Ecclesiology is the theology of the Orthodox Christian faith concerning the Church.

Church

The Church is the Body of Christ, a theanthropic (divine-human) communion of Jesus Christ with his people. The sole head of the Church is Christ. The Church is an object of faith, that is, Orthodox Christians believe in the Church. The traditional belief in the Church is attested to in the Nicene-Constantinopolitan Creed as the one, holy, catholic and apostolic Church. By this phrase is meant that the Church is undivided and not many (one), sanctified and set apart for the work of God (holy), whole and characterized by fullness and universality (catholic), and has at its essence the going out into all the world to preach the Gospel and baptize the nations (apostolic).

Because the Church is the Body of Christ, it is also the temple and dwelling place of the Holy Spirit. It is a continued Pentecost.

The Church is the Bride of Christ, the eschatological spouse of the Son of God, united to him in faith and love, for which he gave himself up on the cross. The intimacy of a husband and wife is an earthly image of the intimacy that Christ has with his Church, and the union of an earthly marriage is a shadow of the union of that marriage of the Lamb of God with the Church.

The Orthodox see the Church as a mystical organism, not an organization of like thinking people. In the Church is the community where man is what he is created to be and can grow for eternity in divine life in communion with God through Christ in the Holy Spirit. The unity of the Church is not broken by time or space and is not limited merely to those alive upon the earth. The unity of the Church is the unity of the Blessed Trinity and of all of those who live with God: the holy angels, the righteous dead, and those who live upon the earth according to the commandments of Christ and the power of the Holy Spirit.

The community of the Church is the locus of salvation for mankind; it is truly the Ark in which mankind may be saved from the flood of corruption and sin. In it, Christians sacramentally work out their salvation with fear and trembling (Phil. 2:12), worshipping the Holy Trinity in spirit and in truth. The Church is the pillar and ground of truth (I Tim. 3:15) and thus may be relied upon in the Christian's struggle to apprehend the one truth for himself. The Church is eternal, and the gates of Hell will never prevail against it (Matt. 16:18).

Unity in diversity

The Church as a whole is an icon of God the Trinity, the mystery of unity in diversity. In the Trinity the three are one God, yet each is fully personal; in the Church a multitude of human persons are united in one, yet each preserves his personal diversity unimpaired. The mutual indwelling of the persons of the Trinity is paralleled by the coinherence of the members of the Church. In the Church there is no conflict between freedom and authority; in the Church there is unity, but no totalitarianism.

Membership

The Church consists of the prophets and saints of both the Old and New Covenants, the angels and the concrete, historical community of believers in this earthly life, past and future generations, in one and the same grace of God . It is both visible and invisible, both divine and human. It is visible, for it is composed of concrete congregations, worshipping here on earth; it is invisible, for it also includes the saints and the angels. It is human, for its earthly members are sinners; it is divine, for it is the Body of Christ. Not unlike the incarnation.

There is no separation between the visible and the invisible, between (to use western terminology) the Church militant and the Church triumphant, for the two make up a single and continuous reality. The Church visible, or upon earth, lives in, complete communion and unity with the whole body of the Church, of which Christ is the Head. Orthodoxy, therefore, while using the phrase 'the Church visible and invisible,' strongly insists that there are not two Churches, but one. (The term is only in relation to man.)

The boundaries of the Church are ultimately known only to God himself, but outside the historical context of the Church—that is, the Orthodox Church—the nature of the connection of any human being to the Church (whether a believer in Christ or not) is unknown to us. Throughout Church History, various groups have broken from the Church, a tragic reality which does not divide the Church but rather divides believers from the Church. The final status of Christians in such communities is dependent on God's mercy and grace, as is the case with those with membership in the Church in this life.

Before Pentecost

It is sometimes inaccurate to think that the Church started on Pentecost. The teaching of the holy Fathers is that the Church existed before all other things.

Saint Epiphanius of Cyprus writes, "The Catholic Church, which exists from the ages, is revealed most clearly in the incarnate advent of Christ".

Saint John Damascene observes, "The Holy Catholic Church of God, therefore, is the assembly of the holy Fathers, Patriarchs, Prophets, Apostles, Evangelists, and Martyrs who have been from the very beginning, to whom were added all the nations who believed with one accord".

According to Saint Gregory the Theologian, "The Prophets established the Church, the Apostles conjoined it, and the Evangelists set it in order".

The Church existed from the creation of the Angels, for the Angels came into existence before the creation of the world, and they have always been members of the Church. Saint Clement , Bishop of Rome, says in his second epistle to the Corinthians, the Church "was created before the sun and moon"; and a little further on, "The Church exists not now for the first time, but has been from the beginning".

Pentecost was the ordination of the Apostles, the commencement of the apostolic preaching to the nations, and the inauguration of the priesthood of the new Israel. The feast of holy Pentecost, therefore, determined the beginning of the priesthood of grace, not the beginning of the Church.