The Rise and Fall of the Homoiousianism


After Nicaea, the ‘Arian’ Controversy raged for another 55 years. During that period, ‘Arianism’ dominated the church. But ‘Arianism’ consisted of several strands. This article explains the theology of the Homoiousians, which was one of those strands. Homoiousian means ‘similar substance’ and was used to say that the Son’s substance is similar to the Father’s.


This article series is largely based on two books:

RH = Bishop RPC Hanson
The Search for the Christian Doctrine of God –

The Arian Controversy 318-381, 1987

LA = Lewis Ayres
Nicaea and its legacy, 2004

Ayres is a Professor of Catholic and Historical Theology

A Compromise

It is often claimed that Homo-i-ousianism (similar substance theology) arose as an attempt to reconcile two opposing teachings, namely: and Homo-ianism:

Homo-ousianism, which comes from the word homo-ousios in the Nicene Creed of the year 325. It means “same substance” and was used to say that the Son’s substance is the ‘same’ (ὁμός, homós) as the Father’s.  If the Son’s substance is the same as the Father’s, then the Son must be co-equal and co-eternal with the Father.

Homo-ianism, on the other hand, refused to use the term substance (οὐσία, ousía). It believes that the Son is “like” (ὅμοιος, hómoios) the Father but subordinate to Him.

It is then proposed that similar substance theology (Homo-i-ousian) was an attempt to reconcile the same substance theology (Homo-ousian) theology with the Homoian notion of similarity. For example, “Gwatkin described the group as a ‘Semi-Arian position modified by an Athanasian influence.” (RH, 349) (Athanasius was the great defender of the same substance theology.)

A Persistent Strand

However, recent scholarship does not accept that Homo-i-ousianism was an attempt to reconcile the two other theologies. Homo-i-ousianism was “most prominently associated with … Basil of Ancyra” (RH, 349) and “the term homoiousios plays no role in Basil’s surviving texts” (LA, 150). This implies that such a compromise was not the purpose. More recently, Lewis Ayres proposed that Homo-i-ousianism was not merely a compromise but “a significant and persistent strand in earlier eastern theology.” (LA, 150)

There are indications that this theology was a restatement or development of the theology of Eusebius of Caesarea, as stated in the letter he wrote to his home church after the Nicene Council, to explain why he accepted that Creed:

Ritter described Homoiousianism “as the right wing of the Eusebian party.” (RH, 349)

“Basil … prefers the term ‘image of the ousia’ to define the Son’s relationship to the Father; it is worth noting that this term was favoured by Eusebius of Caesarea … and also is found in the Second (‘Dedication’) Creed of Antioch 341.” (RH, 353)

Eusebius was “universally acknowledged to be the most scholarly bishop of his day.” (RH, 46) Eusebius was the most influential theologian present at the Council of Nicaea in AD 325.

A Response to Neo-Arianism

Both Lewis Ayres and R.P.C. Hanson stated that the formulation of Homoiousian theology in 358 by a council of bishops called by Basil of Ancyra was a response to, what Ayres calls, “the emerging shape of Heterousian theology” in the form of the creed of “Sirmium 357,” which was based on the teachings of Aetius. Hanson refers to this as “Neo-Arianism” and as “a new and radical theology” that appears for the first time in the extant ancient records in the form of the “Second Creed of Sirmium of 357,” afterward approved by a larger synod at Antioch (probably in AD 358). ‘Neo-Arianism’ may be an appropriate name because it was “a development” of Arius’ theology. (RH, 348; LA, 149-150)

“Basil’s council sent a delegation to the Emperor Constantius … and this embassy met with success.” The Emperor condemned “Aetius and his teaching” and exiled Aetius and his supporters. This supports the view that this formulation of homo-i-ousianism was particularly intended to oppose the Neo-Arians. (LA, 152-153)

Homo-i-ousian Theology

“The statement which emerged from this council … marks the emergence of a new and coherent theological point of view. This is the theology of those whom Epiphanius, quite undeservedly, calls ‘Semi-Arians’, but who are usually today thought of as Homoiousians, a designation which is more accurate.” (RH, 348-9)

This statement was written by Basil of Ancyra himself (LA, 150) and “is of the highest importance for an understanding of Homoiousian theology.” (RH, 350) It includes “nineteen anathemas which reveal more clearly the position which Basil is attacking.” (RH, 355)

Against Homoian Theology

Homoianism was a dominant Christology during the mid-fourth century. For example, the creeds of the councils of Sirmium in 358, Ariminum in 359, and the key council at Constantinople in 359 / 360 were homoian. It refused to use ousia (substance) language in the formulation of any statement of faith because the Bible does not say anything about God’s substance. Against them, Basil insisted that substance language is necessary to reflect the closeness of the Father and Son expressed by the concepts “Father/Son” and “begotten.” He wrote:

“God must be both Father and creator” (of His Son) (RH, 353). “If we remove this resemblance of ousia,” the Son is merely a created being; “not a Son.” (RH, 353, 354)

Since human sons are like their fathers, the Son of God is like His Father (RH, 352). “The salient irreducible element” in a father/son relationship is “the begetting of a living being that is like in ousia.” (RH, 352-3)

“If the Father gives the Son to have life in himself (John 5:26) … then the Son must have the same life and thus have ‘everything according to essence and absolutely as does the Father’.” (LA, 152)“

Against Homoousian Theology

It is often claimed that the term homo-ousios in the Nicene Creed means “one substance,” namely, that the substance of the Son is one and the same as the Father’s substance. It is on this basis alone that we can argue that the Son is co-eternal and co-equal with the Father. However:

Hanson concluded that “we can … be pretty sure that homoousios was not intended to express the numerical identity of the Father and the Son.” (RH, 202)

Philip Schaff stated: “The term homoousion … differs from monoousion. … and signifies not numerical identity, but equality of essence or community of nature among several beings. It is clearly used thus in the Chalcedonian symbol, where it is said that Christ is “homoousios with the Father as touching the Godhead, and homoousios with us [and yet individually distinct from us] as touching the manhood.”1Philip Schaff, History of the Church volume 3 (Grand Rapids, MI: Eerdmans Publishing Co., 1981 edition) pp.672-673.

The idea of “one substance,” therefore, developed later. In the Homo-ousianism of the Nicene Creed, the Son’s substance is identical with the Father’s, meaning two substances that are identical. 

This is based on a material interpretation of the terms “Father,” Son,” and “only-begotten,” as if God has a body and bodily gave existence to the Son, comparable to how human sons are brought forth. Consequently, the Son’s substance is identical to the Father’s. For example:

“Anathema 13 links the error of thinking of the Father/Son relationship in corporeal terms with that of making the Son identical with the Father.” (RH, 356)

Homo-i-ousianism did not accept this notion. (RH, 352-3) In Homo-i-ousianism, the Son is subordinate to the Father. (RH, 355) If this is true, then the Son’s substance cannot be identical to the Father’s. Basil explained:

“The Son is like the Father in ousia but not identical with him.” (RH, 352-3). 

“As He … was in the likeness of men (John 1:14) … yet not a man in all respects;” “not identical with human nature,” for example. He was not born through natural conception, “so the Son … is God in that he is Son of God,” was “in the form of God,” and is “equal to God (Phil 2:6, 7),” “but not identical with the God and Father.” (RH, 354)

Anathema 13 “damns him who declares … that the Son is identical with the Father … This is manifestly directed against N (the Nicene Creed).” (RH, 355)

Against Sabellian Theology

In Sabellianism, the Son is not a distinct Person. Rather, the Father and Son are parts of one Person. Basil responded:

“This argument that God must be both Father and creator and that the likeness in ousia is necessary … as a safeguard against Sabellianism: that which is like can never be the same as that to which it is like’.” (RH, 353)

The anathemas also attack the apparent Sabellianism of Marcellus of Ancyra. (RH, 355)

Against Neo-Arian Theology

In Neo-Arianism, which was “a new and radical” (RH, 348) adaptation of Arius’ theology, the terms “Father,” Son,” and “only-begotten” symbolize that the Son is the very image of the Father, but not in a corporeal (material) sense. For that reason, in this view, “the Son is ‘unlike(anhomoios) in ousia to the Father” Ayres refers to this as “Heterousian (different substance) theology.” (LA, 149) For example, Basil’s “Anathema 12 strikes him who declares that the Son’s likeness to the Father consists in power but not in ousia.” (RH, 355)

Homo-i-ousianism was somewhere between the Homoousian (same substance) view and the Neo-Arian (different substance) view. 

The End of this Theology

“In AD 359 Constantius decided to emulate his father’s action in calling Nicaea and summon a general council. … A small group of bishops met at Sirmium to draw up a draft creed for discussion. Those present included not only Basil, but also some who were far more suspicious of ousia language. The creed on which they finally agreed … asserts that all ousia language should be avoided. … … Thus, although Basil of Ancyra was influential with the imperial authorities at one point during 358–9, it was not for long, and he never seems fully to have overcome long-standing Homoian influence at court. (LA, 157-8)

Constantius was becoming somewhat hostile to the influence of all of the new movements which had sprung up after the Nicene council. The result was that the Homoiousians disappeared from the stage of history and the struggle to define Church dogma became a two-sided battle between the Homo-ousians and the Homo-ians.


The 55 years of Controversy after the Nicene Creed of 325 revolved specifically around the word homoousios. Since, in the Nicene Creed, this term was an interpretation of the term “begotten,” the differences between the various Christological views are essentially different interpretations of the terms “Father,” “Son,” and “only-begotten.” These interpretations result in different views with respect to the substance of the Son, on the basis of which the five views may be summarized:

      • Sabellianism = One and the same substance
      • Homoousian = Distinct but identical substance
      • Homoiousian = Similar in substance
      • Neo-Arianism or Heteroousians = Unlike in substance
      • Homo-ianism refuses to refer to substance.

Other Articles

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    Philip Schaff, History of the Church volume 3 (Grand Rapids, MI: Eerdmans Publishing Co., 1981 edition) pp.672-673.