In Sunday's Gospel selection, Saint Peter says, "Lord, to whom can we go? You have the words of eternal life. We have come to believe and know that you are the Holy One of God."
In the context of what was happening that day, Peter's statement is remarkable. In effect, he was saying, "Despite the conclusion of all those who have turned away, despite the centuries of synagogue teaching, despite the improbability of any human being embodying the words of life, we believe that you, Jesus, have "the words of eternal life," and that you are "the Holy One of God."
With his answer to Jesus, Saint Peter actually shows us quite a bit about the nature of faith, for clearly he is aware that Jesus' offer of eternal life has been discounted by the crowd. And he surely knows there is no proof to the contrary. But he's saying that based on what he and the other 11 have seen of Jesus, they are choosing to believe. He's showing the truth that believing in Jesus is always a matter of choice. Peter is kin to a great many Christians down through the centuries who have acknowledged to themselves, if not to others, that there are enough reasons not to believe in Jesus if that is what they conclude, but there are also reasons to believe. And they have made the believing choice.