The Muslim poet Rumi suggested that we live with a deep secret that sometimes we know, then not, and then know again. That’s a good description of faith. Faith isn’t something you nail down and possess once and for all. It goes this way: sometimes you walk on water and sometimes you sink like a stone.

The Gospels testify to this, most graphically in the story of Peter walking on the water. Jesus asks Peter to step out of a boat and walk across the water to him. At first it works. Peter, unthinking, walks on the water, then becoming more conscious of what he is doing, he sinks like a stone.

We see this too in the massive fluctuations in belief that Jesus’s disciples experience during the “40 days” after the Resurrection. Jesus would appear to them, they would trust he was alive. Then he would disappear and they would lose their trust and go back to the lives they’d led before they met him: fishing and the sea. The post-Resurrection narratives illustrate the dynamics of faith pretty clearly: you believe it. Then you distrust. Then you believe it again. At least, so it seems on the surface.

We see another example of this in the story of Peter betraying Jesus. In Mark’s Gospel, Jesus tells us that there is a secret which separates those who have faith from those who don’t: “To you is given the secret of the kingdom, but to those outside everything exists in parables.”

That sounds like gnosticism, that is, the idea that there’s a secret code somewhere (eg, The Da Vinci Code) that some know and some don’t, and you are in or out depending upon whether you know it. But that’s not what Jesus is saying here. His secret is an open one, accessible to all: the meaning of the Cross. Anyone who understands this will understand the rest of what Jesus means, and vice versa. We are in or out, depending on whether we can grasp and accept the meaning of Jesus’s death.

But being in or out isn’t a once and for all thing. Rather, we move in and out. After Peter denied Jesus, we’re told: “he went outside”. This is intended both literally and metaphorically. After his denial, Peter stepped outside a gate into the night to be away from the crowd, but he also stepped outside the meaning of his faith.

​How to continue reading…

This article appears in the Catholic Herald magazine - to read it in full subscribe to our digital edition from just 30p a week

The Catholic Herald is your essential weekly guide to the Catholic world; latest news, incisive opinion, expert analysis and spiritual reflection