Two senses of the word Son, 1. adoptive; 2. essential; attempts of Ariansto find a third meaning between these; e.g. that our Lord only was created immediately by God (Asterius's view), or that our Lord alone partakes the Father. The second and true sense; God begets as He makes, really; though His creation and generation are not like man's; His generation independent of time; generation implies an internal, and therefore an eternal, act in God; explanation of Proverbs 8:22
6 They say then what the others held and dared to maintain before them; “Not always Father, not always Son; for the Son was not before His generation, but, as others, came to be from nothing; and in consequence God was not always Father of the Son; but, when the Son came to be and was created, then was God called His Father. For the Word is a creature and a work, and foreign and unlike the Father in essence; and the Son is neither by nature the Father's true Word, nor His only and true Wisdom; but being a creature and one of the works, He is improperly called Word and Wisdom; for by the Word which is in God was He made, as were all things. Wherefore the Son is not true God.”
Now it may serve to make them understand what they are saying, to ask them first this, what in fact a son is, and of what is that name significant. In truth, Divine Scripture acquaints us with a double sense of this word:— one which Moses sets before us in the Law, 'When you shall hearken to the voice of the Lord your God, to keep all His commandments which I command you this day, to do that which is right in the eyes of the Lord your God, you are children of the Lord your God;' as also in the Gospel, John says, 'But as many as received Him, to them gave He power to become the sons of God:'— and the other sense, that in which Isaac is son of Abraham, and Jacob of Isaac, and the Patriarchs of Jacob. Now in which of these two senses do they understand the Son of God that they relate such fables as the foregoing? For I feel sure they will issue in the same irreligion with Eusebius and his fellows.
If in the first, which belongs to those who gain the name by grace from moral improvement, and receive power to become sons of God (for this is what their predecessors said), then He would seem to differ from us in nothing; no, nor would He be Only-begotten, as having obtained the title of Son as others from His virtue. For granting what they say, that, whereas His qualifications were fore-known, He therefore received grace from the first, the name, and the glory of the name, from His very first beginning, still there will be no difference between Him and those who receive the name after their actions, so long as this is the ground on which He as others has the character of son. For Adam too, though he received grace from the first, and upon his creation was at once placed in paradise, differed in no respect either from Enoch, who was translated there after some time from his birth on his pleasing God, or from the Apostle, who likewise was caught up to Paradise after his actions; nay, not from him who once was a thief, who on the ground of his confession, received a promise that he should be immediately in paradise.
7. When thus pressed, they will perhaps make an answer which has brought them into trouble many times already; “We consider that the Son has this prerogative over others, and therefore is called Only-begotten, because He alone was brought to be by God alone, and all other things were created by God through the Son.” Now I wonder who it was that suggested to you so futile and novel an idea as that the Father alone wrought with His own hand the Son alone, and that all other things were brought to be by the Son as by an under-worker. If for the toil's sake God was content with making the Son only, instead of making all things at once, this is an irreligious thought, especially in those who know the words of Esaias, 'The everlasting God, the Lord, the Creator of the ends of the earth, hungers not, neither is weary; there is no searching of His understanding.' Rather it is He who gives strength to the hungry, and through His Word refreshes the labouring. Again, it is irreligious to suppose that He disdained, as if a humble task, to form the creatures Himself which came after the Son; for there is no pride in that God, who goes down with Jacob into Egypt, and for Abraham's sake corrects Abimelek because of Sara, and speaks face to face with Moses, himself a man, and descends upon Mount Sinai, and by His secret grace fights for the people against Amalek. However, you are false even in this assertion, for 'He made us, and not we ourselves. ' He it is who through His Word made all things small and great, and we may not divide the creation, and says this is the Father's, and this the Son's, but they are of one God, who uses His proper Word as a Hand, and in Him does all things. This God Himself shows us, when He says, 'All these things has My Hand made;' while Paul taught us as he had learned, that 'There is one God, from whom all things; and one Lord Jesus Christ, through whom all things.' Thus He, always as now, speaks to the sun and it rises, and commands the clouds and it rains upon one place; and where it does not rain, it is dried up. And He bids the earth yield her fruits, and fashions Jeremias in the womb. But if He now does all this, assuredly at the beginning also He did not disdain to make all things Himself through the Word; for these are but parts of the whole.
8. But let us suppose that the other creatures could not endure to be wrought by the absolute Hand of the Unoriginate and therefore the Son alone was brought into being by the Father alone, and other things by the Son as an underworker and assistant, for this is what Asterius the sacrificer has written, and Arius has transcribed and bequeathed to his own friends, and from that time they use this form of words, broken reed as it is, being ignorant, the bewildered men, how brittle it is. For if it was impossible for things originate to bear the hand of God, and you hold the Son to be one of their number, how was He too equal to this formation by God alone? And if a Mediator became necessary that things originate might come to be, and you hold the Son to be originated, then must there have been some medium before Him, for His creation; and that Mediator himself again being a creature, it follows that he too needed another Mediator for his own constitution. And though we were to devise another, we must first devise his Mediator, so that we shall never come to an end. And thus a Mediator being ever in request, never will the creation be constituted, because nothing originate, as you say, can bear the absolute hand of the Unoriginate. And if, on your perceiving the extravagance of this, you begin to say that the Son, though a creature, was made capable of being made by the Unoriginate, then it follows that other things also, though originated, are capable of being wrought immediately by the Unoriginate; for the Son too is but a creature in your judgment, as all of them. And accordingly the origination of the Word is superfluous, according to your irreligious and futile imagination, God being sufficient for the immediate formation of all things, and all things originate being capable of sustaining His absolute hand.
These irreligious men then having so little mind amid their madness, let us see whether this particular sophism be not even more irrational than the others. Adam was created alone by God alone through the Word; yet no one would say that Adam had any prerogative over other men, or was different from those who came after him, granting that he alone was made and fashioned by God alone, and we all spring from Adam, and consist according to succession of the race, so long as he was fashioned from the earth as others, and at first not being, afterwards came to be.
Source: De Decretis (New Advent)