For His Only-begotten Son might, ye Arians, be called 'Father' by His Father, yet not in the sense in which you in your error might perhaps understand it, but (while Son of the Father that begat Him) 'Father of the coming age' (Isa. ix. 6, LXX). For it is necessary not to leave any of your surmises open to you. Well then, He says by the prophet, 'A Son is born and given to us, whose government is upon his shoulder, and his name shall be called Angel of Great Counsel, mighty God, Ruler, Father of the coming age (Isa. ix. 6). The Only-begotten Son of God, then, is at once Father of the coming age, and mighty God, and Ruler. And it is shewn clearly that all things whatsoever the Father hath are His, and that as the Father gives life, the Son likewise is able to quicken whom He will. For 'the dead,' He says, shall hear the voice of the Son, and shall live' (cf. John v. 25), and the will and desire of Father and Son is one, since their nature also is one and indivisible. And the Arians torture themselves to no purpose, from not understanding the saying of our Saviour, 'All things whatsoever the Father hath are Mine.' For from this passage at once the delusion of Sabellius can be upset, and it will expose the folly of our modern Jews. ("On Luke X. 22." 5. As found in Nicene and Post-Nicene Fathers. Series 2. Vol. 204.)
This enables us to see, brethren, that they of Nicaea breathe the spirit of Scripture, in that God says in Exodus, "I am that I am" [Ex. 3:14]; and through Jeremiah, "Who is in his substance and has seen his word" [Jer. 23:18, LXX]; and just below, "if they had stood in my subsistence and heard my words" [Jer. 23:22, LXX]. Now subsistence is essence, and means nothing else but very being, which Jeremiah calls existence in the words, "and they heard not the voice of existence" [Jer. 9:10, LXX]. For subsistence, and essence, is existence: for it is, or in other words exists. This Paul also perceiving wrote to the Hebrews, "who being the brightness of his glory, and the express image of his subsistence." (Synodal Letter to the Bishops of Africa 4)
If "through him all things were made" [Jn. 1:3], and he too is a creature, he would be the creator of himself! And how can what is being created create? Or he that is creating be created? (Synodal Letter to the Bishops of Africa 4)
But the bishops [at the Council of Nicea] ... expressed the sense of the words "of God" more plainly by writing that the Son is of the essence [or "substance"] of God, so that whereas the Creatures, since they do not exist of themselves without a cause, but have a beginning of their existence, are said to be "of God" [as well], the Son alone might be deemed proper to the essence of the Father. For this is peculiar to one who is only-begotten and true Word in relation to a Father, and this was the reason why the words "of the substance" were adopted [in the Nicene Creed]. (Synodal Letter to the Bishops of Africa 5)
If ... [Arians] are asked, "how is [the Son] like [the Father]?," they brazenly reply, "By perfect virtue and harmony, by having the same will with the Father, by not willing what the Father does not will." But let them understand that one assimilated to God by virtue and will is liable also to the purpose of changing, but the Word is not thus ... These characteristics belong to us, who are originate [i.e., had a beginning] and of a created nature. For we, too, ... by progress in virture imitate God, the Lord grating us this grace in the words, "Be merciful, even as your Father is merciful" "Be perfect as your heavenly Father is perfect" [Luke 6:36; Matt. 5:48]. But that originate things are changeable, no one can deny, seeing that angels transgressed, Adam disobeyed, and all stand in need of the grace of the Word. But a mutable things cannot be like God who is truly unchangeable any more than what is created can be like its Creator. That is why, with regard to us, the holy man said, "Lord, who shall be compared to you," and, "Who among the gods is like you, Lord" [Ps. 83:1, LXX; Ps. 86:8]. (Synodal Letter to the Bishops of Africa 7)
But what is that which is proper to and identical with the substance of God, and an Offspring from it by nature, if not by this very fact consubstantial with him that begat it? For this is the distinctive relation of a Son to a Father, and he who denies this does not hold that the Word is Son in nature and in truth. ... But if even after such proofs and after the the testimony of the ancient bishops and the signature of their own father they pretend, as if in ignorance, to be alarmed at the phrase "consubstantial" [a reference to homoousios in the Nicene Creed], then let them say and hold, in simpler terms and truly, that the Son is Son by nature and anathematize, as the synod enjoined, those who say that the Son of God is a creature or a thing made, or of nothing, or that there was a time when he was not, and that he is mutable and liable to change and of another subsistence. And so let them escape the Arian heresy. And we are confident that in sincerely anathematizing those views, they ipso facto confess that the Son is of the Father's substance and consubstantial with him. (Synodal Letter to the Bishops of Africa 8-9)
No Christian can have a doubtful mind on the point that our faith is not in the creature, but in one God, Father Almighty, Maker of all things visible and invisible; and in one Lord, Jesus Christ, his only-begotten Son, and in one Holy Spirit; one God, known in the holy and perfect Trinity, baptized into which, and in it united to deity, we believe that we have also inherited the kingdom of the heavens, in Christ Jesus our Lord. (Synodal Letter to the Bishops of Africa 11)
Because of the oneness of the Word with the Father, they will not have the Son belong to things originated, but rightly regard him as Creator of things that are made. Why then do they say that the Holy Spirit is a creature, who has the same oneness with the Son as the Son with the Father ? Why have they not understood that, just as by not dividing the Son from the Father they ensure that God is one, so by dividing the Spirit from the Word they no longer ensure that the Godhead in the Triad is one, for they tear it asunder, and mix with it a nature foreign to it and of a different kind, and put it on a level with the creatures? On this showing, once again the Triad is no longer one but is compounded of two differing natures ; for the Spirit, as they have imagined, is essentially different. What doctrine of God is this, which compounds him out of creator and creature? Either he is not a Triad, but a dyad, ' with the creature left over. Or, if he be Triad — as indeed he is ! — then how do they class the Spirit who belongs to the Triad with the creatures which come after the Triad ? For this, once more, is to divide and dissolve the Triad. (Letter to Serapion I:2)
Tell us, then, is there any passage in the divine Scripture where the Holy Spirit is found simply referred to as 'spirit' without the addition of 'of God', or 'of the Father', or 'my', or 'of Christ' himself, and 'of the Son', or 'from me' (that is, from God), or with the article so that he is called not simply 'spirit' but 'the Spirit', or the very term 'Holy Spirit' or 'Paraclete' or 'of Truth' (that is, of the Son who says, 'I am the Truth'),— that, just because you heard the word 'spirit', you take it to be the Holy Spirit? ... To sum up, unless the article is present or the above-mentioned addition, it cannot refer to the Holy Spirit. (Letter to Serapion I:4)
Trinity Quotes from Christian History
Quotes from the Early Church Fathers: on the Trinity - Apostles Creed