Aeterna Dei Sapientia §42

⁴² St. Leo, therefore, maintained that the Bishop of Rome, as Peter's successor and Christ's Vicar on earth, is the focal center of the entire visible unity of the Catholic Church. And St. Leo's opinion is clearly supported by the evidence of the Gospels and by ancient Catholic tradition, as these words show: "Out of the whole world one man is chosen, Peter. He is set before all the elect of every nation, before all the apostles and all the Fathers of the Church; so that although there are among God's people many priests and many pastors, Peter governs by personal commission all whom Christ rules by His supreme authority. Great and wonderful, beloved, is the share in its own power which the Divine Condescension assigned to this man. And if it desired other princes to share anything in common with him, never except through him did it accord what it did not deny to others." (37)