And this is the testimony of John, when the Jews sent Priests and Levites from Jerusalem to ask him, "Who are you?" He confessed, he did not deny, but confessed, "I am not the Christ." (John 1:19-20)
It sounds odd to hear a negative phrase, 'I am not' described as a confession, yet the word is used twice. He confessed and did not deny. Yet when John says what he is not, he is saying this in view of the Christ who is to come. It is only the Christ, who can truly say 'I am'.
John is confessing the inadequacy of his humanity to say who he is. He can only say who he is not, and the priests and Levites are asking a deeper question than they know. Jesus says 'I am' and the implication of his divinity is unmistakable to any Jew. Only God can say 'I am', the words with which he reveals himself to Moses from the burning bush in chapter three of the Book of Exodus.
The 'I am not' of John the Baptist is revealed to be truly a confession of the 'I am' of Jesus the Christ. It is not a denial but the affirmation of the truth.
As created human beings, we can never truly say who we are. We are always prone to change, we can fall into sin at any time, we can rise from sin at any time, we are weaker than we know but sometimes we are stronger than we would believe. John learned this harsh truth in the desert, that until the one who is to come has been revealed, even his own identity is hidden from him.
Yet when this one comes, he does more than reveal his own self. He begins the long process of teaching us who we are, and he begins with Peter. He tells Peter that he will be called Rock. A little later he will proclaim Nathanael as an 'Israelite in whom there is no guile'. As the Gospel makes clear, he always knew what was in the human being.
Peter has less wisdom than John. He thinks he knows himself but no-one can know themselves unless they know not only what they are now but what they will be. To know oneself, it is necessary to know our whole life -- something we cannot do, because no-one can stand outside of their own life.
So Peter insists that he will lay down his life for Jesus, but Jesus replies that before the cock crows three times, he will betray him. Of course we know that he does. Yet Jesus also tells Peter that though he cannot follow him now, he will follow him later.
There is an important truth here. Jesus reveals Peter to himself, not because self-knowledge is interesting, but because he has a purpose which he intends to fulfil. He will bring Peter to be the Rock. The rock is who he truly is, yet also what he is to become. The best of a human being is what they truly are, and salvation is becoming what we truly are -- as long as we remember that what we truly are is what is to be revealed by God. Salvation is becoming what is prepared for us by the grace of God, while damnation is an alienation from our own selves.
It might seem that the final chapter of the Gospel of John belies this claim because here the Risen Jesus asks Peter to make a statement about himself. He asks him if he loves him more than these. Yet all three times, Peter answers not in terms of his own knowledge but in terms of Jesus and his knowledge: 'You know that I love you', twice and then a final, 'Lord, you know all things, you know that I love you.'
Jesus then goes on to show that his knowledge of Peter is more than a knowledge of his personality because he predicts the nature of his death -- the death by which Peter would give glory to God. When Our Lord tells Peter how he would die, he reveals to him a love which is more than a particular feeling he has at the time. It is the love which will shape his life, which will bring him to his true self.