"Chair" is a symbol of authority. The Feast of Saint Peter's Chair is a celebration of the authority which Jesus gave to Peter as the head of the Church on earth. In our human lives we celebrate many aspects of a person's life: we remember birthdays, wedding anniversaries, the anniversary of the death of someone dear to us and so on. So we should not be surprised that, in faith, we celebrate many aspects of saints' lives. In the life of Peter, the two greatest graces which he received from Jesus the Lord were his pontifical authority and his martyrdom, and so we celebrate these.

In celebrating Peter's pontifical authority, of course, we are celebrating this great grace: namely that the Lord, who is our eternal shepherd, never leaves his flock untended, as we say in the Preface for the Masses of Apostles. It is, then, fitting that the first reading from the First Letter of Peter speaks of a shepherd's care for his flock. The responsorial Psalm reminds that, ultimately, the Lord is our Shepherd: he exercises his care for the universal Church through the Petrine ministry of the Pope.