Ancient source used: Athanasius, Defense of the Nicene Definition 33
(1.) Beloved, since rumors usually travel faster than accurate information, you have probably learned from other sources what happened concerning the church’s faith at the Great Council assembled at Nicaea. As we do not want the facts to be misrepresented by such reports, we have been obliged to transmit to you, first, the formula of faith which we ourselves [i.e. Eusebius] presented, and next, the second, which the assembled fathers put forth with some additions to our words. (2.) Our own letter, which was read in the presence of our most pious Emperor and declared to be good and free from objectionable statements, reads as follows:
(3.) “We report now to you our faith, which we have received from the bishops who preceded us when we were first instructed and received the washing [of baptism], which we have also come to know from the divine Scriptures; as we believed and taught in the priesthood, and in the episcopate itself, and as we also believe at the present time:
(4.) “We believe in one God, the Father Almighty, the Maker of all things visible and invisible. And in one Lord Jesus Christ, the Word of God, God from God, Light from Light, Life from Life, Only-begotten Son, first-born of every creature, begotten from the Father before all the ages, by whom also all things were made; who for our salvation was made flesh, and lived among men, and suffered, and rose again the third day, and ascended to the Father, and will come again in glory to judge the living and the dead. And we believe also in one Holy Spirit. (5.) We believe each of these to be and to exist, the Father truly Father, and the Son truly Son, and the Holy Spirit truly Holy Spirit, as also our Lord said when he sent forth his disciples to preach, “Go teach all nations, baptizing them in the name of the Father and of the Son, and of the Holy Spirit.” Concerning which things we confidently affirm that this is what we maintain, how we think, and what we have held up until now, and that we will maintain this faith unto death, anathematizing every ungodly heresy. (6.) We testify that we have ever thought these things from our hearts and souls, from earliest memory, and now think and confess the truth before God Almighty and our Lord Jesus Christ. We are able to provide evidence that will assure you that even in times past we have believed and preached the same.”
(7.) There was nothing to contradict in this statement of faith we put forward. In fact our most pious Emperor, before any one else, testified that it was comprised of most orthodox statements. He even confessed that such were his own sentiments, and he advised all present to agree to it, and to subscribe and agree with its articles, with the insertion of the single word, “of the same being as” (homoousios). He gave his interpretation of this word, saying that “<the Son> was not “of the same being as” according to what we experience in our bodies, as if the Son had come to be by dividing or breaking off from the Father. For his nature could not be subjected to any bodily experiences, as it does not consist of matter, exists in a spiritual realm, has no body. Therefore such things must be thought of in divine, unspeakable concepts.” Such were the theological remarks of our most wise and most pious Emperor; but they were intent on adding the word “of the same being as” and drew up the following statement:
(8.) [The Faith pronounced in the Council].
“We believe in one God, the Father Almighty, Maker of all things visible and invisible: and in one Lord Jesus Christ, the Son of God, begotten of the Father, Only-begotten, that is, from the essence of the Father; God from God, Light from Light, true God from true God, begotten not made, of the same being as the Father, by whom all things were made, both things in heaven and things on earth; who for us men and for our salvation came down and was made flesh, was made man, suffered, and rose again the third day, ascended into heaven, and will come to judge the living and the dead; and we believe in the Holy Spirit. But those who say, ‘Once he did not exist,’ and ‘He did not exist before he was begotten,’ and ‘He came to be from nothing,’ or those who pretend that the Son of God is ‘of another subsistence (hypostasis) or being (ousia),’ or ‘created’(ktistos), or ‘alterable’ (treptos), or ‘changeable’ (alloiōtos), the catholic church anathematizes.”
(9.) As this formula was being debated, we made sure to inquire in what sense they introduced “from the essence of the Father,” and “of the same being as the Father.” Through intense questioning and explaining, the meaning of the words was examined closely. They explained that the phrase “of the same being as” indicated that the Son is truly from the Father, but he is not a part of him. (10.) We felt we could agree to this word when used in this sense, to teach, as it did, that the Son was from the Father, not however a part of his essence. On this account we agreed to the sense ourselves, without denying even the term “of the same being as,” since maintaining peace was our goal, provided we did not depart from the orthodox understanding.
(11.) In the same way we also accepted the phrase “begotten, not made,” since the council asserted that “made” (poiētos) was a term used to designate other creatures which came to be through the Son, to whom the Son had no similarity. So according to their reasoning, he was not something made that resembled the things which came to exist through him, but was of an essence which is too high to be put on the same level as anything which was made. The divine sayings teach us that his essence was begotten from the Father, and that the mode of his being begotten is inexpressible and unable to be conceived by any nature which has had a beginning of its existence.
(12.) So when we considered it, we found that there are grounds for saying that the Son is “of the same being as” the Father; not like human bodies, nor like mortal beings, for he is not “of the same being as” by dividing his essence, or by cutting something off, or by having something done to him, or being altered, or by changing the Father’s essence and power (since the Father’s nature has no beginning to its existence, and therefore none of those descriptions apply to it). (13.) “Of the same being as the Father” suggests that the Son of God bears no resemblance to the creatures who came into being, but that he is in every way similar to his Father alone who begat him, and that he is not of any other subsistence (hypostasis) and essence (ousia), but from the Father. It also seemed good for us to agree to this term, since we were aware that even among the ancients, some learned and eminent bishops and writers have used the term “of the same being as,” in their theological teaching concerning the Father and Son.
(14.) So much then for the creed which was composed at the council, to which all of us agreed, not without some questioning, but according to a specific sense, brought up before the most pious Emperor himself, and qualified by the considerations mentioned above. (15.) As far as the condemnation they attached to the end of the creed, it did not cause us pain, because it forbad the use of words not found in Scripture, from which almost all the confusion and disorder in the Church have come. Since then no divinely inspired Scripture has used the phrases, “out of nothing,” and “once he was not,” and the rest which follow, there appeared no ground for using or teaching them. We think that this was a good decision, since it has never been our custom to use these terms.
(16.) Additionally, it did not seem out of place to condemn the statement “Before he was begotten he did not exist,” because everyone confesses that the Son of God existed before he was begotten according to the flesh. At this point in the discussion, our most pious Emperor maintained that the Son existed before all ages even according to his divinely inspired begetting, since even before the act of begetting was performed, in potentiality he was with the Father, even before he was begotten by him, since the Father is always Father, just as he is always King and always Savior; he has the potentiality to be all things, and remains exactly the same forever.
(17.) We had to pass this on to you, beloved, to make sure our deliberation, our questions, and our ultimate agreement, was clear to you. You see how reasonably we resisted even to the last minute as long as we were offended at statements which differed from our own. But when a candid examination of the sense of the words was conducted, we accepted without contention what no longer pained us, since they appeared to us to be in harmony with what we ourselves have professed in the faith which we have already declared.
Translation from Athanasius (NPNF, vol. 4, pp. 74-6), adapted by AJW