A few more more links explaining the EO doctrines:
Concerning the Dogma of the Trinity
“All the Christian Churches accept this dogma. In other words, they all believe (1) that God is one, and (2) that there are three Persons in God. Who are different from each other, but are the one God.
The Roman Catholic Church, however, has partly broken the dogma of the Trinity by having introduced in the article of the Creed “and in the Holy Spirit… Who proceeded from the Father,” the words “and from the Son,” in Latin Filioque, after the words “from the Father.”
The addition appeared first in Spain, during the seventh century. In the eighth century it penetrated into France, where, however, it was fervently opposed. (John 15:26 “But when the Helper comes, whom I shall send to you from the Father, the Spirit of truth who proceeds from the Father, He will testify of Me).
At the beginning of the ninth century, Charlemagne asked Pope Leo III to confirm this addition, but the Pope refused to do so. Nevertheless, a considerable number of Churches accepted it, influenced by Charlemagne, who reigned over the greater part of Central Europe. The Eastern Church rose up against this innovation, but its voice was not heeded. During the eleventh century the Roman Church, at the request of Emperor Henry I, accepted the addition. Since then it has come to be accepted by all the Western Churches.
In the sixteenth century both the Anglican and the Protestant Churches overlooked this addition and the former kept both the Creed and the addition after is separation from the Roman Church.
The Anglican Church as well as the Roman tried to prove the justice of this addition, and to this end there were two means: namely, either the Son was given the importance of a secondary cause in the Holy Trinity, or else separate passages from the writings of the Fathers of the Church were quoted, which seemingly confirmed the perfect accord between this addition and the teachings of the tradition.
The Eastern Orthodox Church had no difficulty in proving that no part of the Holy Trinity can be of secondary importance, and that the characteristic of being the cause is the personal characteristic of the Father exclusively and could not be ascribed to the Son without the personal qualities of the Father also being ascribed to Him in some degree, and, therefore, without the dogma of the Trinity being broken. The East quoted in confirmation of the addition are either an entire invention, or distorted and incomplete; and that the quotations which are exact with the authentic sayings of the Fathers of the Church refer to the sending of the Holy Spirit, and not by any means to His procession before all time.
http://www.serfes.org/orthodox/theorthodoxteachings.htm
"Of the Holy Ghost, we both say that He is from the Father, and call Him the Spirit of the Father; while we nowise say that He is from the Son, but only call Him the Spirit of the Son.”
-St John Damascus
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About the Holy Spirit
In the Old Testament we find Yahweh, the one Lord and God, acting toward the world through His Word and His Spirit. In the New Testament the “Word becomes flesh” (Jn 1:14). As Jesus of Nazareth, the only-begotten Son of God becomes man. And the Holy Spirit, who is in Jesus making him the Christ, is poured forth from God upon all flesh (Acts 2:17).
THE HOLY SPIRIT is one of the Persons of the Holy Trinity and is one in essence with the Father. Orthodox Christians repeatedly confess, "And I believe in the Holy Spirit, the Lord, the Giver of life, Who proceeds from the Father, Who together with the Father and the Son is worshiped and glorified..." He is called the "promise of the Father" (Acts 1:4), given by Christ as a gift to the Church, to empower the Church for service to God (Acts 1:8), to place God's love in our hearts (Romans 5:5), and to impart spiritual gifts (I Corinthians 12:7-13) and virtues (Galatians 5:22, 23) for Christian life and witness. Orthodox Christians believe the biblical promise that the Holy Spirit is given through chrismation (anointing) at baptism (Acts 2:38). We are to grow in our experience of the Holy Spirit for the rest of our lives.
http://www.protomartyr.org/believe.html
http://oca.org/orthodoxy/the-orthodo...th/holy-spirit The Symbol of Faith