The Roman Catholic participation in the ecumenical movement is based on its ecclesial self-understanding which sees the church as one, recognizing separated sisters and brothers as somehow participating in the reality of Christ’s mystery on earth through their faith and sacramental life. The charter for modern Roman Catholic participation in the ecumenical movement is the decree Unitatis redintegratio of the Second Vatican Council where ecumenism is defined: “The term ‘ecumenical movement’ indicates the initiatives and activities encouraged and organized, according to the various needs of the church and as opportunities offer, to promote Christian unity” (#4). Thus it is the unity of the church which is the primary focus of Roman Catholic participation in the ecumenical movement, while for many of the churches of the Reformation it is collaboration in mission. For the strongly confessional Protestant churches, the Orthodox and Roman Catholics, the doctrinal divisions among believers becomes a primary motivation.

Since the publication of the decree on ecumenism (November 21, 1964) there has been a full development of Roman Catholic ecumenical work. Yet the process of reception of the decree on ecumenism and the subsequent leadership of the Roman Catholic Church in the ecumenical movement only gradually penetrates the life and spirituality of Roman Catholic Christians. The Extraordinary Synod (November, 1985) reiterated the Roman Catholic commitment to take its proper place in the modern ecumenical movement. Following his four predecessors, Pope John Paul II has continually reinforced the priority of placing the ecumenical movement at the very center of modern Roman Catholic identity. The theology on which the Roman Catholic principles of ecumenism are based is the “real, but imperfect communion” which joins Catholics to all who confess Jesus Christ as Lord and Savior according to the scriptures and share a common baptism.

In the decree on ecumenism and subsequent Roman Catholic developments there are three very clear elements to which the Catholic Church is committed in the ecumenical movement: spiritual renewal, theological dialogue towards restoration of full communion, and common mission and witness in the world.

The commitment to internal renewal takes two forms. The first is the theological, liturgical and biblical renewal which makes the evangelical reality of the church to shine through the contemporary Roman Catholic communion. The decree on the liturgy of the Second Vatican Council, returning to the common patristic sources shared with the Orthodox on the one hand, and receiving the insights of the biblical witness of worship in the Reformation churches on the other, urges the fullness of the gospel to be manifested in Catholic liturgical life. Such elements of renewal as the Rite of Christian Initiation for Adults, a more nuanced approach to the rites of reconciliation, and a eucharistic liturgy more in harmony with the great tradition of the church are all elements which bring us closer to the separated brothers and sisters in non-Catholic communions. The decree on revelation, Dei verbum, renews Roman Catholic commitment to the primacy of scripture, within the context of the church’s tradition. It makes clear that the word of God is the center of Christian faith and worship. The decree on the Church and the Modern World, (Gaudium et spes), and the decree on Religious Liberty, (Dignitatis humanae), renew the Roman Catholic understanding of the relationship of church and society, and thus enhancing opportunities for ecumenical cooperation with both Orthodox and Reformation churches in the areas of social ethics and mission to the world.

The second element of renewal which is essential to the ecumenical movement is an enrichment of the theological, spiritual, historical, and prayer life of the diversity of traditions embodied in our still divided churches and ecclesial communities. Key in this personal spiritual renewal is the Week of Prayer for Christian Unity, founded by the Graymoor Friars. This kind of regular common worship and prayer with other Christians enriches personal and parish development. An essential element in this spiritual renewal is the renewal of the educational life of the church in order to help all Roman Catholic Christians place the ecumenical movement at the very center of their identity. The Directory Concerning Ecumenical Matters: Part II, Ecumenism in Higher Education (1969) points out some general principles in this element of the spiritual renewal of the church.

The second major element in Roman Catholic understanding of the ecumenical movement is theological dialogue toward restoration of full communion. The principle underlying these dialogues is that reunion is effected not by compromise but by common biblical and historical study to find a ground of truth which transcends the historic division, by the power of the Spirit working in the ecumenical movement. Roman Catholics take full responsibility for the errors of their forebears in history, and take up the task of dialogue to overcome the theological barriers.

The Catholic Church has been engaged in the Faith and Order dialogue of the World Council of Churches since 1963 and since 1968 has been a full member of that Commission. Specific bilateral dialogues were begun soon after Vatican II, with hopes of restoring full communion. These dialogues with Lutheran, Methodist, Presbyterian/Reformed, Eastern Orthodox, Oriental Orthodox, Disciples of Christ and Anglican theologians have been most fruitful. The Anglican-Roman Catholic International Commission Final Report (1981) is the most well known. The Eastern Orthodox dialogue has been very slow to begin, but remains an important commitment of the Catholic Church. A common declaration with the Oriental Orthodox patriarch of Antioch has opened the way to limited eucharistic sharing, the first such step taken by the Catholic Church in its commitment toward restoring full communion with these churches. In addition to the dialogues leading towards full union, there are other dialogues which involve building a common base of understanding and trying to alleviate historic prejudices. The Baptist, Pentecostal, and Evangelical Dialogues on Mission with the Roman Catholic Church are most notable among these.

The Vatican Secretariat for Promoting Christian Unity, founded in 1960 by Pope John XXIII, oversees these dialogues on a worldwide level. In the United States seven national dialogues are overseen by the bishops’ Committee on Ecumenical and Interreligious Affairs of the National Conference of Catholic Bishops.

The third major Catholic commitment to the ecumenical movement is through common mission and witness, with local initiatives in parishes for social service, evangelism, peace and justice at the very center of Roman Catholic developments. The Vatican has issued a statement on Ecumenical Collaboration at the Regional, National and Local Levels (1975) to support these collaborative ventures. At the present time, the Roman Catholic Church is a member of twenty-seven national councils of churches around the world. In the United States, with the exception of five states with heavy Catholic populations, dioceses are members of half of the state councils or conferences of churches. The Vatican Secretariat and the World Council of Churches have a Joint Working Group that has been working since the Second Vatican Council to enhance their relationship. This Joint Working Group points to the fact that the Roman Catholic Church is as involved with the World Council, though not a formal member, as are some member churches. This relationship has been reinforced by the visits of both Pope Paul VI and Pope John Paul II to the World Council Headquarters in Geneva, Switzerland and their encouraging words about the work of the WCC.

In addition to the 1969 directory, there is a first part of the Directory Concerning Ecumenical Matters (1967) which governs Roman Catholic participation in the ecumenical movement. With the publication of the new Code of Canon Law (1983), and the inclusion in it of Catholic ecumenical priorities, the emphasis on the Bishops’ role in fostering ecumenism, and guidelines for eucharistic sharing, a need was seen for a new directory of ecumenism for the church. The revision of the directory is in progress and should be completed in light of the new code, by 1990.

--Source: Komonchak, J. A., Collins, M., & Lane, D. A. (2000). The New dictionary of theology (316–319).