A rock can serve two purposes: it can provide a foundation for the ground we walk on, or it can cause us to stumble. We can stand on a rock and feel secure or if we walk without expecting it we can trip over it.
In Matthew 16:13-23 Jesus names Peter as the rock upon which He will build His Church. He does so because Peter correctly understands Jesus is the Messiah. Peter and the truth of the Messiah he proclaims will become foundational to the very Church that God will build; a Church so strong the gates of the netherworld will have no power of it.
On the other hand, Peter is still human and has a lot to learn about the true nature of the Messiah. His humanness comes out when he fails to understand the humanness of Jesus and how the Messiah he believes in will have to suffer and die. Just after demonstrating profound spiritual wisdom, Peter begins to rely on his own understanding rather than God when he hears something that does not correspond to what he understood the role of the Messiah to be. As Jesus says, Peter begins to think not as God does but as human beings do.
Peter could become a stumbling block for others if he does not continue to lean on God for understanding as he goes out to proclaim this truth of the Messiah to the world.
In this time we are living through there is a lot of debate about what God has to say over this or that issue we are facing. We too can be tempted to take particular sides on these various issues based on our own understanding of God’s will without first stopping to discern what God’s understanding may actually be. In our own effort to discern God’s will in the midst of all the complexities of our modern day world, we too can become stumbling blocks for others if we lean on our own understanding rather than God’s. We too can fall into the risk of only seeing the problems of our day as humans do and not as God does; we too can become a stumbling block to truth and unity within the Church.
As Peter learns in this Gospel, continual recognition of our own humanness and need for God is necessary to allow us to remain open to the voice of the Spirit as the Spirit continues to reveal the truth of God and help us apply it to our own times.
Humility is the virtue that enables this.
“Grasp the truth of God by using the way He Himself provides, since He sees the weakness of our footsteps. That way consists first, of humility, second, of humility, and third, of humility. Unless humility precede, accompany, and follow up all the good we accomplish, unless we keep our eyes fixed on it, pride will snatch everything right out of our hands.”Saint Augustine (Letter 118, 22)
Saint Augustine offered this advice after years of his own searching for truth in the midst of the complexities of his own time. As Augustine reveals in his Confessions, pride often hindered his own ability to discover God in the midst of his own search for truth among the many voices of his own time. We must continue to listen to the voice of the Spirit so that we can discover moments of grace to see as God does, not as human beings do.
Today is the feast of Saint John Vianney who was known for his extraordinary grace in the confessional, spending twelve to seventeen hours a day hearing confessions. He possessed great spiritual wisdom. As Bert Ghezzi says, “A few minutes in his confessional was enough to turn hardened sinners into saints.” People said he could read their consciences, see their past sins, and predict the future. Despite the fact that he had little education before entering the seminary and even in seminary had a difficult time passing exams, he possessed great spiritual wisdom.
I believe Saint Augustine and Saint John Vianney provides a witness to the power of humility.
 Bert Ghezzi, Voices of the Saints: A 365-Day Journey with Our Spiritual Companions (Chicago: Loyola Press, 2000), 634-635.