This is a topic of continuing reflection and debate, especially given rapid globalization. The Faith and Order Commission of the World Council of Churches is currently seeking the responses of its member churches to the document, The Nature and Purpose of the Church. Section (I. A. i.) reads:

9. The Church belongs to God. It is the creation of God's Word and Holy Spirit. It cannot exist by and for itself. 10. The Church is centered and grounded in the Gospel, the Word of God. The Church is the communion of those who live in a personal relationship with God who speaks to them and calls forth their trustful response - the communion of the faithful. Thus the Church is the creature of God's Word which as a living voice creates and nourishes it throughout the ages. This divine Word is borne witness to and makes itself heard through the scriptures. Incarnate in Jesus Christ, it is testified to by the Church and proclaimed in preaching, in sacraments, and in service.
(See: F&O # 181: www.wcc-coe.org/wcc/what/faith/nature1.html.

1) Various Definitions: Theologians like Augustine and Aquinas have left us with a tradition of debate over the identity of the church. One author (Brown) speaks of churches that reflect the different heritages of the Apostles. For Orthodox, this is the Church of the seven councils (Ware). From the perspective of what the church does, one might speak of different models of the church (Dulles). One compelling model is that of mystical communion, raising questions about the boundaries of the church. Rahner’s proposal is that if the church’s identity includes openness, then a certain amount of “vicariousness” means that the church thinks and feels on her own behalf and on behalf of others (Vatican II, Decree on Ecumenism, Unitatis Redintegratio, nr. 11). This is the third of three types of the church identified by Van Beeck, “pistic,” “charismatic, ” and “mystic” as centered in a Spirit-enlivened Jesus. But the struggle today is with unity, often defined as that of a common magisterium located in Rome (F. A. Sullivan), raising the question of how the Church of Christ is maintained in the truth of the Gospel through the Holy Spirit. At this point many issues pertain. Luther, fearful of a theology of glory that ended in self-exaltation, suggested instead a theology of the cross, often yielding an unstable reality. This, for Barth, is the church as herald, or an assembly that responds to God’s word (Küng).

2) Consider the Following Example: Taking as a point of departure the term “communio sanctorum,” we might fill this out with a sense of Jesus as the expected “prophet,” “priest,” and “king” long sought in messianic Judaism. Eusebius of Caesarea, Erasmus, and the company of the Reformed developed this christological theme. It has been drawn into ecclesiology as an aspect of ecumenical thinking (Y. Congar, G. H. Williams, etc.). Christians, the mystical body of Christ (Rom 8:17, 12:4; I Cor. 6:19; and II Cor. 2:5), might find their vocation under the rubric of the threefold office (triplex munus) of Christ. Heightened in times of crisis, they – and the church – play a prophetic role as truth-tellers and justice-seekers; find a priestly role in prayer and forgiveness and, in their [servant]-king role they regard one another as images of divine royalty, or God. But note how “forgiveness” defines the church: There is no worship apart from forgiveness (Matt. 5:23-24). Forgiveness defines the material identity of the church (John 20: 21-23). Forgiveness, as it tends toward reconciliation, defines (II Cor 5:19) vocation.

3) Examples of Recent Literature Include:
• Karl Barth, Dogmatics in Outline (New York: Harper Torchbooks, 1959).
• Dietrich Bonhoeffer, The Communion of the Saints (New York: Harper & Row, 1963).
• Raymond Brown, The Churches the Apostles Left Behind (New York: Paulist Press, 1984)
• Avery Dulles, Models of the Church (New York: Doubleday/Image Books, 1978)
• Hans Küng, The Church (New York: Sheed & Ward, 1968).
• Karl Rahner, Foundations of Christian Faith – An Introduction… (NY: Crossroad, 1978).
• Francis A. Sullivan, SJ, Magisterium. Teachng Authority in the Catholic Church (NY: Paulist, 1983)
• Frans Josef van Beeck, SJ, Catholic Identity After Vatican II… (Chicago: Loyola, 1985).
• Timothy (Kallistos) Ware, The Orthodox Church (London: Penguin Books, 1963).