"(We believe) in one Father, the beginning, and cause of all: begotten of no one: without cause or generation, alone subsisting: creator of all: but Father of one only by nature, His Only-begotten Son and our Lord and God and Saviour Jesus Christ, and Producer of the most Holy Spirit. And in one Son of God, the Only-begotten, our Lord, Jesus Christ: begotten of the Father, before all the ages: Light of Light, true God of true God: begotten, not made, consubstantial with the Father, through Whom all things are made: and when we say He was before all the ages we show that His birth is without time or beginning: for the Son of God was not brought into being out of nothing, He that is the effulgence of the glory, the impress of the Father's subsistence, the living wisdom and power (1 Cor 1:24), the Word possessing interior subsistence, the essential and perfect and living image (Heb 1:3) of the unseen God. But always He was with the Father and in Him, everlastingly and without beginning begotten of Him. For there never was a time when the Father was and the Son was not, but always the Father and always the Son, Who was begotten of Him, existed together. For He could not have received the name Father apart from the Son: for if He were without the Son, He could not be the Father: and if He thereafter had the Son, thereafter He became the Father, not having been the Father prior to this, and He was changed from that which was not the Father and became the Father. This is the worst form of blasphemy. For we may not speak of God as destitute of natural generative power: and generative power means, the power of producing from one's self, that is to say, from one's own proper essence, that which is like in nature to one's self."
~St. John of Damascus: Exposition of the Orthodox Faith, Book 1, Ch. 8