The Trinity Debate: More Than Just an Iota
The argument that the whole of trinitarian doctrine hinged upon one "iota" needs modification.
Does the doctrine of the Trinity hinge on one little letter? Sometimes people say that the difference between homoousia (ὁμοούσιος) and homoiousia (ὁμοιούσιος) makes or breaks orthodox trinitarianism. And the difference between these two words is one letter, the iota.
The argument needs modification, however, since Athanasius can say of the Son that he is "like the Father in every way" (ὅμοιος ὢν κατὰ πάντα τοῦ πατρὸς) when he writes Against the Arians (2.18). Added to this, Athanasius rarely uses the word ὁμοούσιος, preferring to use other descriptions of the Father and Son's relationship. And lastly, in his De Synodis, he also points out how homoiousios can represent Nicene doctrine:
"Those who say that the Son is like the Father in substance (homoiousios) do not seem to me to be far from the word homoousios, provided they confess that the Son is not a creature, but truly from the Father's substance, and that He is not of a different essence (heteroousios). For if they mean by 'like in substance' that He is truly from the Father and not alien to Him, then their intent aligns with ours, even if they hesitate at the term homoousios out of caution or misunderstanding." (§41).
Athanasius's words here should alert us to something vital. The argument amongst early Christians was not merely one of words and proper terminology.
What Was the Debate Really About?
The question that everyone had was: what judgments does Holy Scripture render about God and Christ? Notice that Athanasius can say that ὁμοιούσιος can represent ὁμοούσιος, provided that someone means "like in substance" because the Son is from the Father and intrinsic to his life.
The fact that Athanasius can freely say that the Son is "like the Father in every way" (ὅμοιος ὢν κατὰ πάντα τοῦ πατρὸς) in his diatribe against the Arians should clarify then that what Athanasius and the Fathers aimed to do was ensure that the church worshipped God in accordance with what Athanasius called the skopos of Scripture.
What was at stake in the mid-300s was not a grammatical hair splitter. The question centered on what positive and negative judgments Scripture makes about God and Christ. The word homoousia was used as a concept to represent that pattern of reading Scripture according to its scope in its proper order (akolouthia).
Why Homoousia Became Necessary
The reason why homoousia became necessary was that theologians like Arius would affirm the wording of the rule of faith, the ancient canon of truth. He would say that Christ is God, that he created everything, and that he was worthy of worship.
So why the big deal? The reason is that Arius used orthodox and even biblical language to render judgments completely different than the church had up until this point. For Arius:
The Son was a lesser God than the true God
The Son was the first product of creation through whom God created all other things, united to the Father by harmony of will but not naturally related
Christ was worthy of worship but the Father had greater glory and authority
As a consequence, Arius believed the Son shared in a harmony of will with the Father, as the firstborn of created things.
So Arius could use orthodox-sounding language but mean something quite different than orthodox theologians. So what happens when you both have the same Bible verses and can agree to the same verbal concepts like "the Son is divine," and "God created the universe through the Word"?
The answer is that you use a term that represents various judgments about God and Christ in Scripture to say this is exactly what we mean. Even though Arius uses similar words and concepts, the underlying judgments that he makes differ markedly from theologians like Athanasius of Alexandria..
The Heart of Nicene Theology
Ultimately for the Nicene Fathers, to confess that the Son was eternally begotten from the Father, not made, meant that the Son existed in a natural relation to the Father for all time. And Father begets Son—God begets God immaterially, eternally, and without change. For this reason, the Son is true God from true God, light from light, and so on.
The doctrine of eternal generation describes the underlying logic for why the Son is confessed to be consubstantial with the Father. The doctrine, by definition, rejects the Arian notion of a unity of will between two separate entities and the unequal glory of the Father and Son.
Did That Solve It?
Not really. Likely, the language of homoousia did not become clear to most Christians until the 400s. In 451, Chalcedon can use the terminology to explain that Christ is not only homoousia with the Father but also with us because of his dual natures. By this time, apparently, the language was well entrenched and usable for theology.
But during the 300s, other concepts came into play. Among the options included:
Homoiousia or image of the ousia (Basil of Ancyra, some bishops at the Council of Ancyra, 358, Council of Antioch 341, others too)
Homoia (Blasphemy of Sirmium in 357 and fourth Council of Sirmium in 358)
Anomoios or Heteroousia (associated with Aetius and Eunomius in the late 300s)
The homoiousians for the most part agreed with Nicene doctrine, but they often felt that the language of homoousia had too many materialistic connotations or had other concerns. So they preferred to say that the Son was like the substance of the Father in every way or the image of the ousia.
But as these things go, some grabbed the language of homoiousia and wrenched the concept into service of different judgments. Usually, though, this meant employing language like the Son is homoia the Father but not like the substance of the Father. Some were even so bold to say that the Son was unlike the Father and of a different ousia altogether.
The Council of Constantinople in 381 finally clarified what had been argued for decades. The positive and negative judgments about God and Christ as found in the rule of faith, the canon of truth, becomes associated with the concept homousia once again. And, it seems, this time it stuck.
