What is the difference between the Persons of the Holy Trinity?
God the Father is neither begotten nor does he proceed from any other Person: he is the cause, source, and principle. This is called the Monarchy of the Father. St Gregory the Theologian writes:
The Father is Father, and is unoriginate, because He is from no one; the Son is Son, and is not unoriginate, because He is from the Father. But if you take the word “origin” in a temporal sense, He too is without beginning, for He is the Maker of time and is not subject to time. The Holy Spirit is truly Spirit, coming forth from the Father indeed, but not after the manner of the Son, not by generation but by procession. (St Gregory the Theologian, Orations 39.12)
The Word, or Son of God, is from all eternity begotten of the Father. The Holy Spirit from all eternity proceeds from the Father.
The Orthodox faith is that the Holy Spirit proceeds from the Father, not from the Father and the Son (filioque; see the Study on the Filioque under the Eighth Article). As regards the missions of the Holy Spirit in the world, however, we believe that the Spirit is sent by the Son from the Father, according to the Lord’s teaching: “When the Counselor has come, whom I will send to you from the Father, the Spirit of truth who proceeds from the Father, he will bear witness to me” (Joh 15:26; see Q241, Q243).
The Monarchy of the Father is not a matter of order only. It means that the ground of all that exists is a Person who is free, and not an impersonal essence or a necessity. The Father begets the Son and brings forth the Spirit by nature, and not by a decision of the will, yet not by compulsion either, for in God nature and freedom are not opposed (St John of Damascus, Exact Exposition of the Orthodox Faith, I.8). Because God is Father before he is anything else that we may name, all being has its origin in a Person, and in love; and because the Father is never without the Son and the Spirit, to be God is to be in communion. This is why the doctrine of the Holy Trinity governs what this catechism says of man, who is made in that image (Q113, Q114, and the Study on Person, Nature, and Communion).
