The fourth-century Christian era displays and contributes to some of the most essential principles of classical Trinitarian and Christological dogma and the formation of creedal confessions. Theologians and the Church may still use these features as starting points to communicate these doctrines. Johannes Quasten refers to the Nicene heritage up to Chalcedon as the “Golden Age” of Patristic thought. The Nicene and pro-Nicene heritage continued to inform and govern the general practice of theological formation and theological thought even up to the Chalcedon formula.
As we begin with the language of Nicaea and pro-Nicene theology, I mean to convey a few items. These early Christological and Trinitarian disputes extended well beyond a simple affirmation or denial of the divinity of the Son. The Synod of Nicaea and the aftermath of the Nicaea formula witnessed much dispute and clarity in the subsequent years. It seems that many theologians look at Nicaea as ushering in the victory of Christian theology. As Athanasius defeats Arius, according to the common trope, Nicaea becomes the Orthodox Athanasian victory. However, the reception and retelling of Nicaea in the generations that follow are not so simple. The Creed brought about some confusion that required much clarity. As Arius and Athanasius appear to be front-runners in the initial formation of Nicaea, they are neither primary figures afterward. “Nicaea” means both the creedal formulation, the historical events surrounding 325 AD, and a theological culture that followed. And, pro-Nicene refers to a particular window that includes second and third generation defenders and advocates of the Nicene vision.
In 2004, Lewis Ayres defined pro-Nicene Trinitarianism in this way:
By ‘pro-Nicene’ I mean those theologies, appearing from the 360s to the 380s, consisting of a set of arguments about the nature of the Trinity and about the enterprise of Trinitarian theology, and forming the basis of Nicene Christian belief in the 380s.
Pro-Nicene Trinitarian theology assumed a few central theological items that would be generally representative. These three items are not the sole features, but they serve, at least, as the basis for a pro-Nicene heritage:
person and nature distinction
eternal generation of the Son
While refraining from a reductionist set of arguments, I argue these three items can serve as a central base for pro-Nicene theology rather than a summary of pro-Nicene theology.
Person and Nature Distinction in Trinitarian Discourse
What language do early Christians use to describe the unity of essence and diversity of persons when describing the Triune God? Essence and personhood were described by a variety of words (οὐσία, ὑπόστασις, φύσις, natura, susbstantia, persona, and more). Early Christians forged a theological lexicon within the Nicene heritage. When reading one particular Father, they may use any one of these words in a different way than other figures in this era. So, great care rests upon the historian and theologian to work together to see the variety and often non-uniform manner early Christian theologians described God as one and God as three. There are standard and repeating statements among pro-Nicene figures that display this distinction in person. Often one will see a general expression that the Father is not the Son, the Son is not the Father, and the Spirit is neither Father nor Son.
Gregory of Nyssa’s brief letter to Eustathius, On the Holy Trinity, makes simple the unity of nature and distinction of personhood. For, that appears to be the very charge against Nyssen.
There are two brought forward together in the accusation against us; one that we divide the persons; the other, that we do not employ any of the names which belong to God in the plural number, but (as I said already) speak of the goodness as one, and of the power, and the Godhead, and all such attributes in the singular. With regard to the divine of the persons, those cannot well object who hold the doctrine of the diversity of substances in the divine nature. For it is not to be supposed that those who say that there are three substances do not also say that there are three persons. So this point only is called in question: that those attributes which are ascribed to the divine nature we employ in the singular.
These initial set of comments display the two different charges given to Nyssen. Charge one is a division of persons, and charge two is divine names are not employed in the plural. Gregory carefully notes that the titles that describe the divine nature do not appear in the singular. Thus, it is not three powers but one power. It is not three goodnesses but one goodness. Nyssen’s teaching is to uphold the persons co-equally sharing the one divine essence without division. These qualities unequivocally and wholly describe the single divine nature. That they are singular and display the single essence of God.
Augustine’s Sermon 52 (c. 410) concerns the story of Jesus’s baptism. As he comments on the descent of the Dove, Augustine notes at some length the inseparable Trinity and one God. To describe God in nature is to describe God as one. To describe God in personhood is to describe God as three. All that is of the Father eternally is now of the Son eternally so that the Son possesses the full essence of God with no division and no creation. Click To Tweet
In this single statement, the unity of God, the unity of three irreducible persons, and the inseparable activity form a fundamental doctrinal rule. According to Ayres, “the formulae we have seen in Sermon 52 are austere: they are an attempt to set out appropriate rules for an orthodox reading of Scripture and for orthodox talk of God.”
Eternal Generation of the Son
The eternal generation of the Son is an eternal act of the Father to beget the person of the Son, not the nature of God, so that the Son possesses no origin of existence. All that is of the Father eternally is now of the Son eternally so that the Son possesses the full essence of God with no division and no creation. For the pro-Nicene heritage, to be begotten implies an eternal activity of the Father begetting the Son with no time of origin of the Son’s existence. Part of doing so for the Nicene heritage is that “Fatherness” is not part of the essence but part of personhood. To name “Fatherness” as inherent in essence, then all three persons equally share and possess “Fatherness”—and this is not so.
Athanasius uses Proverbs 8:22 and 8:25 to support the eternal generation and the finite incarnation of the Son. Written in 350/1, merely twenty-five years after the initial Synod, Athanasius wrote On the Council of Nicaea (De Decretis) to address several items, including the dissatisfaction of the Nicene ousia-language, Eusebian critics, and how to appeal to homousios as a non-scriptural term.
In De Decretis § 13–14, Athanasius responds to how the Son can be begotten and not created. His Eusebian interlocutors quote Proverbs 8:22 (“The Lord has created me as a beginning of his ways, for his works”). He credits the Eusebians as saying that the Son is one of the creatures of the Father (De Dec 13). For Athanasius, the Son does not exist externally to the Father but from the Father who has begotten him (De Dec 13). If the Son is created, then the Son exists externally in relation to the Father; but if the Son is begotten, then the Son is of the Father.
Therefore: if Son, then not a creature; if a creature, then not Son. For great is the difference between these. The same one cannot be both creature and Son, as if his being can be considered to be both from God and from outside God.
As Athanasius considers Proverbs 8:25 (“Before all hills he begets me”), he offers a two-fold partitive reading of Proverbs 8:22–25. Of course, he suggests, Proverbs 8:22 is important for Christological dogma for it points to the incarnation. Proverbs 8:25, on the other hand, displays eternal begetting of the Father. For the Son to be created, he therefore resides outside the Father. As it corresponds to Proverbs 8:22, Athanasius says: “He is indeed said to be created also, but that is when he became a human being; for this is what properly belongs to being human.” He further notes,
As to the person, it is that of the Savior: but it is said when he takes a body and then says, “The Lord created me as a beginning of his ways for his works.” For just as it well befits the Son of God to be eternal and to be in the bosom of the Father, so also, upon becoming human, it is fitting for him to say, “The Lord created me”.
Athanasius discerns the proper time of the Son. Proverbs 8:22, 25 displays both the eternal relations with the Father and the finite localized time of his incarnation.
Proverbs 8:22 is likewise the extended focus of Athanasius in Orations against the Arians, most notably in §2.2, 2.3, and 2.18–82. For the Son to be eternally begotten, the Son likewise is of the Father. For if the Son is created by the Father, then he is outside the Father and not proper to his essence. When theologians begin speaking of the Son as part of the creation of the Father, early Christian theologians observe what this communicates about the Father. Athanasius merely hints towards this concept. If the Father created the Son and is outside the Father, then God is no longer an eternal Father. To deny the eternal generation of the Son places the immutability of God in turmoil. To deny the eternal generation of the Son places the immutability of God in turmoil. Click To Tweet
In a lengthy quote, he teases out how the Son and the Father must be in eternal relation. For, if the Son and the Father are not eternally relating to one another, the Father ceases to be Father and is only understood to be creator. The Son is no longer of the Father as his own but exists outside of the Father. To diminish the eternal generation of the Son in turn diminishes the eternal title of the Father and diminishes the immutability of the eternal nature. As it relates to Proverbs 8:22–25, to create is secondary to the Father’s begetting.
Inseparable Activity in a Unity of Being
Divine simplicity and inseparable activity relate together. Within a pro-Nicene vision of God, simplicity and indivisibility comprise a vision of God. God is whole, without parts. If the nature of God, at least in these two subsequent examples, serve as the basis to describe the activity of God, we may assume a sense of mystery as we describe the inseparable activity. Simply put, for a pro-Nicene vision, since God’s essence is simple and non-composition and since the divine essence co-equally subsists without division in the three persons, then inseparable activity is the mysterious activities of God ad intra and ad extra whereby all three persons act in relation to the other because of the shared and simple nature. Within a pro-Nicene vision of God, simplicity and indivisibility comprise a vision of God. God is whole, without parts. Click To Tweet
In On the Holy Trinity, Nyssen comments on the singular activities of the Trinitarian persons. “If, on the other hand, we understand that the operation of the Father, the Son, and the Holy Spirit is one, differing or varying in nothing, the oneness of their nature must needs be inferred from the identity of their operation.” The single nature of God warrants the single activity of the persons.
As Nyssen quotes from John 17, we can’t merely attribute one particular action to a single person when indeed there is a specific text that highlights this activity to the Father. However, each person gives sanctification, life, light, comfort, and graces. The one activity can be accomplished by the persons. However, Nyssen anchors this unity of activity in the simplicity of God’s nature.
The commonality of shared attributes in the persons stems from the simplicity of God’s nature. This simplicity then warrants a single operation. Since we say, then, that the Father, Son, and Spirit act as one, then we can likewise affirm that the Godhead is one.
Basil of Caesarea, in Letter 189, again builds the case that the inseparable activity is predicated upon a single divine nature. If we observe the Father, Son, and Spirit display activities different from the other, then we may assume a distinction of nature. Thus, a difference in nature suggests a difference in operation.
We are therefore of necessity guided in the investigation of the divine nature by its operations. Suppose we observe the operations of the Father, of the Son, of the Holy Ghost, to be different from one another, we shall then conjecture, from the diversity of the operations that the operating natures are also different. For it is impossible that things which are distinct, as regards their nature, should be associated as regards the form of their operations; fire does not freeze; ice does not warm; difference of natures implies difference of the operations proceeding from them. Grant, then, that we perceive the operation of Father, Son and Holy Ghost to be one and the same, in no respect showing difference or variation; from this identity of operation we necessarily infer the unity of the nature.
Basil anchors inseparable activity in the doctrine of simplicity than detailing proper activities or the appropriation of activities to persons. There exists a unity of nature between the three persons, and thus, a unity of activity follows suit.
In light of all this, we can safely summarize our Nicene heritage by emphasizing (1) a clear distinction of person and nature in our trinitarian language, (2) a clear expression of the eternal generation of the Son, and (3) a clear expression of the Trinity’s inseparable operations on account of a unity of Being. To be “pro-Nicene” is nothing less than to express these three characteristics.
 Lewis Ayres, Nicaea and Its Legacy: An Approach to Fourth-Century Trinitarian Theology (Oxford: Oxford University Press, 2004), 1.
 Johannes Quasten, Patrology: The Golden Age of Greek Patristic Literature from the Council of Nicaea to the Council of Chalcedon, vol. 3 (Westminster, MD: Christian Classics, 1986); Johannes Quasten, Patrology: The Golden Age of Latin Patristic Literature from the Council of Nicaea to the Council of Chalcedon, vol. 4 (Westminster, MD: Christian Classics, 1983).
 Mark S. Smith, The Idea of Nicaea in the Early Church Councils, AD 431-451, Oxford Early Christian Studies (Oxford: Oxford University Press, 2019).
 Anatolios, Retrieving Nicaea, 18.
 Ayres, Nicaea and Its Legacy, 6.
 See Gregory Nazianzen, Or. 31.9; Gregory Nyssen, Ref. 5–6; Augustine, Serm. 52.2. Ayres, Nicaea and Its Legacy, 295.
 Gregory of Nyssa, On the Holy Trinity.
 “The Father, Son, and Holy Spirit are a Trinity inseparable; one God not three Gods. But yet so one God, as that the Son is not the Father, and the Father is not the Son, and the Holy Spirit is neither the Father nor the Son, but the Spirit of the Father and of the Son. This ineffable Divinity, abiding, ever in itself, making all things new, creating, creating anew, sending, recalling, judging, delivering, this Trinity, I say, we know to be at once ineffable and inseparable.” Augustine, Serm. 52.2.
 Ayres, Nicaea and Its Legacy, 373.
 Ayres, Nicaea and Its Legacy, 374.
 Khaled Anatolios, Athanasius, The Early Church Fathers (London: Routledge, 2004), 142.
 Athanasius, De Decr. § 13. (All translations De Decretis from: Anatolios, Athanasius, 154.).
 Athanasius, De Decr. § 14.
 Athanasius, De Decr. § 14.
 “If he is not Son, let him be called a work. And let everything is designated of works be applied also to him. And let it not be said of him alone that he is Son and Word and Wisdom. And let it not be said of God himself that he is Father, but merely maker and creator of the things which he brings into being. And let the creature be Image and Expression of his creative will. In accord with them, let not God be of a generative nature, so that there may be no Word nor Wisdom nor any Image at all of his own essence. For if he is not Son, then neither is he Image. But if there is no Son, how then do you say that God is Creator, if indeed it is through the Word and in Wisdom that everything that is made comes to be and without which nothing comes to be, and yet, according to you, God does not possess that in which and through which he makes all things.” Athanasius, Or. 2.2. (All translations of Orations from: Anatolios, Athanasius, 89–90.).
 Athanasius, Or. 2.2. Anatolios, Athanasius, 90.
 Gregory of Nyssa, On the Holy Trinity.
 “The Father, the Son, and the Holy Spirit alike give sanctification, and life, and light, and comfort, and all similar graces. And let no one attribute the power of sanctification in a special sense to the Spirit, when he hears the Saviour in the Gospel saying to the Father concerning His disciples, “Father, sanctify them in Your name”.” Gregory of Nyssa, On the Holy Trinity.
 “Now the fact that there is no distinction in the operations we learn from the community of the attributes, but of the difference in respect of nature we find no clear proof, the identity of operations indicating rather, as we said, community of nature. If, then, Godhead is a name derived from operation, as we say that the operation of the Father, and the Son, and the Holy Spirit is one, so we say that the Godhead is one.” Gregory of Nyssa, On the Holy Trinity.
 Basil, Letter 189.6.