What is an ecumenical council? (Glad you asked: Q&A on church teaching).

Forty years ago this month, on Oct. 11, 1962, Pope John XXIII opened the first session of the Second Vatican Council. He had given the council a threefold agenda: (1) the better internal ordering of the church itself; (2) unity among Christians; and (3) the promotion of peace throughout the world. The council met for four sessions of roughly 10 weeks between 1962 and 1965. Pope John died after the first session, so the others were presided over by Pope Paul VI.

It is hard to overestimate the enormous impact Vatican II has had on the life of the church. The council encouraged sweeping reforms in the official liturgy of the Catholic Church; it redefined its relationship with other churches; it showed a greater openness and invited dialogue with non-Christian religious traditions; it demanded the church work for peace and social justice in the world; and, internally, it called for an understanding of the church not as only a juridical institution but as a pilgrim church of the People of God bound in communion.

Vatican II was the latest in a long history of "ecumenical councils." An ecumenical council is the gathering of all the bishops of the world as opposed to regional or local gatherings. According to current church law, only the pope can call such a council, and he alone sets its agenda. Acts of the council are only binding when approved by the pope and the body of bishops and officially proclaimed by papal authority.

Roman Catholics traditionally consider there to have been 21 such councils. However, the only councils accepted as truly ecumenical by both the churches of the East and the West are the first seven. The first four councils (Nicaea, Constantinople I, Ephesus, and Chalcedon) are recognized as normative for all churches that confess the Nicene and Apostles' creeds, and the decrees of those four councils form the basis for ecumenical dialogues.

When looked at more closely, the Catholic list of 21 councils seems somewhat problematic: Some of the medieval reforming councils represented only issues for the Western Church so that they may be more properly called (as Pope Paul VI did) "general councils of the West." Even the "modern" councils--Trent in the 16th century, Vatican I in the 19th, and Vatican II in the 20th--dealt mainly with Roman Catholic concerns.

Ecumenical councils have been convoked over history for quite different reasons, either to face pressing heresies or to foster reform in the church. Vatican II was called with an explicit desire to be a pastoral council both for the sake of the church and to serve the needs of the larger world within which the church lives. Vatican II was the only ecumenical council in the history of the church that did not issue any condemnations of heresies or errors. It was the only council that actually addressed some of its documents to those outside the church ("persons of good will"), and it was the only council in history that directly spoke to the issue of ecumenism, reconciliation, and dialogue not only among Christians but among all the world's great religious traditions.

The late theologian Karl Rahner argued that Vatican II marked the beginning of what he called the "world church." Rahner meant that the old notion of Christianity as the religion of Europe or of European inspiration has now given way to an understanding of the church as being represented by the worlds of Africa, Asia, and the Americas. Vatican II asked us to open our eyes to a bigger and more complex world. The great future task of the church is to try to understand how the Christian message can be framed to speak to those cultures.

By its openness to the world, Vatican II may have initiated that new era, but it may require a future council to understand fully how a world church is to look and what shape it may be required to take. Less than 40 years after its closing session we are still trying to implement the vision of Vatican II, and until that vision is realized, it may be too premature to think of a new council in the early years of this new millennium.

LAWRENCE S. CUNNINGHAM, the John A. O'Brien professor of theology at the University of Notre Dame.