The doctrine of eternal generation and divine immutability seem incompatible at first glance. Can we coherently say that God is both unchanging and eternally generative? To unpack this apparent contradiction, we will briefly consider what is being affirmed by the doctrines of divine immutability and eternal generation.
Classic theology has confessed the doctrine of divine immutability in contemplation of the scriptural witness to the perfectly simple triune God who is life. These twin doctrinal affirmations, simplicity and aseity, speak of the utter indivisibility (Deut. 6:4) and constancy (1 Thess. 5:24) of our God who is the inexhaustible ground (Rom. 11:36) and wellspring of life (Ps. 36:9) in and of himself. The doctrine of divine immutability is interwoven with these perfections, affirming that God is– as uncreated being, but he does not change– as with created becoming.
Thomas Aquinas points the way here: God’s uncreated being, and thus changelessness, is not affirmed by means of speculation about the ontological superiority of stasis or immobility. That is, the vicissitudes of change are not abstractly judged to be beneath God, rather they evidence potential inherent within change itself, either to grow or to diminish. Yet, neither are true of the Christian God who is always everything that he is (Exod. 3:14). He is changeless because he actually possesses the fullness of life itself. Classically, God is actus purus, pure act. Contemplating God’s undivided life hastens us to confess with the scriptural witness: YHWH does not change (Mal. 3:6).
This understanding of divine immutability, which distinguishes uncreated being from creaturely becoming, helps orient us to some of the difficulties that we sense when predicating the language of “generation” to God. Isn’t “generation” a term of creaturely becoming and not one of uncreated being? If so, how can it be compatible with divine immutability? First, a word about the limits of human speech, then a threefold reflection on how honoring this might help in differentiating creaturely and divine generation.
Speaking of the Ineffable
When we venture to speak of Almighty God we come to hallowed ground. The classic tradition has been intensely self-reflective concerning creaturely speech about God’s inner life – especially of divine generation. Patristic theologians issued a range of warnings from Irenaeus urging the Gnostics not to speak impiously of the Son’s generation “as if they themselves had assisted at His birth,” to Hilary cautioning “in this case we, whose faculties can deal only with the visible and tangible things, are straining after the invisible, and striving to grasp the impalpable.” An acute awareness of the limits of creaturely speech, rooted in the absolute interval between Creator and creature, has caused theologians to give a chastened account of theological language. This spiritual posture of humility and analogical reserve is essential for wise speech about the Son’s procession in God’s inner life.
Following this patristic and medieval precedent, Herman Bavinck’s treatment of the Son’s generation seeks to honor the sheer difference between Creator and creature and is instructive for our question. Bavinck’s description of the Son’s generation wisely traverses the analogical interval between human and divine generation, laboring to speak rightly of the ineffable. He highlights three types of necessary distinctions between the Son’s generation and creaturely generation which help distinguish the two: (1) corporeal/incorporeal; (2) procreation/generation; (3) temporal/eternal. To say that the Son’s generation is spiritual is to mark the distinction between the incorporeal life of God and the corporeal existence of creation. Click To Tweet
The Son’s Generation is a Spiritual Act
The Son’s generation by the Father is spiritual. To say that the Son’s generation is spiritual is to mark the distinction between the incorporeal life of God and the corporeal existence of creation. Failing to recognize this dimension of the Son’s generation was part of the Arian objection to the doctrine of eternal generation in the fourth century. This objection reasoned that all generation must involve a separation and division between begetter and begotten. Accordingly, if the Son was truly generated by the Father, then this must alter the life of God, rendering him mutable. Athanasius reports Arius’ clever argument that God did not beget his Son as Valentinus pronounced that the offspring of the Father was an issue; nor as Manichæus taught that the offspring was a portion of the Father, one in essence (homoousios); or as Sabellius, dividing the Monad, speaks of a Son-and-Father; nor as Hieracas, of one torch from another, or as a lamp divided into two.
Arius sought to show that each of these approaches fall short by making God compound rather than simple, divisible rather than undivided, mutable rather than immutable, corporeal rather than incorporeal. This argumentative approach, associating Nicaea’s homoousios with heretical options, enabled Arius to deny its theological judgement. If the Son did issue forth from the Father, in such a way that the two shared the same nature (homoousios), then either there are two gods (Valentinus), or God is corporeal (Manichæus), or God is mutable (Sabellius), and thus God is not one (Hieracas) because the Monad is divided. Thus Arius set out to comprehensively and methodically remove all notions of generation other than creation from the divine will on the basis that all other conceptions would involve corporeality, change, or division within the one eternal Godhead—options which both Arius and his pro-Nicene opponents agreed were theologically untenable. The Arian argument demanded that it was impossible for God to be one and for both the Father and the Son to be that one God.
The pro-Nicene response to this, which Bavinck proffers, is to reply that while certainly this is the case with corporeal generation, yet the Son’s generation is an incorporeal act – spiritual and thus incapable of separation or division.
The Son’s Generation is an Internal Act
This leads to a second distinction Bavinck makes: The Son’s generation by the Father is a whole communication of essence. Again, the Arian controversy provides a helpful set of specifications here. As Athanasius defended the pro-Nicene teaching about the Son’s generation, he distinguish it from creaturely generation: “What is from the essence of the Father, and proper to Him, is entirely the Son; for it is all one to say that God is wholly participated, and that He begets.” Here he describes the Father-Son relation as “whole participation”—a phrase that functions in parallel with “begetting.” “Whole participation” indicates that the Son is not an offspring by means of participating in something external to the Father, but instead he is of the Father’s essence and thus “proper” (idios) to him. So Athanasius can say the divine essence is “entirely the Son” just as it is the entirely the Father. Thus for Athanasius, simplicity is not compromised by this; instead divine simplicity is re-imagined to include the Father-Son relation.
To grasp this by way of comparison consider the begetting of a creature. When a creature is begotten, it always involves separation and division of corporeal matter from begetter that is donated to the begotten. As such, creaturely generation always involves an outward movement from parent to child. However, because God is not composed of parts (he is simple and spiritual), his nature is neither divisible nor transitive. The only way in which God could truly be the Father of a Son by nature would be in a way internal to his own spiritual and indivisible life. Thus the scriptural attestation that God is the Father of his Son implies a “whole participation,” as Athanasius put it, from Father to Son within the divine life.
Again, note the careful distinction between created and uncreated that is employed here. The Son’s begetting is not an outward act (e.g. – procreation), but an internal act, according to God’s own nature (e.g. – generation). This distinction is concisely summarized in Nicaea’s “begotten not made.” The Son’s begetting is not an outward act (e.g. – procreation), but an internal act, according to God’s own nature (e.g. – generation). This distinction is concisely summarized in Nicaea’s “begotten not made.” Click To Tweet
The Son’s Generation is an Eternal Act
Finally, Bavinck’s third distinction: The Son’s generation by the Father is eternal. To speak of the Son’s generation as eternal, is to locate this act in God’s life and not within a created sequence of events. Again, Athanasius is instructive here as he argues that the Son’s generation must be understood with reference to eternity, which befits the perfection of the divine life, for although “it is proper to men to beget in time, from the imperfection of their nature, God’s offspring is eternal, for His nature is ever perfect.”
Why must this be so?
Because of God’s simple spiritual nature, divine generation is not like creaturely generation that is characterized by chronological difference between begetter and begotten. Instead, since God is incorporeal and indivisible, divine generation is internal not external. Correspondingly, whereas human generation necessarily involves a change in time, “no son” at one moment and “son” at the next, divine generation proclaims there is never a time when the Son is not the Son of the Father.
Bavinck remarks that a denial of the Son’s eternal generation makes God “changeable, robs him of his divine nature, deprives him of his eternal fatherhood, and leaves unexplained how we can properly call him ‘Father’ in time if the basis for calling him ‘Father’ is not eternally present in his nature.” Unless one confesses that God is by nature eternal Father of the Son, immutability itself is undermined. In this, eternal generation points to the natural fecundity of the divine life. Again Bavinck observes that as it is natural for a star to shine and for a well to spring forth water, so it is natural for the Father to generate the Son.
These are the very issues that were at stake in the Arian controversy, and they remain perennial matters of Christian concern. Reflecting again on the words of the Nicene Creed (381), classic Christian teaching has affirmed the Son is begotten of the Father “before all ages.” This language aims to specify an act that is not complete in the past, nor awaiting completion in the future, but is temporally incommensurate and according to the perfection of God’s nature.
Tracing the full logic presented here: God is spirit, standing outside of the physical, and thus the temporal, order. The quality of temporal existence only applies in the realm of creaturely becoming, not of divine being. And, because the Father and Son (and Spirit) are incorporeal and immutable, the relations that exist between them are necessarily eternal. Classic theology, exemplified by Nicaea, has therefore understood eternal generation as a mode of divine perfection and not as a threat to it.
By affirming the spiritual, internal, and eternal nature of the Son’s generation, it is thereby distinguished from creaturely generation allowing this doctrine to coherently stand together with the doctrine of divine immutability. God’s incommunicable perfections: simplicity, immutability, and aseity are not challenged but instead explicated by reflection on the eternal relations of Father, Son, and Spirit. The perfectly simple God is triune– an unchanging fountain of life in and of himself.
 Aquinas, Summa Theologiae1a. 2-4.
 Irenaeus, Against Heresies2.28.5-6 (ANF1:401).
 Hilary of Poitiers, On the TrinityIII.18 (NPNF29:67).
 Bavinck, Reformed Dogmatics: 2 (309-310). Bavinck writes of generation as (1) spiritual; (2) within the divine being; and (3) eternal. Here I’ve rephrased this and paired them his categories with their analogical counterparts in creation.
 Athanasius de Synodis 16 (NPNF Series 2, 4:458).
 Weinandy, Athanasius: A Theological Introduction, 54.
 Athanasius Contra Arianos 1.16.
 Athanasius C.Ar.1.14.
 Bavinck, Reformed Dogmatics: 2 (310).
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