"Cathedra" literally means the established seat of the bishop, located in the mother church of a diocese, which for this reason is called "cathedral," and it is the symbol of the authority of the bishop and, in particular, of his "magisterium," that is, of the evangelical teaching that he, insofar as a successor of the apostles, is called to guard and transmit to the Christian community.
When the bishop takes possession of the local Church that is entrusted to him, he, bearing the miter and the shepherd's crosier, sits on the cathedra. From that seat he will guide, as teacher and shepherd, the journey of the faithful in faith, hope and charity.
Which was, then, the "cathedra" if St. Peter? He, chosen by Christ as "rock" on which to build the Church (cf. Matthew 16:18), began his ministry in Jerusalem, after the ascension of the Lord and Pentecost. The first "seat" of the Church was the Cenacle, and in all probability in that room, where Mary, the Mother of Jesus, also prayed with the disciples, a special place was reserved for Simon Peter.
Subsequently, the see of Peter was Antioch, a city situated on the Oronte River in Syria, today Turkey, which at the time was the third metropolis of the Roman Empire after Rome and Alexandria in Egypt. Of that city, evangelized by Barnabas and Paul, where "for the first time the disciples were called Christians" (Acts 11:26), Peter was the first Bishop.
In fact, the Roman Martyrology, before the reform of the calendar, established also a specific celebration of the Chair of Peter at Antioch. From there, Providence led Peter to Rome, where he concluded with martyrdom his course of service to the Gospel. For this reason, the See of Rome, which had received the greatest honor, received also the task entrusted by Christ to Peter of being at the service of all the local Churches for the building and unity of the whole People of God.
In this way the See of Rome came to be known as that of the Successor of Peter, and the "cathedra" of its Bishop represented that of the apostle charged by Christ to feed all his flock. It is attested by the most ancient Fathers of the Church, as for example St. Irenaeus, bishop of Lyon, who in his treatise "Against Heresies" describes the Church of Rome as "greatest and most ancient, known by all; … founded and constituted at Rome by the two glorious Apostles Peter and Paul"; and he adds: "With this Church, because of her outstanding superiority, the universal Church must be in agreement, that is, the faithful everywhere" (III, 3, 2-3).
Tertullian, for his part, affirms: "How blessed this Church of Rome is! The Apostles themselves shed on her, with their blood, the whole of the doctrine" ("La Prescrizione degli Eretici," 36). The Chair of the Bishop of Rome represents, therefore, not only his service to the Roman community, but also his mission of guide of the whole People of God.
To celebrate the "Chair" of Peter, as we do today, means, therefore, to attribute to it a strong spiritual significance and to recognize in it a privileged sign of the love of God, good and eternal Shepherd, who wants to gather the whole of his Church and guide her along the way of salvation.
Among so many testimonies of the Fathers, I would like to refer to that of St. Jerome, taken from a letter of his to the Bishop of Rome, particularly interesting because he makes explicit reference in fact to the "chair" of Peter, presenting it as the safe harbor of truth and peace. Jerome writes thus: "I decided to consult the chair of Peter, where that faith is found exalted by the lips of an Apostle; I now come to ask for nourishment for my soul there, where once you received the garment of Christ. I follow no leader save Christ, so I enter into communion with your beatitude, that is, with the chair of Peter for this I know is the rock upon which the Church is built! ("Le Lettere," I, 15,1-2).
Dear Brothers and Sisters, in the apse of St. Peter's Basilica, as you know, is found the monument to the Chair of the Apostle, a mature work of Bernini, made in the shape of a great bronze throne, supported by the statues of four Doctors of the Church, two from the West, St. Augustine and St. Ambrose, and two from the East, St. John Chrysostom and St. Athanasius.
I invite you to pause before that evocative work, which today it is possible to admire decorated with so many candles, and pray in a particular way for the ministry that God has entrusted to me. Raising one's gaze to the alabaster glass window that opens precisely above the chair, invoke the Holy Spirit, so that he will always sustain with his light and strength my daily service to the whole Church.