Originally published at National Catholic Register
Few subjects aroused the attention of the Council Fathers at Vatican II more than the effort to restore unity among Christians, a task known by the term “ecumenism.”
The Council’s concern for this topic was present throughout its work, especially in its reflection on the Church, and would be the specific theme of the Decree Unitatis Redintegratio. The Council approved this text on Nov. 21, 1964, on the same solemn occasion as the promulgation of the dogmatic constitution on the Church, Lumen Gentium, as well as the decree on the Catholic Churches of the Eastern Rite, Orientalium Ecclesiarum.
The concern for unity among Christians, present from the very origins of the Church, took on particular force in the early 20th century in what has come to be known as the Ecumenical Movement.
From the initial announcement of the Second Vatican Council in January 1959, Pope St. John XXIII had wanted the assembly to be a renewed invitation to unity for the faithful of separated Christian communities. This sentiment would resonate deeply among the Council Fathers, as well as more broadly in the Church and the world as a whole.
By the start of the Council, in October
