The opening prayer in the Orthodox prayer book is directed to the Holy Spirit, who is described as the "Paraclete" and the "Spirit of Truth," while the creed speaks of "the Giver of Life." What is the Holy Spirit? He is the third person of the Holy Trinity, one person of the same essence with the other two persons of the one Christian God. The Orthodox Church has been characterized as a pneumatological church, because she lays such great emphasis upon the work of the Holy Spirit. She describes the whole purpose of the Christian life on earth as the acquisition of the Holy Spirit. A saint has put it in the following terms: "Prayer, fasting, vigils, and all other Christian practices, however good they may be in themselves, certainly do not constitute the aim of our Christian life: they are but the indispensable means of attaining that aim. For the true aim of the Christian life is acquisition of the Holy Spirit of God." Fasts, vigils, charities, and other good works done in the name of Christ are the means of acquiring the Holy Spirit of God. The prayer life of the faithful starts with the invocation of the Holy Spirit. Every morning the Orthodox place themselves under the protection of the Holy Spirit when they recite the beautiful prayer: "O Heavenly King, comforter, the Spirit of truth, who art everywhere and fillest all things, the treasury of blessings and giver of life, come and abide in us. Cleanse us from all impurity, and of your goodness save our souls."
But why so much emphasis on the Holy Spirit? Because the Holy Spirit is the Spirit of God, the life-giving power of God, the promulgator of Christ's work in the salvation and eternal destiny of man. Jesus Christ promised His apostles that "the Holy Spirit, whom the Father will send in my name, he will teach you all things, and bring to your remembrance all that I have said to you" (Jn. 14:2G).
The Holy Spirit continues the work of Jesus through inspired human beings. He carries on the redemption and sanctification of man. He reveals and preaches the good tidings through people, through prophets, the Fathers, and the saints of the Church. The Holy Spirit speaks to man's heart and transforms him into a new creation, through repentance and Christ's teachings.
The Holy Spirit's power leads the human person to achieve the final aim of the Christian life, the theosis, or deification, of human nature, a notion very dear to the Orthodox. Theosis means life in God, the transformation of a human being into a little god within God. This notion is in perfect agreement with the Scriptures. Once people picked up stones to cast at Christ. When Jesus asked why they were doing this, the people answered that it was because He was insulting God by calling himself God. And Jesus answered: "It is not written in your law, 'I said, you are gods?" (Jn. 10.34; Ps. 82.6). Thus Jesus himself calls man a little god. This teaching has been taken over by the Fathers and the tradition of the Church. It constitutes an important element of the eschatological teachings of the Greek Orthodox Church.
Saint Basil the Great describes man as a creature who has received the order to become a god; and Saint Athanasios, as is well known, has expressed it in the classic words "God became man that man might become god." And the Church in the hymn for Holy Thursday Matins sings as follows: "In my kingdom, said Christ, I shall be God with you as gods" (cf. Ps. 82.6: Jn. 10.34).
The great theological quests of the fourth and fifth centuries ultimately resulted in the affirmation that salvation is the divinisation of humanity and its eternal presence in God, the source of its life. Damnation is exactly the opposite, the deprivation of God's presence in the life of humanity. The deification of the human has its beginnings here on earth, but it will reach its fulfilment in the life to come. It is the result of man's response to the Holy Spirit in man's life.
The Holy Spirit works in human beings in various ways, especially through the sacraments of the Church and through reading and listening to the Holy Scriptures. Christ promised that the Holy Spirit would teach the Church all things necessary for man's salvation. To the end of time the Holy Spirit will be leading the faithful and the Church into deeper and deeper understanding of the truth of God.
The Holy Spirit guides the Church, or the community, in understanding the meaning of Jesus' teachings, which would not otherwise be possible. Upon the departure of Christ from the earth, the Holy Spirit came to inspire, guide, and establish the Ekklesia and to remain with it forever. "I will not leave you desolate," Jesus promised His disciples (Jn. 14:18). In this respect Jesus proved different from other great teachers. Plato writes that, when Sokrates died, his disciples "thought that [they] would have to spend the rest of their lives orphans, as children bereft of a father, and [they) did not know what to do about it." The Paraclete took Jesus' place and remains forever with the disciples. It is the Spirit, then, who gives purpose in life and who remains with the Church forever as "the Lord, the Giver of Life."
SOURCE : Demetrios Constantelos, Understanding the Greek Orthodox Church, Hellenic College Press, Brookline, Massachusetts 1998.