Catechism of the Catholic Church

813 The Church is one because of her source: "the highest exemplar and source of this mystery is the unity, in the Trinity of Persons, of one God, the Father and the Son in the Holy Spirit." ²⁵⁹ The Church is one because of her founder: for "the Word made flesh, the prince of peace, reconciled all men to God by the cross, . . . restoring the unity of all in one people and one body." ²⁶⁰ The Church is one because of her "soul": "It is the Holy Spirit, dwelling in those who believe and pervading and ruling over the entire Church, who brings about that wonderful communion of the faithful and joins them together so intimately in Christ that he is the principle of the Church's unity." ²⁶¹ Unity is of the essence of the Church:

What an astonishing mystery! There is one Father of the universe, one Logos of the universe, and also one Holy Spirit, everywhere one and the same; there is also one virgin become mother, and I should like to call her "Church." ²⁶²

814 From the beginning, this one Church has been marked by a great diversity which comes from both the variety of God's gifts and the diversity of those who receive them. Within the unity of the People of God, a multiplicity of peoples and cultures is gathered together. Among the Church's members, there are different gifts, offices, conditions, and ways of life. "Holding a rightful place in the communion of the Church there are also particular Churches that retain their own traditions." ²⁶³ The great richness of such diversity is not opposed to the Church's unity. Yet sin and the burden of its consequences constantly threaten the gift of unity. And so the Apostle has to exhort Christians to "maintain the unity of the Spirit in the bond of peace." ²⁶⁴

815 What are these bonds of unity? Above all, charity "binds everything together in perfect harmony." ²⁶⁵ But the unity of the pilgrim Church is also assured by visible bonds of communion:

- profession of one faith received from the Apostles;

-common celebration of divine worship, especially of the sacraments;

- apostolic succession through the sacrament of Holy Orders, maintaining the fraternal concord of God's family. ²⁶⁶

816 "The sole Church of Christ [is that] which our Savior, after his Resurrection, entrusted to Peter's pastoral care, commissioning him and the other apostles to extend and rule it.... This Church, constituted and organized as a society in the present world, subsists in (subsistit in) in) the Catholic Church, which is governed by the successor of Peter and by the bishops in communion with him." ²⁶⁷

The Second Vatican Council's Decree on Ecumenism explains: "For it is through Christ's Catholic Church alone, which is the universal help toward salvation, that the fullness of the means of salvation can be obtained. It was to the apostolic college alone, of which Peter is the head, that we believe that our Lord entrusted all the blessings of the New Covenant, in order to establish on earth the one Body of Christ into which all those should be fully incorporated who belong in any way to the People of God." ²⁶⁸