There are enough quotes here to form a good picture of the early Christian explanation of the relationship between the Father and the Son. Without some time spent on the subject, though, that is difficult because their doctrine of the Trinity was slightly different from our western view (though very close to the typical Eastern Orthodox view). I have written several pages making the early church doctrine of the Trinity as easy to understand as possible, and I believe those are worth reading to put these quotes in context.
I do have to be honest, though, if you are able to form a solid theological explanation of the Holy Spirit from these quotes, you are doing better than me! Not much is explained about the Holy Spirit in either the quotes of the early Christians nor in Scripture. Both at times seem to equate the Spirit with our Lord Jesus, and both seem to clearly differentiate them at other times.
Later addition: George Bull, in his Defensio fidei Nicaenae ("Defense of the Faith of Nicea"), explains that the Son is occasionally referred to as the Spirit because as the Son of God he is Spirit like the Father. An example of referring to the Lord as the Spirit is 2 Corinthians 3:17, which says, "The Lord is the Spirit, and where the Spirit of the Lord is, [there is] liberty." In Bull's book, he quotes a line from Hermas saying, "And the Son is the Holy Spirit," but that line is questionable, found in only the Latin manuscript of the Greek work.
I have tried to include references to the Spirit below, but I am not about to try to interpret them. As George Bull puts it, "It is most certain that the Son of God, the second Peson of the Godhead, is in the writings of the Fathers throughout called by the title of 'Spirit,' 'Spirit of God,' and 'Holy Spirit.' If there be any one so much a stranger to the works of the ancients as not to know this, he may consult the author I just quoted [Hugo Grotius, d. 1645]."
Ignatius of Antioch, AD 110
Our God, Jesus Christ, was, according to the appointment of God, conceived in the womb by Mary, of the seed of David, but by the Holy Spirit. (Letter to the Ephesians 18)
Ignatius … to the church of God the Most High Father and his beloved Son, Jesus Christ, … I glorify God, even Jesus Christ, who has given you such wisdom … (Letter to the Smyrneans intro-ch. 1)
Anonymous, Letter to Diognetus, AD 80 - 130
This is he who was from the beginning, who appeared as if new, and was found old, and yet who is ever born afresh in the hearts of the saints. This is he who, being from everlasting, is today called the Son. (Letter to Diognetus 11)
Justin Martyr, c. AD 150
"No one knows the Father but the Son, nor the Son but the Father, and those to whom the Son will reveal him" [Matt. 21:27]. The Jews, accordingly, being are throughout of the opinion that it was the Father of the universe who spoke to Moses [in the burning bush], though the One who spoke to him was the Son of God. … They are justly charged, both by the Spirit of Prophecy and by Christ himself, with knowing neither the Father nor the Son. Those who affirm that the Son is the Father are proven neither to be acquainted with the Father nor to know that the Father has a Son. The Son, being the first-begotten Word of God, is God. Of old he appeared in the shape of and in the likeness of an angel to Moses and other prophets, but now in the time of your reign [i.e., during the Roman empire] … he became man by a virgin … for the salvation of those who believe in him. (First Apology 63).
There is then brought to the president of the brethren [I think this refers to whoever is presiding at a meeting, but no one knows for certain] bread and a cup of wine mixed with water. He takes them, gives praise and glory to the Father of the universe through the name of the Son and of the Holy Spirit, and offers thanks at considerable length for our being counted worthy to receive these things at his hands. (First Apology 65)
Leningrad Codex of the Hebrew Scriptures
For all things with which we are supplied, we bless the Maker of all through his Son Jesus Christ and through the Holy Spirit. (First Apology 67)
But to the Father of all, who is unbegotten, there is no name given. .. And His Son, who alone is properly called Son, the Word who also was with him and was begotten before the works, when at first He created and arranged all things by Him, is called Christ, in reference to His being anointed and Godís ordering all things through him. (Second Apology 6)
Our Saviour Jesus Christ … being the Word of God, inseparable from Him in power, having assumed [the form of] man, who had been made in the image and likeness of God, restored to us the knowledge of the religion of our ancient forefathers. (Hortatory Address to the Greeks 38)
Permit me first to recount the prophecies, which I wish to do in order to prove that Christ is called both God and Lord of hosts and Jacob in parable by the Holy Spirit. (Dialogue with Trypho 36)
[Trypho the Jew speaking to Justin about Christians in general] Trypho said, " … You utter many blasphemies. You're attempting to persuade us that this crucified man was with Moses and Aaron, spoke to them in the pillar of the cloud, became crucified, ascended up to heaven, will come again to earth, and ought to be worshiped!"
Then I answered, "I know that, as the word of God says, this great wisdom of God, the Maker of all things, and the Almighty, is hidden from you." (Dialogue with Trypho 38)
In the fourty-fourth Psalm [LXX, in our Masoretic text, it's the 45th], these words are … referred to Christ: "My heart has brought forth a good Word" [v. 1, considered by the early Christians to be a reference to the birth of the Son/Word in eternity past]. (Dialogue with Trypho 38)
Since we find it recorded in the memoirs of the apostles that he is the Son of God, and since we call him the Son, we have understood that he proceeded before all creatures from the Father by his power and his will ... and that he became man by the virgin, in order that the disobedience which proceeded from the serpent might receive its destruction in the same way in which it derived its origin. (Dialogue with Trypho 100)
For I have already proved that he was the only-begotten of the Father in everything, being begotten, in a unique way, Logos and Power by him, and afterwards become man through the virgin, as we have learned from the memoirs [of the apostles]. (Dialogue with Trypho 105)
Hermas, AD 100 - 160
"First of all, sir," I said, "Explain to me what is the meaning of the rock and the gate?"
"This rock," he answered, "and this gate are the Son of God."
"How, sir?" I said. "The rock is old, and the gate is new."
"Listen," he said, "and understand, O ignorant man. The Son of God is older than all his creatures, so that he was a fellow counselor with the Father in his work of creation. For this reason he is old."
"And why is the gate new, sir?" I said.
"Because," he answered, "he became manifest in the last days of the dispensation. For this reason the gate was made new, that they who are to be saved by it might enter into the kingdom of God." (Shepherd of Hermas III:9:12)
Tatian, c. AD 165
God was in the beginning, but the beginning, we have been taught, is the power of the Logos. For the Lord of the universe … since no creature was yet in existence, was alone. But, since he is all power, himself the necessary ground of things visible and invisible, with him were all things. With him, by Logos-power, the Logos Himself … subsists. By His simple will the Logos springs forth; and the Logos … becomes the first-begotten work of the Father.
Him we know to be the beginning of the world. But He came into being by participation, not by abscission [cutting off]. For what is cut off is separated from the original substance, but that which comes by participation … does not render him deficient from whom it is taken.
For just as from one torch many fires are lighted, but the light of the first torch is not lessened by the kindling of many torches, so the Logos, coming forth from the Logos-power of the Father, has not divested [the Father] of the Logos-power.
I myself, for instance, talk, and you hear. Yet I certainly do not become destitute of speech by the transmission of speech, but by the utterance of my voice I endeavour to reduce to order the unarranged matter in your minds. And as the Logos, begotten in the beginning, begat in turn our world, having first created for himself the necessary matter, so also I, in imitation of the Logos, being born again, and having become possessed of the truth, am trying to reduce to order the confused matter which is kindred with myself. (Address to the Greeks 5)
Theophilus, AD 168
You will say ... to me: "You said that God cannot to be contained in one place; how do you now say that he walked in Paradise?"
Hear what I say: The God and Father of all truly cannot be contained, and is not found, in a place ... but his Word, through whom he made all things, being his power and his wisdom, assuming the person of the Father and Lord of all, went to the garden in the person of God and conversed with Adam.
For the divine writing itself teaches us that Adam said that he had heard the voice. What else is this voice but the Word of God, who is also his Son? [He is] not [a son] in the way the poets and writers of myths speak of sons of gods begotten from intercourse, but as truth expounds, the Word, who always exists, residing within the heart of God. For before anything came into being [God] had him as a counselor, being his own mind and thought.
But when God wished to make all that he determined, he begot this Word, uttered, the firstborn of all creation, not himself being emptied of the Word [or Reason], but having begotten Reason, and always conversing with his Reason.
And this is what the holy writings teach us, as well as all the Spirit-bearing men, one of whom, John, says, "In the beginning was the Word, and the Word was with God" [Jn. 1:1], showing that at first God was alone, and the Word in him. Then he says, "The Word was God; all things came into existence through him, and apart from him not one thing came into existence."
The Word, then, being God, and being naturally produced from God, then whenever the Father of the universe wills, he sends him anywhere, and he is both heard and seen, being sent by Him, and is found in a place. (To Autolycus II:22)
Hermas, c. AD 170
I wish to explain to you what the Holy Spirit that spoke with you in the form of the Church showed you, for that Spirit is the Son of God. (Shepherd of Hermas. Similitude 9th. Ch. 1.)
Athenagoras, c. AD 177
We acknowledge ... a Son of God. Don't let anyone think it ridiculous that God should have a Son. ... The Son of God is the Logos of the Father ... He is the first product of the Father, not as though he was being brought into existence, for from the beginning God, who is the eternal Mind, had the Logos in himself. (A Plea for the Christians 10)
We acknowledge a God, and a Son, his Logos, and a Holy Spirit, united in essence—the Father, the Son, the Spirit—because the Son is the Intelligence, Reason, and Wisdom of the Father, and the Spirit an effluence, as light from fire. (A Plea for the Christians 24)
Irenaeus, AD 183 - 186
Learn then, foolish men [i.e., the gnostics], that Jesus who suffered for us, and who dwelt among us, is himself the Word of God. … He, the only-begotten Son of the only God, who, according to the good pleasure of the Father, became flesh for the sake of men. (Against Heresies I:9:3)
[The Gospel] according to John relates [Jesus Christ's] original, effectual, and glorious generation from the Father, thus declaring, "In the beginning was the Word, and the Word was with God, and the Word was God" [John 1:1]. (Against Heresies III:11:8)
How is Christ the end of the Law if he is not also the final cause of it? For he who has brought in the end himself also made the beginning. And it is he who says to Moses, "I have surely seen the affliction of my people who are in Egypt, and I have come down to deliver them" [Ex. 3:7-8]. It was customary from the beginning for the Word of God to ascend and descend for the purpose of saving those who were in affliction. (Against Heresies IV:12:4)
Clement of Alexandria, c. AD 190
Though despised as to appearance, [Jesus] was in reality adored, the expiator of sin, the Savior, the clement, the Divine Word; he that is truly most apparently Deity. He is made equal to the Lord of the universe because he was his Son, and the Word was in God. (Exhortation to the Heathen 10)
The Lord is the hierophant [interpreter of sacred mysteries] and seals while illuminating him who is initiated. He presents to the Father him who believes to be kept safe for ever. Such are the reveries of my mysteries. If it is your wish, be also initiated, and you shall join the choir along with angels around the unbegotten and indestructible and the only true God, the Word of God, raising the hymn with us. This Jesus, who is eternal, the one great High Priest of the one God, and of His Father, prays for and exhorts men. (Exhortation to the Heathen 12)
I call on the whole race of men, whose Creator I am, by the will of the Father. Come to Me, that you may be put in your due rank under the one God and the one Word of God … for to you of all mortals I grant the enjoyment of immortality. For I want to … confer on you both the Word and the knowledge of God, my complete self. This am I, this God wills … this [is] the harmony of the Father; this is the Son, this is Christ, this the Word of God, the arm of the Lord, the power of the universe, the will of the Father … I desire to restore you according to the original model, that you may become also like me. (Exhortation to the Heathen 12)
It cannot be said that the Lord is not willing to save humanity because of ignorance, as though he does not know how each on is to be cared for. Ignorance does nat apply to the God who, before the foundation of the world, was the Counselor of the Father. For he was the Wisdom in which the Sovereign God delighted [Prov. 8:30]. The Son is the power of God. He is the Father's most ancient Word before the production of all things and his Wisdom. He is then properly called the Teacher of the beings he formed. Nor does he ever abandon the care of mankind by being distracted by pleasure, not the One who assumed flesh—which by nature is susceptible to suffering—and trained it to such an extent that it could not suffer. (Miscellanies VII:2
We are therefore to love him equally with God. And he loves Christ Jesus who does his will and keeps his commandments. (Who Is the Rich Man Who Shall Be Saved 29)
Tertullian, c. AD 200
We ... believe that there is one only God—but under the following dispensation, or oikonomia [Tertullian quotes the Greek word for "order," "dispensation," or "arrangement" here], as it is called—that this one only God has also a Son, his Word, who proceeded from himself, by whom all things were made and without whom nothing was made. ...
That this rule of faith has come down to us from the beginning of the Gospel ... will be apparent both from the lateness of date which marks all heresies and also from the absolutely novel character of our new-fangled Praxeas. (Against Praxeas 2)
But as for me, who derive the Son from no other source but from the substance of the Father ... how can I possibly be destroying the Monarchy from the faith [i.e., removing the singular rule of God as modalists accused trinitarians of doing], when I preserve it in the Son just as it was committed to him by the Father. (Against Praxeas 4, emphasis mine because of its importance to the Nicene Creed)
Before all things God was alone … He was alone because there was nothing external to him except himself. Yet even then he was not alone,for he had with him that which he possessed in himself, that is to say, his own Reason. [Which is how Tertullian translates the Greek "Logos"] (Against Praxeas 5)
God is rational, and Reason was first in him … This Reason was his own thought, which the Greeks call Logos, by which term we also designate Word [Tertullian is writing in Latin and used the word "Sermo"], and therefore it is now usual with our people, owing to the simple translation of [Logos] to say that the Word was in the beginning with God, even though it would be more suitable to regard Reason as the more ancient. God did not have Word from the beginning, but he had Reason even before the beginning. Word itself consists of Reason, which it thus proves to have been the first to exist as being its own substance. Not that this distinction is of any practical importance.
[Are you looking for a meaning to all that? The basic premise is that the Logos existed in the beginning with God, and Tertullian has some philosophical reasons for wanting to translate that as Reason rather than Word, even though Word is more common] (Against Praxeas 5)
Although God had not sent out his Word, he still had him within himself … as he silently planned and arranged within himself everything which he was afterwards to utter through his Word. (Against Praxeas 5)
Observe, then, that when you are silently conversing with yourself, this very process is carried on within you by your reason, which meets you with a word at every movement of your thought … Whatever you think, there is a word … You must speak it in your mind …
Thus, in a certain sense, the word is a second person within you, through which in thinking you utter speech … The word is itself a different thing from yourself. Now how much more fully is all this transacted in God, whose image and likeness you are? (Against Praxeas 5)
This power and disposition of the Divine Intelligence is also set forth in the Scriptures under the name of Wisdom; for what can be better entitled to the name of Wisdom than the Reason or the Word of God?† Listen therefore to Wisdom herself, constituted in the character of a Second Person: "At the first the Lord created me as the beginning of his ways … " that is to say, he created and generated me in his own intelligence. Then, again, observe the distinction between them implied in the companionship of Wisdom with the Lord [referencing the Father]. "When he prepared the heaven," says Wisdom, "I was present with him." (Against Praxeas 6)
Now, as soon as it pleased God to put forth into their respective substances and forms the things which he had planned and ordered within himself, in conjunction with his Wisdomís Reason and Word, he first put forth the Word himself … in order that all things might be made through him through whom they had been planned and disposed. (Against Praxeas 6)
At that time the Word assumes his own form and glorious garb, his own sound and vocal utterance, when God says, "Let there be light." This is the perfect nativity of the Word, when he proceeds forth from God … "The Lord created me as the beginning of His ways;" then afterward begotten, to carry all into effect: "When he prepared the heaven, I was present with him." In this way he makes him equal to him, for by proceeding from himself he became his first-begotten Son … and His only-begotten also, because alone begotten of God, in a way peculiar to himself, from the womb of his own heart, just as the Father himself testifies: "My heart," says he, "has emitted my most excellent Word." (Against Praxeas 7)
He became the Son of God and was begotten when he proceeded forth from him. … But you [Praxeas, a heretic who held to modalism ("Jesus only")] will not allow him to be really a substantive being, by having a substance of his own in such a way that he may be regarded as an objective thing and a person, and so be able to make two, the Father and the Son, God and the Word.
For you will say, what is a word but a voice and sound of the mouth … but for the rest a sort of void, empty, and incorporeal thing. I, on the contrary, contend that nothing empty and void could have come forth from God … for all things which were made through him, he made. … How could he who is empty have made things which are solid, and he who is void have made things which are full, and he who is incorporeal have made things which have body? … Is that Word of God, then, a void and empty thing, which is called the Son, who is himself designated God? "The Word was with God, and the Word was God" [Jn. 1:1] … This for certain is he "who, being in the form of God, thought it not robbery to be equal with God" [Php. 2:6].
In what form of God? Of course he means in some form, not in none. For who will deny that God is a body even though "God is Spirit" [Jn. 4:24] For Spirit has a bodily substance of its own kind, in its own form. … Whatever, therefore, was the substance of the Word that I designate a Person, I claim for it the name of Son; and while I recognize the Son, I assert his distinction as second to the Father. (Against Praxeas 7)
[Written against modalism or "Jesus only"] If you want me to believe him to be both the Father and the Son, show me some other passage where it is declared, "The Lord said to himself, ‘I am my own Son, today have I begotten myself.’" … On your side, however, you must make Him out to be a liar, an impostor, and a tamperer with his word, if, when he was himself a Son to himself, he assigned the part of his Son to be played by another. All the Scriptures attest the clear existence of—and distinction [of persons] in—the Trinity, and indeed furnish us with our Rule of faith. He who speaks, and he of whom he speaks and to whom he speaks, cannot possibly seem to be one and the same. (Against Praxeas 11)
I shall follow the apostle [Paul], so that if the Father and the Son are alike to be invoked, I shall call the Father "God" and invoke Jesus Christ as "Lord."
But when Christ alone [is invoked], I shall be able to call him "God." As the same apostle says, "Of whom is Christ, who is over all, God blessed forever" [Rom. 9:5].
For I should give the name of "sun" even to a sunbeam, considered by itself. But if I were mentioning the sun from which the ray emanates, I would certainly withdraw the name of sun from the mere beam. For although I do not make two suns, still I shall reckon both the sun and its ray to be as much two things—and two forms of one undivided substance—as God and his Word, as the Father and the Son. (Against Praxeas 13)
"No one has seen God at any time" [1 Jn. 4:12]. What God does he mean? The Word? But he [the Holy Spirit, through the Scriptures] has already said, "Him we have seen and heard, and our hands have handled, the Word of Life" [1 Jn. 1:1-2]. Well, what God does he mean? It is of course the Father, with whom was the Word, the only-begotten Son, who is in the bosom of the Father, and has revealed him himself. ... Moreover, he expressly called Christ God, saying, "Of whom are the fathers, of whom as concerning the flesh Christ came, who is over all, God blessed forever" [Rom. 9:5]. He shows us also that the Son of God, who is the Word of God, is visible, because he who became flesh was called Christ. Of the Father, however, he says to Timothy, "Whom none among men has seen, nor indeed can see," and he accumulates the description in still ampler terms, "Who alone has immortality and dwells in the light that no one can approach" [1 Tim. 6:16]. It was of him, too, that he said in a previous passage, "Now to the King eternal, immortal, invisible, to the only God" [1 Tim. 1:17], so that we might apply the contrary qualities to the Son himself—mortality, accessibility—of whom the apostle testifies that "He died according to the Scriptures" [1 Cor. 15:3]and that "He was seen by himself last of all" [1 Cor. 15:8]. This happened, of course, by means of the light that was accessible, although it was not without imperiling his sight that he experienced that light [Acts 22:11] (Against Praxeas 15)
Origen, c. AD 230
Since many saints participate in the Holy Spirit, he cannot therefore be understood to be a body, which being divided into corporeal parts, is partaken of by each one of the saints. Instead, he is manifestly a sanctifying power, in which all are said to have a share who have deserved to be sanctified by his grace. (De Principiis I:1:3)
The Holy Spirit is an intellectual existence and subsists and exists in a unique manner. (De Principiis I:1:3)
Hoving refuted, then, as well as we could, every notion which might suggest that we were to think of God as in any degree corporeal, we go on to say that, according to strict truth, God is incomprehensible and incapable of being measured. (De Principiis I:1:5)
God, therefore, is not to be thought of as being either a body or as existing in a body, but as an uncompounded intellectual nature. (De Principiis I:1:6)
Whatever … is a porperty of bodies cannot be said of either the Father or the Son, but what belongs to the nature of Deity is common to the Father and the Son. … Because, then, neither seeing nor being seen can be properly applied to an incorporeal and invisible nature, neither is the Father, in the Gospel, said to be seen by the Son nor the Son by the Father, but the One is said to be known by the Other. (De Principiis I:1:8)
By this divine sense, therefore, not of the eyes but of a pure heart, which is the mind, God may be seen by those who are worthy. For you will certainly find in all the Scriptures, both old and new, the term "heart" repeatedly used instead of "mind." (De Principiis I:1:9)
In the first place, we must note that the nature of that deity which is in Christ in respect to his being the only-begotten Son of God is one thing, and that human nature which he assumed in these last times for the purposes of the dispensation is another. (De Principiis I:2:1)
Wisdom as a "She"
Both the Hebrew word for wisdom, chokmah, and the Greek word, sophia, are feminine nouns. That's meaningless to those of us who speak only English; however, in languages that give gender to nouns, writers have no choice but to refer to feminine nouns as "she" and "her."
This does not mean that they are thinking that the noun is actually female. For example, the German tasse means cup. It is feminine, so it appropriate to refer to the coffee cup in your hand as "she," while referring to the masculine coffee in the cup as "he."
It's funny to us English-speakers, but it's perfectly normal in languages with gender applied to nouns.
Therefore it is essential that we not be thrown off when Proverbs refers to Wisdom as "she." That does not necessarily mean that Wisdom is female. Origen here states clearly that the "Son" of God is the Wisdom of Proverbs, yet he refers to Wisdom as "she" nonetheless. That's because this is the proper thing to do in Greek grammar, not because he believes Wisdom or the Son of God is female.
For [the Son] is termed Wisdom according to the expression of Solomon: "The Lord created me the beginning of his ways and among his works before he made any other thing. He founded me before the ages" [Prov. 8:22-23]. … He is also styled Firstborn, as the apostle has declared, " … who is the firstborn of every creature" [Col. 1:15]. The Firstborn, however, is not by nature a different person from the Wisdom, but one and the same. Finally, the apostle Paul says that "Christ is the power of God and the wisdom of God" [1 Cor. 1:24]. Let no one, however, imagine that we mean anything impersonal when we call him the Wisdom of God … If, then, it is once rightly understood that the only-begotten Son of God is his Wisdom existing in substance, I do not know whether our curiosity ought to advance beyond this. (De Principiis I:2:1-2)
Who that is capable of entertaining reverential thoughts or feelings regarding God can suppose or believe that God the Father ever existed, even for a moment of time, without having generated this Wisdom? For in that case we must say either that God was unable to generate Wisdom before he produced her … or that he possessed the power indeed, but—what cannot be said of God without impiety—was unwilling to use it, both of which suppositions, it is obvious to all, are alike absurd and impious … Therefore we have always held that God is the Father of his only-begotten Son, who was born of him in truth and derives from him what he is, but without any beginning. (De Principiis I:2:2)
Since all the creative power of the coming creation was included in the very existence of Wisdom … having been formed beforehand and arranged by the power of foreknowledge—because of these very creatured which had been described (as it were) and prefigured in Wisdom herself, does Wisdom say, in the words of Solomon, that she was created the beginning of the ways of God, inasmuch as she contained within herself either the beginnings, or forms, or species of all creation. (De Principiis I:2:2)
John … says in the beginning of his Gospel, when defining God by a special definition to be the Word, "And God was the Word, and this was in the beginning with God" (Jn. 1:1). Let him, then, who assigns a beginning to the Word or Wisdom of God, take care not to be not guilty of impiety against the unbegotten Father himself, since he denies that he had always been a Father, had generated the Word, and had possessed wisdom in all preceding periods, whether they be called times or ages. (De Principiis I:2:3)
Whatever … we have said of the Wisdom of God will be appropriately applied to and understood of the Son of God because he is the Life, the Word, theTruth, and the Resurrection. For all these titles are derived from his power and operations, and in none of them is there the slightest ground for understanding anything of a corporeal nature which might seem to denote size, from, or color. (De Principiis I:2:4)
It is monstrous and unlawful to compare God the Father, in the generation of his only-begotten Son, … to any man or other living thing engaged in such an act. For we must of necessity hold that there is something exceptional and worthy of God which does not admit of any comparison at all, not merely in things, but which cannot even be conceived by human thought or discovered by perception. Thus, do not imagine that a human mind would be able to comprehend how the unbegotten God is made the Father of the only-begotten Son because his generation is as eternal and everlasting as the brilliancy which is produced from the sun. (De Principiis I:2:4)
For the Son is the Word, and therefore we are not to understand that anything in him is recognizable by the senses. He is Wisdom, and in wisdom there can be no suspicion of anything corporeal. (De Principiis I:2:6)
[The Son] is the true Light which enlightens every man that comes into this world, but he has nothing in common with the light of the sun. Our Savior, therefore, is the image of the invisible God, inasmuch as compared with the Father himself he is the Truth, and as compared with us, to whom he reveals the Father, he is the image by which we come to the knowledge of the Father, whom no one knows save the Son and he to whom the Son is pleased to reveal him. And the method of revealing him is through the understanding, for he by whom the Son himself is understood understands, as a consquence, the Father also, according to his own words, "He that has seen me has seen the Father also" [Jn. 14:9]. (De Principiis I:2:6)
The Son of God, who was in the form of God, divesting himself [of his glory], makes it his object … to demonstrate to us the fullness of his deity. For instance, suppose that there were a statue so enormous that it filled the whole world and which, because of its size, could be seen by no one. [Now suppose] another statue were formed completely resembling it … so that those who were unable to behold the one of enormous proportions should, on seeing the latter, acknowledge that they had seen the former … By some such similitude the Son of God, divesting himself of his equality with the Father and showing us the way to the knowledge of him, is made the express image of his person. (De Principiis I:2:8)
The Son of God, though placed in the very insignificant form of a human body, showed that there was in him an immense and invisible greatness because of the resemblance of h is words and power to the Father. (De Principiis I:2:8)
Let us see now what is the meaning of the expression which is found in the Wisdom of Solomon [an apocryphal book treated as Scripture by only the Orthodox Churches today], where it is said of Wisdom that "it is a kind of breath of the power of God, the purest efflux of the glory of the Almighty, the splendor of the Eternal Light, the spotless mirror of the working or power of God, and the image of his goodness" [Wisdom 7:25-26]. These, then, are the definitions which he gives of God, pointing out by each one of them certain attributes of the Wisdom of God … With all propriety he says that Wisdom is the breath of the power of God … although the breath of all this mighty and immeasurable power … proceed from the power itself, as the will does from the mind, yet even this will of God is nevertheless made to become the power of God. Another power, accordingly, is produced, which exists with properties of its own, a kind of breath, as Scripture says, of the primal and unbegotten power of God, deriving from him its being and never at any time non-existent. For if anyone were to assert that it did not formerly exist, but came into existence afterwards, let him explain the reason why the Father, who gave it being, did not do so before. If he shall grant that there was once a beginning, when that breath proceeded from the power of God, we shall ask him again, why not even before the beginning? … By which it is shown that the breath of God's power always existed, having no beginning save God himself. … And according to the expression of the apostle, that Christ is "the power of God" [1 Cor. 1:24] it ought to be termed not only the breath of the power of God, but power out of power. (De Principiis I:2:9)
Hippolytus, c. AD 225
These things then, brothers, are declared by the Scriptures. And the blessed John, in the testimony of his Gospel, gives us an account of this economy [the "order" or "plan"] and acknowledges this Word as God, when he says, "In the beginning was the Word, and the Word was with God, and the Word was God" [Jn. 1:1]. If, then, the Word was with God, and was also God, what follows? Would one say that he speaks of two Gods? I shall not indeed speak of two Gods, but of one; of two Persons however, and of a third economy, viz., the grace of the Holy Spirit. For the Father indeed is One, but there are two Persons, because there is also the Son; and then there is the third, the Holy Spirit. The Father decrees, the Word executes, and the Son is revealed, through whom the Father is believed on. The economy of harmony is led back to one God; for God is One. It is the Father who commands, and the Son who obeys, and the Holy Spirit who gives understanding: the Father who is above all, and the Son who is through all, and the Holy Spirit who is in all. And we cannot otherwise think of one God, but by believing in truth in Father and Son and Holy Spirit. ... The Father’s Word, therefore, knowing the economy and the will of the Father, to wit, that the Father seeks to be worshipped in none other way than this, gave this charge to the disciples after He rose from the dead: "Go, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Spirit" [Matt. 28:19]. And by this He showed, that whosoever omitted any one of these, failed in glorifying God perfectly. For it is through this Trinity that the Father is glorified. For the Father willed, the Son did, the Spirit manifested. ("Against the Heresy of One Noetus." par. 14. In Ante-Nicene Fathers. Vol. V. American Ed. Edinburgh: T&T Clark, 1885.)
Eusebius, c. AD 325
Whoever then defines the Son as made of things that are not, and as a creature produced from nothing pre-existing, forgets that while he concedes the name of Son, he denies him to be a Son in reality. For he that is made of nothing, cannot truly be the Son of God, any more than the other things which have been made; but the true Son of God, forasmuch as he is begotten of the Father, is properly denominated the only-begotten and beloved of the Father. For this reason also, he himself is God; for what can the offspring of God be, but the perfect resemblance of him who begot him?
A sovereign indeed builds a city, but does not beget it; and is said to beget a son, not to build one. An artisan, also, may be called the framer, but not the father of his work; while he could by no means be styled the framer of him whom he had begotten. So also the God of the Universe is the Father of the Son; but might be fitly termed the Framer and Maker of the world. And although it is once said in Scripture, "The Lord created me the beginning of his ways on account of his works" [Prov. 8:22], yet it becomes us to consider the import of this phrase, which I shall hereafter explain; and not, as Marcellus has done, from a single passage to jeopardize the most important doctrine of the church. (cited in Ecclesiastical History of Socrates Scholasticus II:21)
Athanasius, AD 325 - 370
We believe in one Unbegotten God, Father Almighty, maker of all things both visible and invisible, that hath His being from Himself. And in one Only-begotten Word, Wisdom, Son, begotten of the Father without beginning and eternally ... We believe, likewise, also in the Holy Spirit that searcheth all things, even the deep things of God ... But just as a river, produced from a well, is not separate, and yet there are in fact two visible objects and two names. For neither is the Father the Son, nor the Son the Father. For the Father is Father of the Son, and the Son, Son of the Father. For like as the well is not a river, nor the river a well, but both are one and the same water which is conveyed in a channel from the well to the river, so the Father’s deity passes into the Son without flow and without division. For the Lord says, 'I came out from the Father and am come' (Joh. xvi. 28). But He is ever with the Father, for He is in the bosom of the Father, nor was ever the bosom of the Father void of the deity of the Son. ... But we do not regard God the Creator of all, the Son of God, as a creature, or thing made, or as made out of nothing, for He is truly existent from Him who exists, alone existing from Him who alone exists, in as much as the like glory and power was eternally and conjointly begotten of the Father. ("Statement of Faith" 1-2. Found in Nicene and Post-Nicene Fathers. Series 2, Vol. 204.)
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 virute 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)
Ephraim the Syrian, c. AD 360
That Firstborn Who was begotten according to His nature, was born in another birth that was external to His nature; that we might know that after our natural birth we must have another birth which is outside our nature. For He, since He was spiritual, until He came to the corporeal birth, could not be corporeal; in like manner also the corporeal, unless they are born in another birth, cannot be spiritual. But the Son Whose generation is unsearchable, was born in another generation that may be searched out; that by the one we might learn that His Majesty is without limit, and by the other might be taught that His grace is without measure. For great is His Majesty without measure, Whose first generation cannot be imagined in any of our thoughts. And His grace is abundant without limit, Whose second birth is proclaimed by all mouths. (First Homily. "On Our Lord." Par. 1.)
Socrates Scholasticus, c. AD 450
This quaternion of revilers [Methodius of Olympia, Eustathius of Antioch, Apollinaris, and Theophilus] has maligned Origen, but not on the same grounds, one having found one cause of accusation against him, and another another. … For since one has attacked one opinion in particular, and another has found fault with another, it is evident that each has admitted as true what he has not assailed, giving a tacit approval to what he has not attacked. … But I affirm that from the censure of these men, greater commendation accrues to Origen. For those who have sought out whatever they deemed worthy of reproval in him, and yet have never charged him with holding unsound views respecting the holy Trinity, are in this way most distinctly shown to bear witness to his orthodox piety: and by not reproaching him on this point, they commend him by their own testimony.
Athanasius, the defender of the doctrine of consubstantiality, in his Discourses Against the Arians continually cites this author [Origen] as a witness of his own faith, interweaving his words with his own, and saying, "The most admirable and assiduous Origen," says he, "by his own testimony confirms our doctrine concerning the Son of God, affirming him to be co-eternal with the Father." Those therefore who load Origen with opprobrium, overlook the fact that their maledictions fall at the same time on Athanasius, the eulogist of Origen. (Ecclesiastical History VI:13)
Dionysius Petavius, d. 1652
Dionysius Petavius was a French Jesuit theologian. George Bull (other quotes from Bull below) references him as a "great man fully furnished with learning of every kind. Yet Bull says he is full of wonder that Petavius wrote the following, saying that it "freely gives up to the Arians, that which (if true) would very greatly tend to confirm their heresy." I agree with Bull that this could be twisted by Arians, but remember that the orthodox teaching disagreed with Arius only in the mode of origin of the Son of God as a separate person, not with the fact of his origin. The Nicene party contended that he already existed inside the Father, then was begotten or emitted from the bosom of the Father. The Arians argued that he was created from nothing and thus had a beginning. The difference between Petavius here and the early Christian writers he quotes is that they strongly emphasized the unity of substance with the Father, always carefully mentioning it. Prior to Origen (early third century), Christian writers regularly said that God was alone, but then they carefully point out that he was not really alone because the Word was inside of and in communion with him (see the quotes above). Petavius quotes them accurately here, but he does not emphasize the fact that the Word existed prior to being begotten inside of the Father. By not sharing their emphasis, he misrepresents them, but otherwise what he writes below represents the quotes you can find higher up on this page.
Accordingly there was this settled opinion in the minds of some of the ancients, touching the Godhead and the diversity of Persons in It, viz., that there is One supreme, unbegotten, and invisible God, who put forth, without, from Himself, as vocal and sounding, that Logos, that is, that Word, which He had laid up within, yet not, like a voice or sound, passing away and capable of being dissipated, but of such sort, as that, as though embodied and subsisting, It might in turn afterwards create all other things. Moreover, they said, that the Word was put forth by the Supreme God and Father at the time when He determined on creating this universe, in order that He might use Him as His assisting Minister. This opinion some intimate more clearly, others more obscurely. But these may be specially mentioned ; Athenagoras, Tatian, Theophilus, Tertullian, and Lactantius. Both these authors, however, and the rest, whom I have mentioned," [George Bull's note: and which of the primitve fathers had he not before mentioned?] "thought that the Father was superior to the Word, in age, dignity, and power; and although they asserted, that the Son was of the substance or nature of the Father, still they conceived that He had a beginning no less than the creatures; in other words, that He had by no means been a distinct Person from eternity. (Of the Trinity. i.5.7. cited [negatively] by George Bull in Defensio fidei Nicaenae c. 1685.)
George Bull, 1676-1686
George Bull was eventually a Church of England archbishop, and he had a Doctor of Divinity from Oxford.
What the Nicene fathers laid down concerning the divinity of the Son, in opposition to Arius and other heretics, the same in effect (although sometimes, it may be, in other words, and in another mode of expression) was taught without any single exception by all the fathers and approved doctors of the Church, who flourished before the council of Nice, even from the very times of the Apostles. (Bull, George D.D. Defensio fidei Nicaenae = a defence of the Nicene Creed : out of the extant writings of the Catholick doctors, who flourishsed during the three first centuries of the Christian church. Vol I. pp. x-xi. First printing c. 1685. Reprinted by John Henry Parker. [Oxford. 1851])
Suppose the Nicene fathers to have been unlearned and unlettered men, still they certainly were for the most part men of piety; and it is incredible that so many holy and approved men, meeting together out of all parts of the Christian world, could possibly have dishonestly conspired for the purpose of making an innovation on the received faith of the Church, respecting the primary article of Christianity; especially as, whatever may have been their lack of learning in other respects, they could not have been ignorant of the elementary doctrine of the most holy Trinity, which was wont to be taught even to catechumens, nor of what they themselves had received from their fathers concerning that subject. (ibid. p. 5)
In this passage, when [Faustus Socinus of Siena] says, that this was the belief of all the ancients down to the council of Nice, "that the Father of Jesus Christ alone is the one true God," if it be understood of that special prerogative of the Father, by which He alone is of Himself very God, then we acknowledge it to be most true. ... But if, on the other hand, this proposition, "The Father of Jesus Christ alone is the one true God," be taken altogether exclusively, so as to take away from Christ His true divinity, and to deny what was defined by the Nicene council, namely, that the Son is very God of very God ... then we contend that it is manifestly false that "all the ancients, down to the council of Nice, did so believe." (ibid. pp. 5-6)
That the Son of God was begotten of the proper substance of God, and is, therefore, very God of very God, is the sum and substance of the doctrine, which the Nicene fathers asserted against Arius. (ibid. p. 6)
Philip Schaaf, c. 1890
The bishops composing the Council of Nicea simply declared their faith in the Holy Spirit, without adding any definition; they were not met with any denial of the divinity of the Holy Spirit. This denial was first made by Macedonius, in the fourth century. (Nicene and Post-Nicene Fathers, series 2, vol. 2; "The Ecclesiastical History of Socrates Scholasticus" III:7, editor's note 476)
In Constantinople, during the Arian controversy, all classes, even mechanics, bankers, frippers, market women, and runaway slaves took lively part in the questions of Homousion and sub-ordination, of the begotten and the unbegotten. (History of the Christian Church, Vol. III, ch. IX, section 117)
Lee Irons, 2007
Traditionally, the doctrine of the eternal generation of the Son was supported by an appeal to the five Johannine texts in which Christ is identified as monogenes (Jn 1:14, 18; 3:16, 18; I Jn 4:9). As early as Jerome's Vulgate, this word was understood in the sense of "only begotten" (unigenitus), and the tradition was continued by the Authorized Version. However, most scholars of this century reject this understanding and believe, instead, that the idea behind the word is more along the lines of "only" (RSV) or "one and only" (NIV) . One of the main arguments is that the -genes suffix is related to the verb ginomai rather than gennao, thus acquiring the meaning "category" or "genus. ("The Eternal Generation of the Son." The Upper Register. Italics in original)
Perry Robinson, 2004-2017
You have to ask yourself, is there some common neutral concept of the Trinity to be had between theological systems? The answer is no. To see this you just need to think about whether say the Filioque (the F-word for the Orthodox) is an essential constituent of Trinitarianism or not. Catholics certainly seem to think so and not a few Protestants historically have also thought so. Of course the Orthodox don’t think so. How about whether the Father alone is autotheos? Is that essentially constituative of Trinitarianism? Calvin didn’t think so and plenty of other Reformed theologians followed him in that one way or another. And Catholics and Orthodox do think so, as expressly part of the Nicene faith. ("The Babel Answer Man." Energetic Procession blog.)