Christ (1 Corinthians 3.10-11).
Secondly, the Church in her liturgy, on the feast of the Chair of Peter, unhesitatingly affirms that the 'Rock' is Peter's confession of faith. This seems a Protestant thing to say, but it is not. It is entirely Catholic.
Thirdly, the 'Rock' is Peter himself. Jesus says to Simon and no one else, 'You are Rock and on this Rock I will build my Church'. This is the plain literal sense of the text. Peter, shifting and fickle as sand, is made to be a Rock by Jesus. By grace Peter receives that stability and role that is Christ's by nature.
By the Father's gift the Church remains faithful, confessing through the Spirit that 'Jesus is Lord'. The young man I mentioned earlier wanted a church that changed its rules to suit people. But if any church should prefer human ways over God's or unbelief over faith, changing doctrine to suit people, then she is 'Satan' and 'a devil', the adversary and slanderer of Christ.
Founded by Christ, the Catholic Church is preserved from this by the gift of the Holy Spirit, uniting her in charity, united visibly on the fulcrum that is Peter. On this Rock has Christ built his Church.
Peter's ministry is therefore an inalienable gift of Jesus to the Church and to all Christians. By Christ's prayer Peter's faith does not fail, and turning he strengthens his brothers and sisters (Luke 22.32). The gift that is Peter is not overcome by 'the powers of death'.
We are protected from the shifting sands of the trends of any age because Peter is divinely graced, and no trend or fashion has ever loved and cared for his people more than God himself.