Trinitarians frequently claim that the trinitarian theology has been essential to Christianity from the beginning; whatever changes or developments there have been, we are told, are only refinements in the way this doctrine is expressed, and not changes to the actual doctrine itself. These claims, however, must be seen as representing either an ignorance of what the theological landscape of the early church actually looked like, or else brazen disregard for historical truth. We may easily recognize in the writings of the early fathers a clear development of doctrine respecting the identities of God, Jesus, and the Holy Spirit, and the relationships between them, involving not only massive changes in terminology, but also substantial changes to the underlying concepts themselves.
Firstly, we must note that early Christian writers, until the middle of the fourth century, were nearly unanimous in affirming that the one God is one person, the Father of the Lord Jesus Christ ; the main exceptions to this being gnostics and modalists . Early Christianity was home to a great deal of diversity, and while views that would lead into later trinitarianism developed slowly throughout the second through fourth centuries, the majority of Christians did not believe that Jesus literally pre-existed . Development in the direction of trinitarianism was advanced in the second century by the logos-theorists and apologists, such as Justin Martyr and Tertullian. Departing from the majority of Christians, they asserted that Jesus Christ was the logos and wisdom of God, begotten by God prior to or at the time of creation . Writers in this era spoke of the Son as being both ‘begotten’ and ‘created’ by the Father, using these terms interchangeably . The Son was viewed as being subordinate to the Father in several senses: as being chronologically after the Father , owing his existence to the Father , being under the authority of the Father and serving the will of the Father , not sharing the the transcendent divine attributes of the Father , and as being lesser than the Father in honor and glory . The Logos was seen as God’s instrument in the creation of the cosmos, and although this Logos was the Image of God who shared God’s own likeness, the Logos could do things that were, due to the transcendence of God, impossible for the one God to do, like appear to men as the Angel of the Lord . Although this Logos was “God” and “Lord”, he was expressly stated to be numerically distinct from the one God , ‘the Maker of all things’ , ‘the Most High’ , and ‘the Almighty’ , (all of which titles were reserved for the Father) and was sometimes referred to as ‘another God’ and a ‘second God’ besides the one God, the Father .
In the third century, Origen elevated the Son to the status of being co-eternal with the Father by popularizing a view called ‘eternal generation’, which came to eventually replace the temporal view of the Son’s generation held by earlier proto-orthodox writers . Origen also helped shape the language that would later be used to articulate trinitarian doctrine, including the use of the term ‘hypostasis’ to refer to a single discrete individual being, declaring that the Father, Son, and Holy Spirit were three hypostases ; only the hypostasis of the Father, the one God, however, was uncreated, with the Son being the greatest and eternal creature of the Father, and the Holy Spirit being next, having been created by God through the Son .
In the fourth century previously existing tensions between Origen’s views and the views of earlier logos-theorists boiled over in the Arian controversy. Arius was condemned for denying the Son’s eternality (as so many logos-theorists had) , and the Son was declared to be ‘of the same essence’ as the Father in the Nicene Creed. This vague terminology was employed to exclude Arius and his followers, but did not have a single clear meaning, but rather had many possible interpretations, acceptable to the many different non-Arian viewpoints represented at Nicea. In the following decades, however, fierce controversy broke out over how the term was to be understood. The term ‘homoousias’, ‘same being’, could be understood to either indicate generic sameness of nature among multiple individuals (as the alternative “semi-arian” term ‘homoiousias’ also indicated), or to indicate that the Father and Son were one individual . Recognizing the latter as modalistic , the conservative majority of bishops opted to replace the Nicene formula with another that could not be taken in such a modalistic way; this found expression through a number of non-nicene councils; for a couple decades, the Nicene Creed was totally repealed, and the pro-nicenes appeared to have lost . During this time important changes took place within the pro-nicene camp; whereas previously the pro-nicenes had advocated that ‘homoousias’ should be understood and accepted only in a generic sense , some pro-nicenes began to adapt nicene theology to affirm by this term that the Father and Son were together the same individual being and the same one God .
In this same era, some pro-nicene bishops began to advocate the doctrine that the Holy Spirit is also God and co-essential with the Father, thus introducing the concept of a trinity of persons all sharing one divine being; up until this point, a great deal of diversity had existed on how the Holy Spirit was viewed . By 381, with the older generation of pro-nicenes like Athanasius dead, a newer generation had taken the helm of the pro-nicene party, and for the first time in history advocated a triune God, or one God who is Father, Son, and Holy Spirit , repudiating the older view that the one God is uni-personal, the Father, and that the Son is a numerically distinct individual besides Him . Due to a change in imperial politics, this small party was thrust into power, and was thus able to define orthodoxy for the entire Roman Empire. While many bishops continued to hold a subordinationist christology and/or denied the Godhood of the Holy Spirit, the opinion of these conservatives was ignored, and the new revised ‘Nicene Orthodoxy’ became the official trinitarian orthodoxy of the church moving forward. Enforced by the sword, dissent was slowly killed by force as the Roman Empire crumbled and, with the eventual defeat of (the previously ‘orthodox’) Homoian unitarian subordinationism among the Barbarians in the 8th century, Europe entered the Dark Ages firmly trinitarian .
Ultimately the fact that trinitarianism as we know it today is the result of a long and painful process of theological evolution is unavoidable from the historical data. Leaving behind the Bible’s own answers to questions of christology, proto-trinitarian speculation resulted in centuries of bitter infighting among professing Christians, which was only finally resolved by the violent intervention of Roman Imperial authorities in favor of the newly christened ‘orthodoxy’ of trinitarianism. The history of this development sees one significant conceptual change after another, with those holding to an older stage of development quickly becoming the heretics of the next generation. It is the job of those seeking the true religion of Jesus and his apostles to distinguish between these later wildly speculative developments and the religion of the Jewish man, Jesus the Nazarene.
 See the ‘rule of faith’ as attested to by Irenaeus, Tertullian, and Origen, as well as the Creed of Nicea, the Macrostich, the Homoian Creed, all of which begin with the confession “We believe in one God, the Father Almighty…” as well as a collection of testimonies from the writings of various nicene and ante-nicene fathers available here. See a comparative chart of the ‘rule of faith’ as given by various early authors here.
 “I know that there is one God, Jesus Christ; nor except Him do I know any other that is begotten and amenable to suffering.” Zephyrinus (d. 217 CE), a Sabellian, as recorded by Hippolytus in Refutation of All Heresies, Book 9. Gnostic denial of the identity of the one God with the Father, and the ‘catholic’ unitarian position against this, is especially clear in Irenaeus’s Against Heresies.
 “For there are some, my friends,” I said, “of our race [Christians], who admit that He is Christ, while holding Him to be man of men; with whom I do not agree, nor would I, even though most of those who have the same opinions as myself should say so; since we were enjoined by Christ Himself to put no faith in human doctrines, but in those proclaimed by the blessed prophets and taught by Himself.” (Justin Martyr, Dialogue With Trypho, 48) “A second class are those who know nothing but Jesus Christ and Him crucified, considering that the Word made flesh is the whole Word, and knowing only Christ after the flesh. Such is the great multitude of those who are counted believers.” (Origen, Commentary on John 2.3)
 See Justin Dialogue With Trypho Ch 61 and 129; Theophilus of Antioch To Autolycus, 2.22; Tatian Address to the Greeks, Ch 5.
 See Tertullian, Against Hermogenes Ch 3 and 18; Origen, Commentary on John, 2.6.
 See Novatian On the Trinity, Ch 31; Hippolytus, Refutation of All Heresies, Ch 10, and Against Noetus, Ch 10-11; Tertullian, Against Hermogenes Ch 3.
 See Justin, Dialogue With Trypho Ch 29, 61, 62, 128; Novatian On the Trinity Ch 31; Origen Commentary on John 2.6; Tatian Address to the Greeks, Ch 5; Hippolytus, Refutation of All Heresies, Ch 10.
 “When Scripture says, ‘The Lord rained fire from the Lord out of heaven,’ the prophetic word indicates that there were two in number: One upon the earth, who, it says, descended to behold the cry of Sodom; Another in heaven, who also is Lord of the Lord on earth, as He is Father and God; the cause of His power and of His being Lord and God.” (Dialogue With Trypho, Chapter 29) “I shall attempt to persuade you, since you have understood the Scriptures, [of the truth] of what I say, that there is, and that there is said to be, another God and Lord subject to the Maker of all things; who is also called an Angel, because He announces to men whatsoever the Maker of all things— above whom there is no other God — wishes to announce to them.” (Ibid, Chapter 56) See also Justin Dialogue With Trypho, Ch 29, 56, 60, 61, 113, 125, 126, 127; “Moreover, the Son does nothing of His own will, nor does anything of His own determination; nor does He come from Himself, but obeys all His Father’s commands and precepts; so that, although birth proves Him to be a Son, yet obedience even to death declares Him the minister of the will of His Father, of whom He is. Thus making Himself obedient to His Father in all things, although He also is God, yet He shows the one God the Father by His obedience, from whom also He drew His beginning.” Novatian On the Trinity, Ch 31.
 See Justin Dialogue With Trypho, Ch 56, 60, 127; Irenaeus Demonstration of the Apostolic Preaching; Tertullian Against Praxeas Ch 16; Novatian On the Trinity Ch 17, 18.
 See Tertullian Against Hermogenes, Ch 18.
 See Justin Dialogue With Trypho, Ch 56, 60, 127; Irenaeus Demonstration of the Apostolic Preaching; Tertullian Against Praxeas Ch 16; Novatian On the Trinity Ch 17, 18.
 “You perceive, my hearers, if you bestow attention, that the Scripture has declared that this Offspring was begotten by the Father before all things created; and that which is begotten is numerically distinct from that which begets, any one will admit.” Justin Martyr, Dialogue With Trypho, Chapter 129; see also Ibid, Ch 128.
 “I shall attempt to persuade you, since you have understood the Scriptures, [of the truth] of what I say, that there is, and that there is said to be, another God and Lord subject to the Maker of all things; who is also called an Angel, because He announces to men whatsoever the Maker of all things— above whom there is no other God — wishes to announce to them.” Justin Dialogue With Trypho, Chapter 56.
 “Grant that there may be some individuals among the multitudes of believers who are not in entire agreement with us, and who incautiously assert that the Saviour is the Most High God; however, we do not hold with them, but rather believe Him when He says, “The Father who sent Me is greater than I.” We would not therefore make Him whom we call Father inferior — as Celsus accuses us of doing — to the Son of God.” Origen Contra Celsum, 8.14.
 See the ‘rule of faith’ as attested to by Irenaeus, Tertullian, and Origen, as well as the Creed of Nicea, the Macrostich, the Homoian Creed, all of which begin with the confession “We believe in one God, the Father Almighty…”. See a comparative chart of the ‘rule of faith’ as given by various early authors here.
 “And although we may call Him a second God, let men know that by the term second God we mean nothing else than a virtue capable of including all other virtues, and a reason capable of containing all reason whatsoever which exists in all things, which have arisen naturally, directly, and for the general advantage, and which reason, we say, dwelt in the soul of Jesus, and was united to Him in a degree far above all other souls, seeing He alone was enabled completely to receive the highest share in the absolute reason, and the absolute wisdom, and the absolute righteousness.” Origen, Contra Celsus, Book 5.39; see also Justin, Dialogue With Trypho, Ch 56.
 See Origin First Principles, 1.4, compare Novatian On the Trinity, Ch 31; Hippolytus, Refutation of All Heresies, Ch 10, and Against Noetus, Ch 10-11; Tertullian, Against Hermogenes Ch 3.
 See Commentary on John, 2.6 and 10.21.
 “We consider, therefore, that there are three hypostases, the Father and the Son and the Holy Spirit; and at the same time we believe nothing to be uncreated but the Father. We admit, as more pious and as true, that the Holy Spirit is the most honored of all things made through the Word, and that he is [first] in rank of all the things which have been made by the Father through Christ. Perhaps this is the reason the Spirit too is not called son of God, since the only begotten alone is by nature a son from the beginning. The Holy Spirit seems to have need of the Son ministering to his hypostasis, not only for it to exist, but also for it to be wise, and rational, and just, and whatever other thing we ought to understand it to be by participation in the aspects of Christ which we mentioned previously.” (Origen, Commentary on John 2.6)
 “But as for those who say, ‘There was when He was not’, and, ‘Before being born He was not’, and that He came into existence out of nothing… or is subject to alteration or change, these the Catholic and apostolic Church anathematizes.” (Anathemas of the Nicene Council) While Arius possibly innovated in saying that the Son was created ‘ex nihilo’, out of nothing, he was certainly not the first to teach that there has been a point before the person of the Son existed, see footnote #6.
 Hilary of Poiters clearly distinguishes between these multiple ways of taking ‘co-essential’ in his De Synodis. That Hilary acknowledges that what he and the pro-nicenes actually mean by ‘same essence’ is the same thing as the later so-called ‘semi-arians’ meant by ‘like essence’ is very significant, for this reveals that at this time, ‘like essence’ was not considered heresy by the pro-nicenes, but just was only rejected by them as being a poor way of expressing the same idea they intended by ‘same essence’. Later condemnation of the ‘Homoiousian’ ‘semi-arians’ by triniatarians, then, really represents a condemnation of the early pro-nicenes like Athansius as well, since they acknowledged an agreement of doctrine with these “semi-arians” in all but wording. See also Athanasius, De Synodis, 41.
 Even Hilary, Athanasius, and Basil recognized a numerical or individual unity of essence as Sabellian, (that is, modalistic). “For neither do we hold a Son-Father, as do the Sabellians, calling Him of one but not of the same essence, and thus destroying the existence of the Son.” Athanasius, Statement of Faith. And Basil the Great said “This term [co-essential] also corrects the error of Sabellius, for it removes the idea of the identity of the hypostases, and introduces in perfection the idea of the Persons. For nothing can be of the same substance with itself, but one thing is of same substance with another.” (Letter LII) These quotes demonstrate that the numerical or individual sense of ‘co-essential’ was seen as Sabellian, and that Athanasius and Basil saw the term’s intended meaning as a generic unity of nature only. They were sure that the term ‘homoousias’, despite being open to this Sabellian meaning, would always be properly qualified as a conceptual equivalent to ‘homoiousias’; we see that within only the span of a generation, however, their pet term was already being taken in the modalistic sense that their opponents warned it would be.
 A number of local councils first contravened the Nicene Creed, before finally, in 359, the then ‘ecumenical’ councils of Ariminum & Seleucia officially took the Nicene Creed off the books and replaced it with the ‘Homoian’ formula, which eschewed the philosophically dense language of ‘ousia’ in favor of simply defining the Son as ‘like the Father’ and allowing a more ante-nicene view, like that of the logos-theorists, to flourish again for a brief time.
 See Hilary, De Synodis, 66-72, Athanasius De Synodis 41, and footnote #22 above.
 See Hilary in On the Trinity, where we can see his drastic departure from the careful anti-Sabellian qualification he gave in his earlier De Synodis. “I and the Father are One John 10:30, are the words of the Only-begotten Son of the Unbegotten. It is the voice of the One God proclaiming Himself to be Father and Son; Father speaking in the Son and Son in the Father.” (On the Trinity, Book 2). See also the writings of Marius Victorinus and Gregory Nazianzen.
 “But of the wise men amongst ourselves, some have conceived of him as an Activity, some as a Creature, some as God; and some have been uncertain which to call Him, out of reverence for Scripture, they say, as though it did not make the matter clear either way. And therefore they neither worship Him nor treat Him with dishonour, but take up a neutral position, or rather a very miserable one, with respect to Him. And of those who consider Him to be God, some are orthodox in mind only, while others venture to be so with the lips also. And I have heard of some who are even more clever, and measure Deity; and these agree with us that there are Three Conceptions; but they have separated these from one another so completely as to make one of them infinite both in essence and power, and the second in power but not in essence, and the third circumscribed in both; thus imitating in another way those who call them the Creator, the Co-operator, and the Minister, and consider that the same order and dignity which belongs to these names is also a sequence in the facts.” Gregory Nazianzen, Oration 31. We see here that Gregory, a Cappadocian and one of the leading figures arguing for the view that the Holy Spirit is God, makes no attempt to claim his position as the historical orthodoxy of Christians, but freely admits great diversity of opinion on the matter. Of those who thought the Spirit was a creature, we may especially recall the influential Origen, see Commentary on John 2.6.
 See Augustine’s writings in On the Trinity and in his Debate with Maximinus (a Homoian), wherein the one God is expressly treated as a single personal entity who is Father, Son, and Holy Spirit. See also Hilary in On the Trinity, where we can see his drastic departure from the careful anti-Sabellian qualification he gave in his earlier De Synodis. “I and the Father are One John 10:30, are the words of the Only-begotten Son of the Unbegotten. It is the voice of the One God proclaiming Himself to be Father and Son; Father speaking in the Son and Son in the Father.” (On the Trinity, Book 2). See also the writings of Marius Victorinus and Gregory Nazianzen on the Trinity, and the later pseudo-athanasian creed which came to summarize this modalistic trinitarianism.
 This repudiation of the view that the one God is one person, the Father of Jesus, and Jesus another distinct from the one God, can be seen especially in Augustine’s interactions with Maximinus in their Debate, and in the ruling if the council of Rome in 382 as recorded by Theodoret; see Church History, 5.11. Eunomius’s reaction to the nicene victory under Theodosius I also indicates that the opponents of the Nicene party saw themselves as arguing against a theology which taught that the one God is triune, and not particularly the Father; so also with Maximinus in his debate with Augustine.
 See the proscriptions of heresy in the Theodosian code. Byzantine anti-heresy laws gradually strengthened against all non-trinitarian views, as the Western Roman Empire fell to the Homoian Goths and Vandals, giving a brief respite of religious liberty, before the restored rule of catholics under the Franks again brought strict medieval anti-heresy laws, forcing non-trinitarians underground until the Protestant Reformation.