In Peter's person, mission and ministry, in his presence and death in Rome attested by the most ancient literary and archaeological tradition - the Church sees a deeper reality essentially related to her own mystery of communion and salvation: "Ubi Petrus, ibi ergo Ecclesia".12 From the beginning and with increasing clarity, the Church has understood that, just as there is a succession of the Apostles in the ministry of Bishops, so too the ministry of unity entrusted to Peter belongs to the permanent structure of Christ's Church and that this succession is established in the see of his martyrdom.
4. On the basis of the New Testament witness, the Catholic Church teaches, as a doctrine of faith, that the Bishop of Rome is the Successor of Peter in his primatial service in the universal Church;13 this succession explains the preeminence of the Church of Rome,14enriched also by the preaching and martyrdom of St Paul.
In the divine plan for the primacy as "the office that was given individually by the Lord to Peter, the first of the Apostles, and to be handed on to his successors",15 we already see the purpose of the Petrine charism, i.e., "the unity of faith and communion" 16 of all believers. The Roman Pontiff, as the Successor of Peter, is "the perpetual and visible principle and foundation of unity both of the Bishops and of the multitude of the faithful" 17 and therefore he has a specific ministerial grace for serving that unity of faith and communion which is necessary for the Church to fulfil her saving mission. 18
12. St Ambrose of Milan, Enarr. in Ps., 40, 30: PL 14, 1134.
13. Cf. for example St Siricius I, Let. Directa ad decessorem, 10 February 385: Denz-Hun, n. 181; Second Council of Lyons, Professio fidei of Michael Palaeologus, 6 July 1274: Denz-Hun, n. 861; Clement VI, Let. Super quibusdam, 29 November 1351: Denz-Hun, n. 1053; Council of Florence, Bull Laetentur caeli, 6 July 1439: Denz-Hun, n. 1307; Pius IX, Encyc. Let. Qui pluribus, 9 November 1846: Denz-Hun, n. 2781; First Vatican Council, Dogm. Const. Pastor aeternus, Chap. 2: Denz-Hun, nn. 3056-3058; Second Vatican Council, Dogm. Const. Lumen gentium, Chap. 111, nn. 21-23; Catechism of the Catholic Church, n. 882; etc.
14. Cf. St Ignatius of Antioch, Epist. ad Romanos, Introd.: SChr 10, 106-107; St Irenaeus of Lyons, Adversus Haereses, III, 3, 2: SChr 211, 32-33.
15. Second Vatican Council, Dogm. Const. Lumen gentium, n. 20.
16. First Vatican Council, Dogm. Const. Pastor aeternus, Prologue: Denz-Hun, n. 3051. Cf. St Leo I the Great, Tract. in Natale eiusdem, IV, 2: CCL 138, p. 19.
17. Second Vatican Council, Dogm. Const. Lumen gentium, n. 23. Cf. First Vatican Council, Dogm. Const. Pastor aeternus, Prologue: Denz-Hun, n. 3051; John Paul II, Encyc. Let. Ut unum sint, n. 88. Cf. Pius IX, Letter of the Holy Office to the Bishops of England, 16 November 1864: Denz-Hun, n. 2888; Leo XIII, Encyc. Let. Satis cognitum, 29 June 1896: Denz-Hun, nn. 3305-3310.
18. Cf. Jn 17:21-23; Second Vatican Council, Decr. Unitatis redintegratio, n. 1; Paul VI, Apost. Exhort. Evangelii nuntiandi, 8 December 1975, n. 77: AAS 68 (1976) 69; John Paul Il, Encyc. Let. Ut unum sint, n. 98.