Unitatis redintegratio (Latin for "Restoration of unity") is the Second Vatican Council's decree on ecumenism. It was passed by a vote of 2,137 to 11 of the bishops assembled at the Council, and was promulgated by Pope Paul VI on 21 November 1964.
The title of the document is taken from the opening words of the Latin text. The opening words of the official English translation are: "The restoration of unity among all Christians is one of the principal concerns of the Second Vatican Council."
Unitatis Redintegratio calls for the reunion of Christendom and is similar to a previous call for unity by Pope Leo XIII in the 1894 encyclical Praeclara gratulationis publicae. However, Unitatis articulates a different kind of ecclesiology from Praeclara. It focuses on the unity of the people of God and on separated Christian brethren rather than insisting according to the classical formulation that schismatics must return to the fold under the unity of the Vicar of Christ.
Unitatis acknowledges that there are serious problems facing prospects of reunion with Reformation communities that make no attempt to claim apostolic succession as the Anglican communion does. Ecclesial communities which adhere to Calvinism are a particularly challenging case because they and Catholicism have important doctrinal differences on key issues such as ecclesiology, liturgy and mariology. Other communities have insoluble doctrinal differences with Catholic Christianity because their theology of the Holy Trinity is manifestly incompatible with the doctrine as articulated by the council of Nicea in the early Church.
The numbers given correspond to the section numbers within the text.
"...it remains true that all who have been justified by faith in Baptism are members of Christ's body, and have a right to be called Christian, and so are correctly accepted as brothers by the children of the Catholic Church.
Traditionalist Catholics argue that this document contradicts the teachings of popes who preceded the Second Vatican Council and gives a false representation of the unity of the Catholic Church. They cite documents such as Mortalium Animos (1928) by Pope Pius XI, which addresses statements similarly expressed in Unitatis Redintegratio. Pius XI considered the position that the Church of Christ can be divided into sections and that the Unity of the Church has not been achieved as a false opinion. Considering these notions, Pius wrote "[T]he Apostolic See cannot on any terms take part in [non-Catholic] assemblies, nor is it anyway lawful for Catholics either to support or to work for such enterprises; for if they do so they will be giving countenance to a false Christianity, quite alien to the one Church of Christ. Shall We suffer, what would indeed be iniquitous, the truth, and a truth divinely revealed, to be made a subject for compromise? For here there is question of defending revealed truth."
Cardinal Walter Kasper discussed the status of the problems by the document on the 40th anniversary of the promulgation of Unitatis in remarks entitled "The Decree on Ecumenism - Read Anew After Forty Years".