ONE CHURCH - The Church is one because God is one, and because Christ and the Holy Spirit are one. There can only be one Church and not many. And this one Church, because its unity depends on God, Christ, and the Spirit, may never be broken. Thus, according to Orthodox doctrine, the Church is indivisible; men may be in it or out of it, but they may not divide it.
According to Orthodox teaching, the unity of the Church is man’s free unity in the truth and love of God. Such unity is not brought about or established by any human authority or juridical power, but by God alone. To the extent that men are in the truth and love of God, they are members of His Church.
Orthodox Christians believe that in the historical Orthodox Church there exists the full possibility of participating totally in the Church of God, and that only sins and false human choices (heresies) put men outside of this unity. In non-Orthodox Christian groups the Orthodox claim that there are certain formal obstacles, varying in different groups, which, if accepted and followed by men, will prevent their perfect unity with God and will thus destroy the genuine unity of the Church (e.g., the papacy in the Roman Church).
Within the unity of the Church 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.