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Incarnation or Metamorphosis?

Understanding the Simplicity of God in Light of the Incarnation

We live in an exciting time of theological retrieval. Our era is marked by a captivating journey of rediscovering ancient truths. For some, this odyssey induces fear—an apprehension rooted in reluctance to admit past errors or a resistance to reevaluate entrenched beliefs. On the other hand, more adventurous minds grapple with the challenge of applying age-old wisdom to contemporary questions.

Divine simplicity and the incarnation are compatible because the incarnation terminates on the person of the Son rather than the nature. Click To Tweet Specifically, the classical Christian doctrine of divine simplicity has undergone a riveting revival; this pillar of classical Christian theism has been among many treasures rediscovered from our rich Christian heritage. Yet, not everyone welcomes its return with open arms. Certain theologians ask, “How can simplicity be true in light of the incarnation? If God is not composed, how can God the Son have two distinct natures? Doesn’t the hypostatic union entail some amount of composition or change in God?”[1] While I wouldn’t fault well-meaning laymen for such questions, it is alarming that scholars who have written volumes on God, the Trinity, and the incarnation would posit such a critique. In reality, it is no wonder that the former are ill-equipped to harmonize such doctrines when the latter have been blind guides. They say where there is a mist in the pulpit, there is a fog in the pew. In this case, the mist is in the library, and has ruined all the books.

In response to this conundrum, we are faced with offering some much-needed clarity: divine simplicity and the incarnation are compatible because the incarnation terminates on the person of the Son rather than the nature. In order to substantiate this claim and cut through the alleged Gordian knot, we will first look at the claims of divine simplicity, then consider the claims of the incarnation, and, finally, seek to harmonize these vital doctrines.

Divine Simplicity

Ironically, the idea that there must be reconciliation between the doctrines of divine simplicity and the incarnation is but a category error. Simplicity concerns the divine nature whereas the incarnation concerns the terminus of the Triune God upon the second person of the Godhead in the assumption of a human nature.

When we talk about simplicity in relation to God, we do not mean that God is easy, basic, or unsophisticated. Instead, we mean that God is not made up of different parts. It is not as if God was a mixture of some goodness, a bit of mercy, a dash of power, a pinch of justice, and so on, like a recipe. God is all of these things and more, all the time. Every aspect of God is, in reality, not even an “aspect” at all. God’s attributes are all the same as His essence; they cannot be separated or changed without affecting who God is.

Some people mistakenly think that one aspect of God, like love, is more important than others. The doctrine of divine simplicity helps us avoid such errors. In everything else except God, there is a difference between a thing’s essence (what makes it what it is) and its existence (that it exists). Simplicity, however, teaches that God does not have this distinction; everything about God is essential to who He is.

To get a bit technical, this means God has no accidental properties. Whereas saying a man who has two legs and two arms could lose one limb without changing the essential truth of being a man, God does not have parts that can be removed without changing who He is. In simpler terms, everything that makes God “God” is crucial and cannot be taken away or altered without changing God Himself. [2]

There is nothing in God that is less than God, and if anything were missing in God, He would cease to be God. When it comes to the divine nature, God’s justice is His eternity, is His love, is His holiness, and so on. What we refer to as “attributes” are but the manifestation of the divine nature as understood by creation. With that said, the doctrine of simplicity is central to helping orient our thoughts about God. Since the Bible is not a systematic theology handbook, we need to make sure that all the data that we gather from God’s Word to formulate conclusions provides a harmonious body of truth. After all, the data of Scripture is self-consistent because God is self-consistent.

With that in mind, you may wonder which biblical texts support the doctrine of simplicity. This truth is not contained in a solitary text. It is a derived doctrine; it is a necessary doctrine based on the truths of other doctrines, and it is necessary for faithful, exegetical harmony. Still, some texts work as establishing principles by which we can deduce the doctrine of simplicity. This truth is similar to the Trinity—it is the necessary implication of a great number of texts.

For example, texts that depict God as not deriving an aspect of Himself from another fall into this category. God does not receive His life from another; He is independent in His being. To be Himself, He cannot depend on what is not Himself. An existence that is composed of parts is an existence that is dependent on those parts, because parts give actuality to the whole. Scripture teaches, however, that no one gives to God. For example, when Scripture speaks of God receiving nothing from man, it often lists a part: God receives no wisdom from man, no counsel from man, and no glory from man that He does not already possess. Since God is self-existent, and does not receive definition or existence from another, He therefore cannot be composed of parts.

We see this a few times in Job. Job 22:3 reads, “Is there any pleasure to the Almighty if you are righteous, / Or profit if you make your ways perfect?” Even if you made yourself perfect it would not profit God because He is not lacking anything. Continuing to Job 35:7 we see, “If you are righteous, what do you give to Him, / Or what does He receive from your hand?” Even a perfectly righteous person could offer no gain to God.

Christian theologians have consistently affirmed that the Threeness of God—that God is Father, Son, and Spirit—refers to the distinctions of the persons subsisting in the divine essence, not divisions in God. So, there are three distinct persons, not three divisions of essence that when put together make up God. God is not one-third Father, one-third Son, and one-third Spirit. While the persons may be distinct, this does not mean there are divisions (or parts), which is the conclusion of all historic Trinitarian councils and the manifest witness of the Oneness of God (Deut. 6:4). However, how do we reconcile this with the incarnation? Again, the answer comes in properly understanding the different categories of “person” and “nature.”

What is a Person?

In order to understand our next claim regarding the incarnation we have to ask, “Who is incarnate?” And by asking “who” we are immediately pressed to define what “who” means. Simply put, it is a statement of person. If you were to ask a general audience of “Christian” pastors, “What is a person?” you would likely get a number of opinions and definitions. We should be concerned that we get a variety of answers instead of one clear definition. History has shown that the Christian faith hinges on the definitions of “person” and “nature.” Click To Tweet

In today’s rapidly changing world, in which many things are fluid and adaptable, some argue that the concept of having fixed definitions is becoming outdated. This sentiment is especially true when it comes to complex and nuanced concepts like “God,” “man,” “person,” and “nature.” These terms carry a lot of weight and can be interpreted in various ways depending on the individual and the context.

However, having clear definitions for these terms is still important. Precise definitions help us have more meaningful conversations and avoid misunderstandings. They can also provide a foundation for critical thinking and reasoned arguments.

Therefore, it is essential to carefully consider and define these terms, even if the definitions evolve over time. For example, Theodore Beza wrote, “This was why, long ago, the Greek terms οὐσία (ousia) and ὑπόστασις (hypostasis) were adopted against Sabellius Afer, who confused the persons with the essence, and against Samosatenus of Antioch, who destroyed the Son’s divine nature.”[3] History has shown that the Christian faith hinges on the definitions of “person” and “nature.”

Admittedly, since these terms arise from philosophy, we have to have a grasp of metaphysics in order to employ them. Our faithful usage of these terms requires studying metaphysics. While some may bristle at such a suggestion, it should be recognized that the question is not whether we should study the Bible alone (apart from metaphysics), but , what kind of metaphysics does the Bible require us to believe in.[4] Because the Bible describes God in categories such as three persons (Matt. 28:19) in one nature (Deut. 6:4), it requires us to understand person and nature. Therefore, whether they realize it or not, acknowledge it or not, all Christian theologians utilize metaphysics. The Bible explains person as an active entity, a “who,” and nature as the means by which a person acts, the “what.” Natures, unlike persons, do not act or have experiences; they are the tools by which a person acts and has experiences. The idea of person as “who” and nature as “what” has been core to Christian thought for centuries.

One important definition of “person” comes from Boethius. Boethius defines a “person” as “an individual substance of a rational nature.”[5] This definition is crucial for understanding core Christian beliefs like the Trinity and the incarnation.

Furthermore, Boethius’ definition taught that “nature” is the foundation of “person” and that they cannot be separated. He argued and that both natures and substances are necessary for a person to exist.[6] Boethius distinguished different types of substances, including rational and irrational, living and non-living. Ultimately, he concluded that “person cannot be predicated of bodies which have no life (a stone), not yet of living things which lack sense (a tree), but we say there is a person of a man, of a God, of an angel.”[7]

In simpler terms, according to Boethius, a person is a combination of unique characteristics (their individual substance) and the ability to reason (rational nature). This definition is important because it helps clarify the concept of personhood in light of both the hypostatic union and the Trinity.

Built into the definition of person is an affirmation of divine simplicity. For example, if the distinctions between persons in God (Father: unbegotten, Son: begotten, Spirit: proceeding) were divisions, such that “Father” is one part, “Son” another part, and “Spirit” yet another part, then God is three parts that when fashioned together equal God. The obvious problem is that this misunderstanding creates three gods or three persons who are all sub-God.

The definition of a person, as a “who,” or better yet, an individual substance of a rational nature, leads us to our next question.

What is the Incarnation?

In continuing to address the objection that simplicity and the incarnation are contradictory, we should ask, “What precisely is the incarnation?” Simply put, in the incarnation it is not the divine nature assuming a human nature into union with itself, but rather it is a particular divine person who assumes that second nature into union with Himself. Everything that makes God “God” is crucial and cannot be taken away or altered without changing God Himself. Click To Tweet

The Son does not have a human person, rather He assumes a human nature. It is not the divine nature (in the absolute sense) that assumes a human nature. In the incarnation, God creates the human nature of which the second person of the Godhead assumes in union with Himself. The humanity of our Lord does not have a unique existence independent of the Son, which is commonly referred to as the assumption of a “unique mode of existence” not the taking on of an independent nature that self-existed. That is to say, the humanity of Jesus did not exist on its own apart from the incarnation (as that would be Apollinarianism).

It seems, then, that a proper view of divine simplicity safeguards a proper view of the incarnation, for if something can happen to God in order to be incarnate, God is not immutably simple. If that were the case, we would not have an incarnation of God at all, but rather a metamorphosis into some third thing.

How Does the Incarnation Happen, and to Whom?

In order to answer this question, we can simply say, 1) The works of the Trinity are inseparable, 2) Those works can be understood in their principle and their terminus, and 3) The act of the incarnation is Triune in principle and terminates on the person of the Son alone, not the Father and/or Spirit. Though the Son alone assumed a human nature, all three persons of the Trinity acting in unison brought about that reality. The doctrine of inseparable operations (opera Trinitatis ad extra indivisa sunt) offers invaluable aid here, preventing us from inadvertently presenting the incarnation of the Son as the subordination of deity.[9]

There can be a distinction in divine action between the beginning of a given ad extra work (principium) and its end (terminus). In that way, the Father can be attributed with the act of the incarnation, same as with the Son and Spirit, and yet the ad extra work can be expressed regarding any of the persons without removing causal power from any of the persons. In other words, to say that any given person of the Trinity caused the incarnation is not to say that the other persons did not.

The principium of the ad extra work belongs to the divine nature (expressed by inseparable operations) and the terminus (expressed by appropriations) to a specific person of the Godhead. Applying this to the incarnation, the Triune God incarnated (principium) the Son such that only the Son is incarnated (terminus).

We know the terminus of the act of the incarnation was upon the Son, because Scripture never claims that the Father or Spirit became incarnate. Yet, the Son was not passive in the incarnation—as some may wrongly suppose. Rather, the Son (as God) was active in His own incarnation (Phil. 2:5–7).[10] Thomas Aquinas helpfully explains how the incarnation takes place “according to which something distinct is said of the divine persons.”[11] The incarnation is not the incarnation of the divine essence but only of the person of the Son, one personal mode of subsisting. Therefore, there are not three incarnations, but one incarnation of the Son by the triune God.[12]

In the incarnation we can see the Trinitarian members operate in a manner fitting to their respective modes of subsisting. The Father sent the Son to be incarnate, the Son is the one who became flesh, and the Son’s conception was by the power of the Holy Spirit. Therefore, the unity of the Godhead is preserved, even when God’s ad extra work is more particularly attributed to one given person.

How Does the Hypostatic Union Language Help?

The second keystone aspect of the incarnation is how Christ’s two natures—human and divine—exist united in one person. This doctrine is commonly referred to as the hypostatic union. The ecumenical Council of Chalcedon in AD 451 affirmed that Jesus was “truly God and truly man,” and that the two natures of Christ are inseparably united, yet without mixture, confusion, or division, each nature retaining its own attributes.[13] According to this council, the human nature does not have a personality or subsistence of its own. In becoming a man, the Son assumed a second nature, not a second “person.” The two natures are conjoined together in the one person.

It is crucial to understand both of these important elements of the hypostatic union—the assumption of human nature by the divine Son and the unity of both natures in one person. The fullness of God dwelling in human form is God’s assumption of a human nature.[14] It is the indescribable divine act whereby the second person of the Godhead, the Son of God, took on humanity into subsistence with Himself (Col. 2:9; Phil. 2:7).

It is important to note that none of the following is true of the Godhead: It was not born of a virgin, was not the seed of David, was not made in our likeness, made flesh, made of a woman, nor changed into flesh. Divinity was in no way changed when Christ took on flesh.[15] Furthermore, neither the Father nor the Spirit assumed a human nature to their persons; the Son alone is the recipient of conjoined flesh. “The eternal Son assumes a nature—not a person—in the incarnation

The eternal Son assumed a human nature; the human nature never assumed the divinity of Christ. “Assumption is unto personality; it is that act whereby the Son of God and our nature became one person. Union is an act of relation of the natures subsisting in that one person.”[17] He is not two persons, self-existing and becoming one. That statement is in and of itself a contradiction; Christ’s human nature does not have its own person apart from the divine person.


In the grand tapestry of theological inquiry, few questions loom larger than the enigma of the incarnation: How can the majestic, unchanging God of simplicity be clothed in mortal flesh? Modern audiences are lost to answer this conundrum without making a Frankenstein God.

Yet, amidst the labyrinth of theological confusion that ravishes many modern thinkers, the historic doctrine of divine simplicity emerges as a beacon of clarity—a resplendent solution to the age-old conundrum. In its luminous essence, we find the key to reconciling the infinite with the finite, the transcendent with the immanent.

By embracing the truth that God’s nature transcends composition, we unlock the door to a deeper understanding of the incarnation. Through a precise comprehension of nature and person, we boldly affirm the simultaneous simplicity of the divine nature of the Son and the complexity of His human nature in the incarnation.

In this pivotal moment of theological renaissance, let us heed the clarion call to return to the bedrock of our Christian faith. Let us cast off the allure of novelty and the fetters of errant teachings that seek to lead us astray. By embracing the timeless truths that have shaped the ages, we discover a path illuminated by the radiant splendor of divine revelation, and as we journey forward, may our hearts be steadfast, our minds discerning, and our worship fervent. In knowing the Triune God and the incarnate Son, we find the true essence of Christian faith—a faith rooted in the eternal verities that transcend the ebb and flow of modern human history.


[1] For example, “[If] we say that God only appears to change in these contexts, must we also say that God only appears to enter time, that the Son of God only appeared to become man (that is the textbook definition of Docetism), that he only appeared to die on the cross and rise again? . . . It implies that Jesus did not ‘literally’ become man, suffer, and die for us. He was not literally born of a virgin. . . . why is [Scripture] not anthropomorphic when it speaks of God’s changelessness? Why should we believe literally that God is changeless, but not that God literally became flesh in Jesus?” John Frame, “Scholasticism for Evangelicals: Thoughts on All That Is in God by James Dolezal,” November 25, 2017, Even more overt, “A student inquires if the incarnation requires a change in God, William Lane Craig responds, ‘he keeps all those attributes but he does assume a human nature in addition to the Divine nature he already has.’ He asks isn’t that a change? I am inclined to say yes, but I don’t see that as problematic. I don’t see that as contradicting any of these respects in which the Bible says God is immutable. The second person of the Trinity changed in the sense that at one time he did not have a human nature, and at another time he did have a human nature. To me that is just unobjectionable. I don’t see any problem with that biblically or theologically.” “Doctrine of God (Part 9): God’s Immutability: Reasonable Faith,” Defenders: 3 | Reasonable Faith, accessed March 14, 2024,

[2] Portions of this were adapted with permission from, Peter Sammons, The Forgotten Attributes of God: God’s Nature and Why it Matters (Fort Washington, PA: CLC Publications, 2023), 65–75. This laymen treatment is intended to be an introduction to classical theism and to function as a primer for more important works such as: James Dolezal, All That Is In God: Evangelical Theology and the Challenge of Classical Christian Theism (Grand Rapids: Reformation Heritage Books, 2017) and Steven J. Duby, Divine Simplicity: A Dogmatic Account (Edinburgh: T&T Clark, 2018).

[3] Theodore Beza, The Unity of the Divine Essence and the Three Persons Subsisting in It, Against the Arians’ Homoiousios, Thesis V, OPC, accessed March 14, 2024,,is%20unbegotten%2C%20begetting%20the%20Son. Also, Richard Muller wrote, “In brief, all of the major trinitarian heresies involved difficulties with the term’s ‘substance’ and ‘person’, specifically, a failure to distinguish them properly.” Richard A. Muller, Post-Reformation Reformed Dogmatics, Vol. 4,: The Triunity of God (Grand Rapids: Baker, 2003), 31.

[4] Mike Riccardi, “Pursuing Unity on Triunity,” Pursuing Unity on Triunity | Shepherds Conference | Grace Community Church, accessed March 14, 2024,

[5] Boethius, Liber de Persona et Duabus Naturis, ch. 3; Patrologia Latina, ed. J. P. Migne, 271 v., indexes 4 v. [Paris 1878–90] 64:1345. Also, in a more accessible English version, Boethius, “Contra Eutychen,” in Boethius: Theological Tractates, trans. H.F Stewart, E.K Rand, and S.J Tester, (Cambridge, MA: Loeb Classical Library, 1978), 85.

[6] Ibid. For helpful sources see: Roberto Pinzani, ed., The Problem of Universals from Boethius to John of Salisbury, Brill’s Studies in Intellectual History, volume 282 (Leiden: Brill, 2018).

[7] Boethius, “Contra Eutychen,” The Theological Tractates, 85.

[8] Francis Turretin, Institutes of Elenctic Theology.Vol. 2, trans. George Musgrave Giger, ed. James T. Dennison (Phillipsburg: P&R, 1994), 2:305. He writes, “Although the divine nature may properly be said to have been incarnated in the Son, it does not follow that the whole Trinity became incarnate…And the fathers hold this, who affirm that the divine nature is incarnate (to wit, in one of the hypostases [en mia hypostaseon] and in the hypostasis of the Word [en hypostasei logou])” (Vol 2.Topic 13.Question 4. Section VII). What Turretin acknowledges here is that the Father and the Spirit remain unembodied, and when examining the divine essence in its purest form (absolutely), it is evident that it does not take on human form. However, the divine essence does take on human form through the Son.

[9] Material in this section has been adapted from Peter Sammons, “When Distinction Becomes Separation: The Doctrine of Inseparable Operations,” The Master’s Seminary Journal 33.1 (Spring 2022): 75–97. For more on the doctrine of inseparable operations, see: Adonis Vidu, The Same God Who Works All Things (Grand Rapids: Eerdmans, 2021); Jacob S. Trotter, “‘This Old Rule Should Be Remembered’: Three Historical Arguments for Inseparable Operations,” Journal of Classical Theology 2 (2023) 69–90. For helpful works on the missions and why we should not collapse those back onto the modes of origin see: Barrett, Simply Trinity: The Unmanipulated Father, Son, and Spirit, 287–315; Scott R. Swain, The Trinity: An Introduction (Short Studies in Systematic Theology) (Wheaton: Crossway, 2020).

[10] Mike Riccardi, “Veiled in Flesh the Godhead See: A Study of the Kenosis of Christ,” The Master’s Seminary Journal 30/1 (Spring 2019): 103–127; also, Mike Riccardi, “He Emptied Himself: The Kenosis,” in High King of Heaven, ed. John MacArthur (Chicago: Moody Press, 2018), 107–17.

[11] Aquinas, Summa Theologica, 3a.3.4sed contra.

[12] All three persons are active in the single work of the incarnation because of the doctrine of ISO (inseparable operations). Aquinas helpfully states, “The three persons caused the human nature to be united to the one person, the Son [see Luke 1:35; Heb 10:5]” (Summa Theologica., 3a.3.4resp).

[13] The purpose of this council was to refute errors regarding the incarnation; see the definition of faith for the council of Chalcedon: The Seven Ecumenical Councils, NPNF2, eds. Alexander Roberts, James Donaldson, Philip Schaff, and Henry Wace (1900; repr., Buffalo, NY: Hendrickson, 1994), 14:262–65. “For it opposes those who would rend the mystery of the dispensation into a Duad of Sons; it repels from the sacred assembly those who dare to say that the Godhead of the Only Begotten is capable of suffering; it resists those who imagine a mixture or confusion of the two natures of Christ; it drives away those who fancy his form of a servant is of an heavenly or some substance other than that which was taken of us, and it anathematizes those who foolishly talk of two natures of our Lord before the union, conceiving that after the union there was only one” (14:264).

[14] For more on this, see: James E. Dolezal, “The Word’s Terminative Assumption of a Human Nature,” Nova et Vetera. English Edition, 20/1 (2022):133–57.

[15] For more information see Steven J. Duby, Jesus and the God of Classical Theism: Biblical Christology in Light of the Doctrine of God (Grand Rapids: Baker Academic, 2023).

[16] W. E. Best, The Impeccable Christ (Grand Rapids: Sovereign Grace, 1971), 29.

[17] John Owen, On the Person of Christ, The Complete Works of John Owen, ed. William H. Goold (repr., Carlisle, PA: Banner of Truth Trust, 2008), 1:226.

Peter Sammons

Peter Sammons (PhD, The Master’s Seminary) is the author of Reprobation and God’s Sovereignty: Redeeming a Biblical Doctrine (Kregel, 2022).

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