The ability to know and have a relationship with the living Christ is both a mystery and a grace, something which Christians understand interiorly, not through mathematical proofs, Pope Francis said Friday.

“Jesus is the Son of God: therefore, He is perennially alive as his Father is eternally alive,” the pope said June 29.

“This is the novelty that grace ignites in the heart of those who open themselves to the mystery of Jesus: the non-mathematical certainty, but even stronger, interior, of having met the Source of Life, the life itself made flesh, visible and tangible in the midst of us.”

Pope Francis spoke about a Catholic’s experience of the mystery of Jesus before leading the Angelus in St. Peter’s Square for the Feast of Saints Peter and Paul, the patrons of Rome.

He explained that this knowledge, that Christ is eternally alive and present, is not something a person experiences on the merit of being Christian, but it is a gift of grace from the Trinitarian God: “Father and Son and Holy Spirit.”

Francis reflected on the day’s Gospel reading from Matthew — when Jesus asks his disciples, “who do you say that I am?” — explaining that “all of this [mystery] is contained in a seed in St. Peter’s answer: “You are the Christ, the son of the living God.”

Just as in the Gospel, when the disciples tell Jesus the different interpretations people had of him at the time, “over the centuries, the world has defined Jesus in different ways,” Francis said.

These definitions, he said, include, “a great prophet of justice and love; a wise master of life; a revolutionary; a dreamer of the dreams of God ... and so on.”

But amid the confusion of these and different hypotheses on the identity of Jesus, Peter’s confession, “humble and full of faith, stands even today, simple and clear,” he said: “‘You are the Christ, the Son of the living God.’”

Continuing, the pope explained that following Peter’s answer, Jesus makes him the head of his Church, pronouncing the word, “Church,” for the first time in the Gospels, “expressing all the love towards it, which he defines as ‘my Church.’”

Jesus establishes the community of the New Covenant, which is based on faith in him. “A faith that Blessed Paul VI, when he was still Archbishop of Milan, expressed with this admirable prayer,” he said, concluding his address by quoting the prayer.

“O Christ, our only mediator, You are necessary for us: to live in communion with God the Father; to become [one] with you, that you are the only Son and our Lord, your adopted sons; to be renewed in the Holy Spirit (Pastoral Letter, 1955).”