Chapter 14

The Hypostatic Union, Dyothelitism, and the Communication of Attributes

Introduction: The Architecture of the Incarnation

We have now arrived at one of the most important chapters in this entire book. In the previous chapters of Part III, we traced the development of Christological orthodoxy from Nicaea to Constantinople III. We watched the early church wrestle with who Jesus really is — fully God, fully man, one Person, two natures. We saw how Apollinarianism was condemned for denying Christ a human rational soul, and how the monothelites were rejected for denying Christ a genuine human will. Each of these battles added another layer to the church's understanding of the mystery of the Incarnation.

Now, in this chapter, we need to pull all of those threads together. We need to look carefully at the three great doctrines that form the core architectural framework of orthodox Christology: the hypostatic union, dyothelitism, and the communicatio idiomatum (the communication of attributes). These three doctrines are not isolated ideas floating around on their own. They are deeply connected to one another. Together, they form a single, magnificent, and logically coherent picture of who Jesus Christ is — one divine Person who possesses two complete natures, two wills, and two sets of natural properties, all united in one personal subject.

And here is the thesis I want to argue in this chapter: each of these three doctrines — the hypostatic union, dyothelitism, and the communicatio idiomatum — presupposes and requires that Christ's human nature includes an immaterial human soul. These are not doctrines that sit comfortably alongside physicalism. They are doctrines that demand a dualist understanding of human nature — one that recognizes the soul as a genuine, immaterial component of what it means to be human. When we understand what the hypostatic union actually claims, when we see what dyothelitism actually requires, and when we grasp how the communication of attributes actually works, we will see that physicalism — the denial that human beings have immaterial souls — is simply incapable of sustaining these essential doctrines.

I believe this chapter addresses the very heart of Christological metaphysics. The framework we lay out here is the foundation upon which everything else in the rest of this book will stand. So let us take our time, define our terms carefully, and trace the argument step by step.

I. The Hypostatic Union: One Person, Two Natures

A. What Is the Hypostatic Union?

The hypostatic union is, at its most basic level, the teaching that Jesus Christ is one divine Person who possesses two complete natures — a divine nature and a human nature — united together without confusion, without change, without division, and without separation. The word "hypostatic" comes from the Greek word hypostasis (ὑπόστασις), which means something like "that which stands under" — a concrete, individual reality, a specific "someone." When we say the union is "hypostatic," we mean that the two natures are united in one hypostasis — one concrete, individual Person.¹

This is the doctrine that the Council of Chalcedon formally defined in 451 AD. The Chalcedonian Definition declared that Christ is to be "acknowledged in two natures, without confusion, without change, without division, without separation," and that the distinction of the natures is "in no way abolished by the union, but rather the property of each nature is preserved, and concurs in one person and one subsistence."² These four famous adverbs — in Greek, asynchytōs (ἀσυγχύτως), atreptōs (ἀτρέπτως), adiairetōs (ἀδιαιρέτως), and achōristōs (ἀχωρίστως) — act as boundary markers. They tell us what the union is not, and in doing so, they preserve the mystery while excluding all of the major heresies.

Let me explain each adverb briefly. "Without confusion" (asynchytōs) means that the two natures do not blend into some kind of hybrid. Jesus is not a mixture of God and man — some kind of half-God, half-human. The divine nature stays divine; the human nature stays human. "Without change" (atreptōs) means that neither nature is altered by the union. The divine nature is not changed into something less than fully divine, and the human nature is not changed into something more than human. "Without division" (adiairetōs) means that the two natures are not separated into two persons. Jesus is not two people sharing one body. He is one Person. And "without separation" (achōristōs) means that the natures are never pulled apart — they remain united. This last adverb will become critically important when we turn to the question of what happens at the death of Christ, as we will explore in Chapters 21 and 22.³

B. Person and Nature: The "Who" and the "What"

To understand the hypostatic union, we need to be very clear about the distinction between "person" and "nature." This distinction is one of the most important conceptual achievements in the entire history of Christian theology. It was hammered out over centuries of debate, and getting it right is absolutely essential for understanding who Jesus is.

A nature answers the question "What is it?" It tells you what kind of thing something is. My nature is human — I have a human body and a human soul, with all the capacities that come along with being human: the ability to think, feel, choose, grow, suffer, and so on. God's nature is divine — He possesses omniscience, omnipotence, omnipresence, eternity, and all the other attributes that belong to deity. A nature, then, is the set of essential characteristics that make something what it is.⁴

A person (or hypostasis) answers the question "Who is it?" A person is the concrete, individual subject — the "I" — who acts, thinks, wills, and experiences. It is the person who is the subject of predication. That is a technical way of saying: it is the person about whom we make statements. We do not say "Jesus' divine nature walked on water and His human nature ate fish." We say "Jesus walked on water" and "Jesus ate fish." It is the one Person — the Son of God — who does both. The Person is the doer. The natures are the capacities through which the Person acts.⁵

Michael Wilkinson captures this beautifully in his concept of "Chalcedonian anthropology." He argues that the Chalcedonian Definition presents a clear person-nature ontology: the divine person of the Son is the ontological subject — the "I" — of both His divine and human natures. As Wilkinson puts it, the person of the Son, as the second hypostasis of the Trinity, "is the ultimate acting subject of the incarnation, which was a divine act of the divine person of the Son in which he became a man by creating and subsisting in a human nature."⁶ The person of the Son did not exist alongside a second person called "Christ." Rather, the Word became incarnate as one Person in an additional nature.

Let me try a simple illustration. Think about a person who is both a parent and a professional. Maria is a mother and a physician. Those are two different roles, two different sets of activities and responsibilities. But there is only one Maria. It is the same Maria who reads bedtime stories to her children and who performs surgery at the hospital. The roles do not divide her into two people. Now, this analogy breaks down in an important way: being a parent and being a physician are roles, not natures. They are things Maria does, not what Maria is. Christ's two natures are not roles He plays — they are ontological realities, real aspects of what He is. But the analogy still helps us see the basic point: one subject can be the bearer of two different sets of properties without being divided into two subjects.⁷

C. The Person of the Son as the Subject of the Union

Who, exactly, is the Person in the hypostatic union? It is not a new person who came into existence at the Incarnation. It is the eternal Son of God — the second Person of the Holy Trinity — who has existed from all eternity with the Father and the Holy Spirit. At the Incarnation, this eternal divine Person assumed a human nature — that is, He took on a human body and a human soul. He did not cease to be what He already was (God); He became something He had not previously been (man). As the church fathers liked to say, the Incarnation was an act of addition, not subtraction. The Son added a human nature to His eternal divine nature without losing or changing anything about His divinity.⁸

This point is critical for our purposes. The Person who unites the two natures is not a human person. He is a divine Person. The human nature of Christ does not have its own separate personal center — it has no independent "I" of its own. Instead, it finds its personal identity in the Person of the Son. This is what the later theological tradition called enhypostasia — the teaching that Christ's human nature subsists "in" the Person of the Son. It does not exist on its own as a free-standing individual; it exists as the human nature of the Son. The full treatment of anhypostasia and enhypostasia is given in Chapter 19, but the basic idea is straightforward: the Son is the Person who owns both natures.⁹

Constantinople II (553) made this explicit. As Wilkinson documents, the council's canons "repeatedly interpret the incarnation as an act of the second hypostasis of the Trinity, in which he was 'made man' or 'made flesh.'" The council declared that "one of the Holy Trinity has been made man" — clarifying beyond any possible doubt that the one hypostasis of Chalcedon is, first and foremost, the Second Person of the Trinity.¹⁰

D. Pawl's Philosophical Defense of the Hypostatic Union

Is the hypostatic union logically coherent? Many critics have charged that the idea of one Person with two natures is logically contradictory — like saying something is a square circle. Timothy Pawl, in his rigorous and important book In Defense of Conciliar Christology, takes this challenge head-on. Using the tools of analytic philosophy — predicate logic, modal logic, and careful conceptual analysis — Pawl sets out to show that the conciliar definitions are not self-contradictory.¹¹

Pawl's approach is modest but powerful. He does not try to explain the Incarnation — he freely acknowledges that the councils themselves declared the hypostatic union to be "ineffable," that is, ultimately beyond full human comprehension.¹² What Pawl does instead is show that the conciliar claims are logically consistent. They do not produce actual contradictions. The apparent contradictions — like saying Christ is both omniscient and limited in knowledge, both immortal and mortal — can be resolved once we understand the metaphysical structure of the Person-nature framework.

Pawl identifies six necessary conditions that any viable model of the Incarnation must meet, drawn from the conciliar texts. Among them: (1) There must be one person, two natures, and two wills. (2) Christ's human nature must be the same type of thing as your or my concrete human nature. (3) Christ's human nature must have a body and a soul. (4) The soul must be the same type of thing as your or my soul. (5) The hypostatic union must remain ineffable. (6) The union must leave the proper characters of both natures intact.¹³

Notice condition three: Christ's human nature must have a body and a soul. This is not something Pawl imports from outside the conciliar texts. It comes directly from the councils themselves. As Pawl notes, any view that denies the existence of a human soul in Christ, or that identifies Christ's soul with the divine Logos, is "a view inconsistent with Conciliar Christology."¹⁴ The soul is non-negotiable.

E. The Metaphysical Structure of the Hypostatic Union: Dualism vs. Physicalism

Now we come to one of the most important questions for this book: what does the hypostatic union look like on dualism versus physicalism?

On substance dualism — the view I am defending — the Son is united to a human nature that consists of two components: a material body and an immaterial soul. This body-soul composite is what the councils meant by a "complete human nature." The Chalcedonian Definition explicitly states that Christ is "truly man of a rational soul (ek psychēs logikēs, ἐκ ψυχῆς λογικῆς) and a body."¹⁵ The rational soul is not an optional add-on. It is a constitutive element of Christ's human nature as the councils defined it.

On dualism, the soul provides something immensely important for the hypostatic union: it provides a continuous, immaterial bearer of the human nature even when the body dies. When Christ died on the cross, His body was placed in the tomb. But His soul — His immaterial, rational soul — survived death. The Son remained united to both the soul and the body. The soul went to the realm of the dead (as the Apostles' Creed affirms: "He descended to the dead"). The body lay in the tomb. Both components of the human nature remained united to the Person of the Son throughout the three days between crucifixion and resurrection — the triduum mortis. The Incarnation was not interrupted. "Without separation" was maintained.¹⁶

On physicalism, the picture is radically different — and deeply problematic. If physicalism is true, then Christ's human nature is His physical body. There is no immaterial soul. When the body died, there was nothing left of the human nature. The Son was united to — what? A corpse? Dead biological matter? A corpse is not a human nature in any meaningful sense. Dead tissue does not think, will, feel, or act. It is not a rational agent. It is not alive. On physicalism, when Jesus died, His human nature simply ceased to function. There was nothing of it that survived. For approximately thirty-six to forty hours, the Second Person of the Trinity was not incarnate. The Incarnation had a gap.

This is devastating. It contradicts Chalcedon's "without separation." It means the hypostatic union was broken at the cross. And if the hypostatic union was broken, then the Incarnation was temporary, not permanent. I will develop this argument fully in Chapters 21 and 22, but I want the reader to see the setup here: the hypostatic union, as defined by the councils, simply cannot survive on physicalist assumptions. The soul is not a luxury. It is a structural necessity.¹⁷

F. The Concrete Nature View

There is one more important piece of the hypostatic union puzzle that we need to address here. What exactly is a "nature"? Philosophers and theologians have debated this for centuries, and the answer matters enormously for how we understand the Incarnation.

Broadly speaking, there are two views: the abstract nature view and the concrete nature view. On the abstract nature view, Christ's human nature is a set of properties — "humanness" in the abstract, the property of being human. On the concrete nature view, Christ's human nature is a concrete particular — a specific, individual body-soul composite, a real flesh-and-blood (and soul) entity.¹⁸

I follow the concrete nature view, as do Pawl, Loke, Crisp, and the mainstream of the tradition. There are good reasons for this. First, the conciliar texts consistently speak of Christ's human nature in concrete terms — "flesh animated by a rational soul," a body born of Mary, flesh that suffered and died. This is the language of a concrete particular, not an abstract property. Second, the abstract nature view faces a serious difficulty with dyothelitism: if the human nature is just a set of properties, where does the human will come from? A property does not will anything. Only a concrete entity — one with a rational soul — can will. Third, as Oliver Crisp has argued, the concrete nature view fits more naturally with the mainstream patristic and medieval tradition.¹⁹

On the concrete nature view, the Son at the Incarnation assumed a concrete, individual human nature — a real human body united to a real human soul. This body-soul composite is "Christ's Human Nature," or CHN, as Pawl calls it, following Thomas Flint.²⁰ It is not humanity in general; it is a particular, concrete instance of humanity. And because it is a concrete particular — a body-soul composite — it requires both a body and a soul. Remove the soul, and you no longer have a concrete human nature. You have a body without a soul — which is, by definition, a corpse. The full treatment of the concrete versus abstract nature debate is reserved for Chapter 19, but the basic point should be clear here: on the concrete nature view that the councils presuppose, a human nature without a soul is no human nature at all.

II. Dyothelitism: Two Wills in One Person

A. What Is Dyothelitism?

Dyothelitism — from the Greek dyo (δύο, "two") and thelēsis (θέλησις, "will") — is the teaching that Christ has two natural wills: a divine will and a human will. This doctrine was defined at the Third Council of Constantinople (681 AD) after a long and often bitter struggle against monothelitism — the view that Christ has only one will (the divine will).²¹

The council declared:

"We likewise declare that in him are two natural wills and two natural operations indivisibly, inconvertibly, inseparably, inconfusedly, according to the teaching of the holy Fathers. And these two natural wills are not contrary the one to the other — God forbid! — but his human will follows, and that not as resisting and reluctant, but rather as subject to his divine and omnipotent will."²²

Notice several things about this definition. First, the council uses the same four adverbs that Chalcedon used for the two natures — indivisibly, inconvertibly, inseparably, inconfusedly — and applies them now to the two wills. Just as the natures are united without confusion or separation, so too the wills operate in harmony without conflict or merger. Second, the council explicitly says that the human will is not "resisting and reluctant." The human will freely submits to the divine will. This is not compulsion — it is voluntary agreement. Third, the will is grounded in the nature, not the person. Each nature has its own proper will and its own proper operation. As Wilkinson summarizes, Constantinople III "located a faculty of will in the divine nature and in the human nature of Christ," thereby grounding its dyothelitism "in the person-nature ontology of Chalcedon."²³

B. The Theology Behind Dyothelitism: Why Two Wills Matter

Why does it matter that Christ has two wills? Is this not just obscure theological hair-splitting? Not at all. The stakes are immense. Here are three reasons why dyothelitism is non-negotiable for orthodox Christianity.

First, if Christ does not have a human will, He does not have a complete human nature. The will is an essential faculty of rational human nature. To be human is, among other things, to be able to deliberate, choose, and act. If Christ has no human will, then He is missing a fundamental aspect of what it means to be human — and if He is missing something essential to human nature, then He did not truly become one of us. Gregory of Nazianzus's famous principle applies here: "What is not assumed is not healed."²⁴ If Christ did not assume a human will, then the human will is not healed, not redeemed, not restored. Our wills — the very faculties through which we sin, through which we rebel against God, through which we need redemption — would remain untouched by the Incarnation.

Second, if Christ does not have a human will, His obedience to the Father is not genuinely human obedience. The entire drama of salvation hinges on the fact that where Adam disobeyed, Christ obeyed (Romans 5:19). But if Christ's obedience is purely divine — if it is simply the Son's divine will doing what it always does — then there is no genuine human obedience at all. There is no human agent choosing, in a genuinely human way, to submit to the Father's will. The "new Adam" motif collapses.²⁵

Third, without a human will, the Gethsemane prayer becomes meaningless. And this brings us to the most important biblical text for dyothelitism.

C. Luke 22:42 — The Biblical Heart of Dyothelitism

The single most important biblical text for the doctrine of dyothelitism is Luke 22:42, the Gethsemane prayer:

"Father, if you are willing, remove this cup from me. Nevertheless, not my will, but yours, be done." (Luke 22:42, ESV)²⁶

This verse is, in my judgment, the clearest window into the inner life of the incarnate Son. It is a moment of raw, honest, deeply human anguish. Jesus is facing the cross — the horror of bearing the sins of the world, the prospect of a torturous death, and, most terrible of all, the experience of bearing divine wrath on behalf of humanity. And in this moment, He prays. He asks the Father to take the cup away. But then He submits: "Not my will, but yours, be done."

The Greek is important here. The phrase "not my will" is mē to thelēma mou (μὴ τὸ θέλημά μου) — literally, "not the will of mine." The phrase "but yours" is alla to son (ἀλλὰ τὸ σόν) — "but the [will] of yours." The key word is thelēma (θέλημα), which means "will," "wish," or "desire." Jesus explicitly distinguishes between "my will" and "your will." He uses the first-person possessive mou (μου, "my") for one will and the second-person possessive son (σόν, "yours") for the other. Two different possessives. Two different wills.²⁷

Now, the natural question arises: whose will is the "my" and whose will is the "yours"? The "yours" clearly refers to the Father's will — Jesus is addressing the Father directly. But what about "my will"? Is this Jesus' divine will or His human will?

It cannot be His divine will. The divine will of the Son is identical in content with the divine will of the Father (since the Father and Son share one divine nature and therefore one divine will — the orthodox doctrine of the Trinity affirms this). If "my will" referred to the Son's divine will, then Jesus would be saying "Not what I as God want, but what you as God want" — which makes no sense, because the Father and Son, as God, want the same thing. The divine will does not waver. It does not shrink from the cross. The divine plan of redemption was settled in eternity.²⁸

Therefore, "my will" must be Jesus' human will. And this makes perfect sense. As a genuine human being, Jesus naturally and rightly recoils from suffering and death. He has genuine human emotions — fear, anguish, sorrow (Luke 22:44 tells us His sweat became like drops of blood). His human will genuinely desires to avoid the cup of suffering. This is not sin. This is a proper and healthy human response to the prospect of horrific pain and death. The desire to preserve one's life is a God-given human instinct. Jesus' human will expresses this desire — and then freely submits it to the Father's will.

Maximus the Confessor, the great seventh-century theologian whose work was instrumental in the formulation of dyothelitism at Constantinople III, understood this brilliantly. Maximus recognized that "my will" in Gethsemane referred to Christ's human will — His natural human desire to avoid death. As Andrew Loke explains, Maximus interpreted this prayer as "Not what I as man will, but what you and I as God will."²⁹ The human will has its own natural movement — the desire for self-preservation, the recoiling from pain — but it freely submits to the divine will.

Maximus drew an important distinction that helps us understand this. He distinguished between the natural will (thelēma physikon, θέλημα φυσικόν) and the gnomic will (thelēma gnōmikon, θέλημα γνωμικόν). The natural will is the basic volitional capacity that belongs to a nature — the power to desire, choose, and act. Every human being has a natural will simply by virtue of being human. The gnomic will, by contrast, involves deliberation, uncertainty, and the personal mode in which the natural will is exercised — it is the will as shaped by the particular person's character, habits, and moral disposition. Maximus argued that Christ has a human natural will but does not have a gnomic will in the fallen, uncertain sense, because the gnomic will in fallen humans involves the kind of wavering and moral ambiguity that results from sin. Christ's human will operates perfectly, always freely choosing what is good.³⁰

The point is this: Luke 22:42 is not just a beautiful prayer. It is a window into the metaphysical structure of the incarnate Christ. It presupposes two distinct wills — human and divine — operating within one Person. The human will has its own genuine desires. The divine will has its eternal purposes. And the human will freely submits. This is not a conflict — it is a harmony. As Constantinople III declared, the wills are "not contrary the one to the other."

D. Maximus the Confessor and the Triumph of Dyothelitism

No discussion of dyothelitism is complete without acknowledging the extraordinary contribution of Maximus the Confessor (580–662 AD). Maximus is, in many ways, the theologian most responsible for the triumph of dyothelitism. He suffered terribly for this conviction — his tongue was cut out and his right hand was cut off by imperial authorities — and he died in exile. But his theology ultimately prevailed at Constantinople III, vindicating his courageous stand.

Maximus's key insight was that the will belongs to the nature, not the person. This is a critical distinction. The monothelites argued that if Christ had two wills, He would have two "willers" — two agents, two persons — which would be Nestorianism (the heresy of dividing Christ into two persons). Maximus responded by showing that this argument confuses will with person. The will is a faculty of the nature. Just as every human nature comes equipped with a human intellect and human emotions, so every human nature comes equipped with a human will. The will is part of the standard equipment of the nature, so to speak. The person is the one who uses the will — the agent who exercises the volitional capacity. But the capacity itself belongs to the nature.³¹

This distinction is elegant and powerful. It means that Christ can have two wills without being two persons. The one Person — the Son — exercises both wills. He wills divinely through His divine nature and humanly through His human nature. There is one "willer" (the Person of the Son) and two "willings" (divine and human). As David Bathrellos explains in his study of Maximus: "There are two self-determining faculties (the human and divine wills), but only one self (the 'willer')."³²

Maximus also provided a powerful argument from Scripture beyond the Gethsemane prayer. He pointed to Mark 7:24, which says that Jesus "entered a house and did not want anyone to know it, yet he could not be hidden." Maximus reasoned: if Christ willed to remain hidden by His divine will (which is omnipotent), He would have remained hidden. The fact that He could not remain hidden shows that it was by His human will — distinct from and different (though not opposed) to His divine will — that He desired to go unnoticed. The human will willed something that the divine will did not bring about, proving that the two wills are genuinely distinct.³³

E. Dyothelitism and the Human Soul

Here is where dyothelitism connects directly to the central argument of this book. A will — a genuine faculty of willing — requires a rational soul as its seat. The will is not a property of matter. It is not a physical force. It is a rational, moral, volitional capacity — the ability to deliberate, to weigh options, to choose, and to act on the basis of reasons. On the dualist view, this capacity belongs to the soul. The soul is the seat of the intellect and the will. The human will of Christ is a faculty of His human soul.³⁴

On physicalism, the "human will" would have to be reduced to a brain function — a pattern of neural activity in Jesus' brain. But can a brain function meaningfully "submit" to a divine will? Think about what submission involves. It requires at least three things: (1) a genuine alternative — the human will could have refused to submit; it was not forced; (2) a rational agent who deliberates — who weighs the horror of the cross against the Father's purpose and freely chooses to obey; and (3) a moral act of self-surrender — a genuine giving over of one's own desires to a higher purpose. On physicalism, each of these is problematic.

If the human will is nothing more than a neural event — a pattern of electrochemical activity in the physical brain — then the "submission" of the human will to the divine will is just the occurrence of one physical state rather than another. It is not a genuine choice made by a rational agent; it is the inevitable outcome of prior physical causes. The neural activity in Jesus' brain was determined by the laws of physics operating on the physical states of His neurons. There was no agent who stood above the physical process, weighed the options, and chose. There was just physics happening. The "submission" becomes a physical inevitability, not a moral achievement.³⁵

But the councils clearly understood the human will as something far more than a brain state. They understood it as a genuine faculty — a rational, moral capacity — belonging to the human nature. Maximus, the great champion of dyothelitism, understood the will as "not just the irrational, vital, instinctive and desirous aspect (e.g. the desire for self-preservation, the desire to eat, to drink, to avoid death etc.), but also the rational, self-determining aspect of the human soul."³⁶ The will is a faculty of the soul. It belongs to the immaterial, rational dimension of human nature. Without a soul, there is no human will in the sense the councils intended — and dyothelitism collapses.

F. Loke's Kryptic Model and Dyothelitism

How does dyothelitism fit with the Kryptic Model that I have adopted as my preferred framework for understanding the Incarnation? The answer is: beautifully.

On Andrew Loke's Divine Preconscious Model, Christ has one stream of consciousness — a genuinely human conscious experience. But He has two wills: a divine will and a human will. The human will operates at the conscious level. The divine will is always present and operates in harmony with the human will. The key is that the two wills are not two competing conscious experiences — they are two volitional faculties belonging to two different natures, both exercised by one Person.³⁷

In Gethsemane, the human will — operating at the conscious level — genuinely desires to avoid suffering. This is a real, felt, experienced human desire. The divine will — present at the preconscious level — ordains the cross for the salvation of humanity. The human will, in a genuine moral act of submission, freely conforms itself to the divine will. The "struggle" is real — not in the sense that the divine and human wills are fighting each other, but in the sense that Jesus' human consciousness genuinely experiences the anguish of choosing the Father's will over His natural human desire to avoid pain. This is what Hebrews 5:8 means when it says that "although he was a son, he learned obedience through what he suffered." The obedience is genuinely learned through genuine human experience.³⁸

This is only possible if Christ has a genuine human soul with a genuine human will. The Kryptic Model requires it. On physicalism, the "human will" reduces to brain activity, and the careful architecture of Loke's model — conscious human experience, preconscious divine attributes, genuine human willing — all collapses. As we will explore in more detail in Chapter 17, the Kryptic Model simply cannot function on physicalist assumptions.

III. The Communicatio Idiomatum: The Communication of Attributes

A. What Is the Communicatio Idiomatum?

The communicatio idiomatum — Latin for "communication (or sharing) of idioms (or attributes)" — is one of the most fascinating and practically important doctrines in all of Christology. It addresses a question that every Christian faces, even if they have never heard the technical term: how can we say that the same Person, Jesus Christ, is both omniscient and limited in knowledge, both immortal and mortal, both omnipresent and located in a specific place? These seem like flat contradictions. If Jesus is God, how can He die? If Jesus is man, how can He be eternal?

The communicatio idiomatum answers: because both natures belong to the same Person, the properties of each nature can be predicated of the Person. The properties belong to the natures, but they are said of the Person. So we can truthfully say "The Son of God died" — even though the divine nature cannot die — because the Son of God possesses a human nature, and it is according to His human nature that He died. Similarly, we can truthfully say "The man Jesus Christ created the universe" — even though no human nature can create a universe — because the man Jesus Christ is also the eternal Son of God, and it is according to His divine nature that all things were made.³⁹

The basic rule of the communicatio idiomatum is this: properties of either nature can be predicated of the Person, but properties of one nature cannot be predicated of the other nature. You can go from the natures to the Person, but you cannot go from one nature to the other nature. You can say "Christ is omnipotent" (true according to the divine nature) and "Christ grew in wisdom" (true according to the human nature). But you cannot say "Christ's human nature is omnipotent" — because omnipotence belongs to the divine nature, not the human nature. And you cannot say "The divine nature died" — because death is a property of the human nature, not the divine nature. As Joseph Pohle summarized: "The communication of predicates is valid when done from the natures to the person, but not when done from the person to the natures."⁴⁰

B. Examples of the Communicatio Idiomatum

Let me provide several concrete examples to make this clearer, because these illustrate exactly how the doctrine works in practice.

Example 1: The Son is omniscient and grew in wisdom. How can the same Person be all-knowing and also increase in knowledge? Because the Son possesses two natures. According to His divine nature (qua divine), the Son knows all things — He is omniscient. According to His human nature (qua human), the Son's human mind genuinely grew and developed, as Luke 2:52 tells us: "And Jesus increased in wisdom and in stature and in favor with God and man." There is no contradiction, because the two properties belong to different natures of the same Person.⁴¹

Example 2: The Son is immortal and died. According to His divine nature, the Son cannot die — He is the eternal, immortal God. According to His human nature, the Son truly suffered and died on the cross. As Pope Leo declared in his famous Tome: "Each nature retains its own properties without loss; and just as the form of God does not take away the form of a servant, so the form of a servant does not detract from the form of God."⁴² The death was real — not play-acting, not an illusion. But it was a death according to the human nature, not the destruction of the divine nature.

Example 3: The Son is omnipresent and was located in Palestine. According to His divine nature, the Son is present everywhere — He fills all things. According to His human nature, the Son was born in Bethlehem, grew up in Nazareth, walked the roads of Galilee, and was crucified outside Jerusalem. He was in one place at one time, just as every human being is. On Loke's Kryptic Model, the divine attribute of omnipresence was present at the preconscious level — the Son never ceased to be omnipresent qua divine — but His human conscious experience was spatially located.

Example 4: A member of the Trinity suffered. This is one of the most dramatic applications of the communicatio idiomatum. The councils demanded that Christians affirm that "one of the Holy Trinity suffered in the flesh." Constantinople II's tenth anathema insists on this.⁴³ How can a Person of the Trinity suffer? Because the Person of the Son possesses a human nature, and it is according to that human nature that He suffered. The suffering is not predicated of the divine nature (God does not suffer qua divine nature), but it is predicated of the Person — and the Person is a member of the Trinity.

C. Pawl's Response to the Problem of Apparently Contradictory Predicates

The communicatio idiomatum creates what appears to be a major logical problem. If we predicate both divine and human properties of the same Person, we seem to end up with contradictions: "Christ is omniscient" and "Christ is not omniscient." "Christ is immortal" and "Christ is mortal." "Christ is impassible" and "Christ is passible." These look like the form p and not-p — straightforward logical contradictions.

Pawl takes this problem very seriously. In fact, he devotes several chapters of In Defense of Conciliar Christology to addressing it. He calls this "the Fundamental Problem" of Christology: how can seemingly incompatible predicates be truly predicated of the same subject?⁴⁴

The most common response in the history of Christian theology has been the "qua" strategy — adding a qualifying clause to resolve the apparent contradiction. "Christ is omniscient qua divine" and "Christ is limited in knowledge qua human." The qua clause tells us which nature is the basis for the predication. Pawl examines this strategy with extraordinary care, identifying four different ways the "qua" clause might be understood: (1) as modifying the whole assertion; (2) as modifying the subject (so the subject is really "Christ-qua-divine"); (3) as modifying the predicate (so the predicate is really "omniscient-qua-divine"); or (4) as modifying the copula (so the "is" becomes "is-qua-divine").⁴⁵

Pawl finds problems with several of these approaches, though some are more promising than others. But his most innovative contribution is his own solution in a later chapter, where he argues that the apparently incompatible predicates — like "passible" and "impassible" — are not, in fact, incompatible when properly understood. On Pawl's view, we need to understand these predicates not as one-place properties ("Christ is passible, period") but as properties that are true in virtue of Christ's natures. "Christ is passible" means "Christ has a nature that is able to be causally affected." "Christ is impassible" means "Christ has a nature that is unable to be causally affected." Both can be true simultaneously, because Christ has two natures — one that is passible (the human nature) and one that is impassible (the divine nature).⁴⁶

This is a brilliant move. It resolves the apparent contradiction without requiring any exotic modifications to our logic. The predicates are not really contradictory — they only appeared to be because we were reading them as one-place properties when they actually involve implicit reference to the natures through which they are true.

D. The Historical Development of the Communicatio Idiomatum

The doctrine of the communicatio idiomatum has a long and rich history in Christian theology. It did not spring fully formed from the conciliar definitions. Rather, it developed gradually as the church wrestled with the implications of the hypostatic union.

We see early forms of the communicatio idiomatum in the church fathers. Ignatius of Antioch, writing around 110 AD, used striking expressions like "the blood of God" and "the suffering of my God."⁴⁷ These are classic examples of the communication of attributes: applying a human property (blood, suffering) to the divine Person. The Alexandrian theologians — particularly Cyril of Alexandria — championed the communicatio idiomatum as essential to a proper understanding of the unity of Christ's person. It was precisely the communicatio idiomatum that was at stake in the controversy over whether Mary should be called Theotokos (Θεοτόκος, "God-bearer"). If the communication of attributes is valid, then we can say that Mary gave birth to God — not because the divine nature was born from a human womb, but because the Person who was born from Mary is God the Son. The Council of Ephesus (431) affirmed the title Theotokos and, in doing so, implicitly affirmed the communicatio idiomatum.

The Reformation era saw significant debate about the scope of the communicatio idiomatum. Lutheran theology, following Martin Luther, developed a strong form of the doctrine that held that certain divine properties were genuinely communicated to the human nature — particularly the property of omnipresence, which Luther used to justify his view that Christ's human body is present everywhere (and therefore present in the bread and wine of the Eucharist). Reformed theology, by contrast, maintained the weaker form: properties are predicated of the Person, not transferred between the natures. The human nature does not become omnipresent; the Person who possesses the human nature is also omnipresent according to His divine nature.⁴⁸

Oliver Crisp helpfully distinguishes the communicatio idiomatum from nature-perichoresis — the doctrine of the mutual interpenetration of the natures. The communicatio idiomatum is about predication — what we can truthfully say about Christ. Nature-perichoresis is about ontology — how the natures are actually related to each other in the union. The two doctrines are related but distinct. Crisp traces perichoresis through Gregory of Nazianzus, Maximus the Confessor, and John of Damascus, noting that the concept underwent significant development over time.⁴⁹

E. The Communicatio Idiomatum and the Three-Part Christology

Loke argues that the communicatio idiomatum is most naturally handled within a concrete nature, three-part Christology — that is, a Christology in which Christ is composed of three "parts" (metaphorically speaking): the divine nature, the human body, and the human soul (distinct from the divine nature). On this three-part view, the properties of each component can be predicated of the Person without confusion, because each component retains its own identity and its own properties.⁵⁰

How does this work in practice? Consider the statement "Christ died." Death, in the context of a body-soul dualist understanding of human nature, is the separation of the soul from the body. When Christ died, His human soul separated from His human body. The body went to the tomb; the soul went to the realm of the dead. But the Person — the Son — remained united to both. So "Christ died" is true because the human nature underwent the separation of soul from body. But the divine nature did not die, and the Person did not cease to exist.

On a two-part Christology (divine nature + human body, with no distinct human soul), this becomes much harder to explain. If there is no human soul, then there is nothing to separate from the body at death. Death, on physicalism, is simply the cessation of biological functioning. And if the human nature is just the body, then when the body stops functioning, the human nature simply ceases to exist. The communicatio idiomatum requires that both natures persist in the union — but on physicalism, one of them does not persist through death. The entire framework of "properties predicated of the Person according to one nature" breaks down if one of the natures no longer exists.⁵¹

F. The Importance of the Qua Distinction for the Incarnation

The qua distinction — "according to" this or that nature — is not just a logical trick. It reflects something deep about the metaphysical structure of the Incarnation. When we say "Christ is omniscient qua divine," we are saying that the property of omniscience belongs to Christ in virtue of His divine nature. When we say "Christ grew in wisdom qua human," we are saying that the property of growing in wisdom belongs to Christ in virtue of His human nature. The qua clause tells us the metaphysical ground of the property — which nature accounts for it.

This is theologically important because it preserves the integrity of both natures. The divine nature is not altered by the Incarnation ("without change"). The human nature is not elevated beyond its natural capacities by the union with the divine nature ("without confusion"). Each nature retains its own proper properties and operations. As the Council of Chalcedon declared, "the property of each nature is preserved and concurs in one person."⁵²

And as Constantinople III further specified, "each nature wills and performs the things that are proper to it in a communication with the other." The natures do not operate in isolation — they operate "in communication." The human nature's properties and the divine nature's properties are both exercised by the one Person, and they harmonize with each other. The human will submits to the divine will. The human knowledge grows while the divine knowledge remains complete. The human body suffers while the divine nature remains impassible. All of this happens within the one Person, not in two separate persons.⁵³

IV. The Physicalist Problem: Why Physicalism Undermines All Three Doctrines

A. The Fundamental Tension

We have now laid out the three great doctrines that form the core of Christological metaphysics: the hypostatic union, dyothelitism, and the communicatio idiomatum. Each of them is essential. Each of them is defined by ecumenical councils. And each of them, as I have been arguing throughout this chapter, presupposes and requires that Christ's human nature includes an immaterial human soul. Let me now bring together the full case for why physicalism — the denial that any human being has an immaterial soul — is incompatible with all three.

The fundamental tension is this: on physicalism, Christ's human nature is purely physical. It is a material body and nothing more. There is no immaterial soul, no immaterial intellect, no immaterial will. Every human property is a physical property — a property of matter, of neurons, of biological processes. This creates a sharp metaphysical problem: how is an immaterial divine nature united to a purely physical human nature?⁵⁴

On dualism, both natures have an immaterial component. The divine nature is immaterial (God is spirit, John 4:24). The human soul is also immaterial. This provides a more natural metaphysical "point of contact" for the union. The soul, as it were, serves as a bridge between the divine and the physical. The divine Person is united to the human soul, and the human soul is united to the human body. There is a metaphysical gradient, if you will, from the fully immaterial (divine nature) through the immaterial-but-created (human soul) to the material (human body).

On physicalism, there is no such gradient. The union is between the purely immaterial (divine nature) and the purely material (body) — with no mediating immaterial component. Now, I want to be fair and say that this does not make the union strictly impossible. God is omnipotent, and if it is logically possible for an immaterial divine nature to be united to a purely material body, then God can bring it about. But it does make the union far more metaphysically puzzling than it needs to be. And more importantly, it is not what the councils intended. The councils defined Christ's human nature as a body-soul composite, not a body alone. Physicalism does not just face a difficulty with the how of the union — it contradicts the what of the human nature as the councils defined it.

B. Physicalism and the Hypostatic Union

We have already touched on this above, but let me state it more precisely. The hypostatic union, as defined at Chalcedon, is the union of the divine and human natures in one Person "without separation." The "without separation" clause means that the union is permanent and unbroken. The natures are never pulled apart.

On dualism, "without separation" is maintained even through Christ's death. When Christ died, His human soul separated from His human body — but the Son remained united to both. The hypostatic union was not broken. The Incarnation continued through Holy Saturday. The Son was still "true God and true man" — even though the human nature was in a state of temporary separation (soul in one place, body in another).

On physicalism, "without separation" cannot be maintained through death. When Christ's body died, there was nothing left of the human nature. The body ceased to be a living human organism. It was now a corpse — dead biological matter. The Son was united to dead matter, which is not a human nature in any meaningful theological sense. For somewhere around thirty-six to forty hours, the Second Person of the Trinity was not incarnate. The hypostatic union was broken. "Without separation" was violated.⁵⁵

This is not a minor problem. This is a catastrophic problem. If the Incarnation was broken at the cross, then the Incarnation is not permanent. It had a gap. The eternal Son was temporarily un-incarnate. This contradicts not only Chalcedon's "without separation" but the entire theological tradition's insistence that the Incarnation is permanent — that the Son remains God and man forever. I will develop this argument fully in Chapters 21 and 22, but the foundation is laid right here, in the doctrine of the hypostatic union itself.

C. Physicalism and Dyothelitism

We have also begun to see the problem with dyothelitism on physicalism, but let me sharpen it further. Constantinople III defined Christ as having two natural wills — divine and human. The human will is a faculty of the human nature. It is the capacity to deliberate, choose, and act. It is what makes the Gethsemane prayer possible: "Not my will, but yours, be done."

On dualism, the human will is a faculty of the human soul. It is an immaterial, rational capacity — the soul's ability to will. This is what the council fathers understood by "will." Maximus the Confessor — whose theology shaped Constantinople III — understood the will as including "the rational, self-determining aspect of the human soul."³⁶ The will is not a brain state. It is a faculty of the soul.

On physicalism, the "human will" would have to be identified with some pattern of neural activity in Jesus' brain. But this raises several profound difficulties.

First, can a brain state genuinely deliberate? Deliberation involves weighing options, considering reasons, evaluating consequences, and choosing on the basis of rational reflection. On physicalism, "deliberation" is just a sequence of physical events in the brain — one neuron firing causes another neuron to fire, which causes another, and so on. There is no agent above the physical process who is doing the deliberating. The "deliberation" is just physics happening. It is not genuinely rational — it is causally determined by prior physical states.

Second, can a brain state genuinely submit? Submission is a moral act. It involves a self who chooses to yield its own desires to the will of another. On physicalism, there is no immaterial self who makes this choice. There are just neural events. The "submission" of Jesus' brain to the Father's will is just the occurrence of one neural pattern rather than another — determined by the physical state of His neurons at that moment. This is not moral submission. This is physical determinism wearing a theological mask.

Third, can a brain state be a genuine will in the sense that the councils intended? The councils understood "will" as a genuine faculty — a real, ontological capacity of the nature. Can a pattern of neural firing constitute such a faculty? On physicalism, the "will" is not a distinct faculty at all — it is an epiphenomenon of physical processes, or (on more austere versions of physicalism) it simply is the physical processes, redescribed in mentalistic language. But the councils were not speaking in metaphors when they affirmed two wills. They were making an ontological claim about the structure of Christ's being. A brain state cannot bear the ontological weight that Constantinople III places on the human will.⁵⁷

D. Physicalism and the Communicatio Idiomatum

The communicatio idiomatum depends on the existence of two distinct natures, each with its own set of properties, united in one Person. The properties of each nature are predicated of the Person. The qua distinction tells us which nature is the metaphysical ground of each property.

On physicalism, every human property is a physical property. The "human properties" that the communicatio idiomatum attributes to Christ — mortality, suffering, growth in wisdom, hunger, fatigue, fear — are all properties of the physical body and brain. There is no additional set of "soul properties" — no immaterial intellect, no immaterial will, no immaterial emotional life. Everything that Christ's human nature contributes to the communicatio idiomatum is physical.

This creates a problem at multiple levels. First, it makes the range of human properties that can be predicated of Christ significantly narrower than the tradition has assumed. If there is no human soul, then Christ does not have the kind of rich inner life — intellectual, volitional, emotional — that the tradition has always attributed to Him. His "wisdom" is neural complexity. His "will" is a brain process. His "love" is a neurochemical event. The properties being predicated of the Person are mere physical properties, not the deep, rational, moral, spiritual properties that the fathers had in mind.

Second, it creates a problem for the continuity of the communicatio idiomatum through death. If the human nature ceases to exist at death (because there is no soul to survive), then there are no human properties to predicate of the Person during the triduum mortis. The entire human side of the communicatio idiomatum disappears for three days. The Person is no longer both omniscient and limited in knowledge — He is just omniscient. He is no longer both immortal and mortal — He is just immortal. He is no longer both omnipresent and located — He is just omnipresent. The dual predication that makes the communicatio idiomatum so striking and so important is temporarily abolished. This is another way of saying what we have already said: the Incarnation is interrupted at the cross, and the full Christological framework collapses during the triduum.⁵⁸

Third, if we accept Loke's concrete nature, three-part Christology — which I do — then the communicatio idiomatum depends on Christ having three distinct components: divine nature, human body, and human soul. On physicalism, there are only two: divine nature and human body. The three-part framework that allows the most satisfying resolution of the communicatio idiomatum puzzles is simply unavailable to the physicalist. The physicalist is forced back onto a two-part Christology (divine nature + body), which Loke, Crisp, and others have shown faces additional difficulties, particularly with dyothelitism and the Apollinarian worry.⁵⁹

E. The Soul as the Metaphysical Bridge

Let me pull this all together with an image. Think of the hypostatic union as a bridge connecting two realms — the divine and the human. On dualism, the bridge has three supporting pillars: the divine nature, the human soul, and the human body. The soul stands in the middle, connecting the immaterial divine nature to the material human body. It provides structural support. It ensures continuity. When the body dies, the soul holds the bridge up — the connection between the divine and the human is maintained.

On physicalism, the middle pillar is removed. There are only two pillars: the divine nature and the human body. The bridge spans directly from the fully immaterial to the fully material with nothing in between. And when the body dies — when one of only two pillars crumbles — the bridge collapses entirely. There is nothing left to hold it up.

This metaphor is imperfect, as all metaphors of the Incarnation are. But it captures something important: the soul plays a structurally essential role in the architecture of the Incarnation. It is not a decorative feature. It is load-bearing. Remove it, and the entire structure becomes unstable.

V. Addressing Objections

A. Objection: "The Hypostatic Union Is a Divine Mystery — We Shouldn't Try to Analyze It Metaphysically"

Some readers may feel uncomfortable with the level of metaphysical analysis in this chapter. "Isn't the Incarnation a mystery?" they may ask. "Shouldn't we just accept it by faith rather than trying to break it down into philosophical categories?"

I appreciate this concern, and I agree that the Incarnation is ultimately a mystery. The councils themselves said so — the hypostatic union is "ineffable," beyond full human comprehension.⁶⁰ But there is a crucial difference between mystery and confusion. A mystery is something we affirm as true even though we cannot fully explain it. Confusion is when we affirm something without knowing what we are affirming. The councils engaged in careful metaphysical analysis precisely to avoid confusion — to make clear what the Incarnation is (one Person, two natures) and what it is not (two persons, or one blended nature, or a nature without a soul). The metaphysical framework does not dissolve the mystery — it protects it by drawing clear boundaries around what can and cannot be said.

And as Pawl rightly notes, the conciliar declaration that the union is ineffable actually serves as a constraint on any model: no model should claim to fully explain the union. But models can — and should — show that the union is logically coherent. That is not explaining the mystery away; it is defending the mystery against the charge of contradiction.⁶¹

B. Objection: "Physicalism Is Compatible with Dyothelitism Because the Brain Can Produce Something Like a 'Will'"

A physicalist might respond: "Sure, the brain is physical. But the brain produces incredibly complex mental states — including what we call 'willing.' Why can't the brain's volitional capacities count as a genuine 'human will' in the sense Constantinople III intended?"

This is a fair question, and I want to engage it honestly. The physicalist is right that the brain is astonishingly complex and produces rich cognitive and volitional activity. I do not deny that the brain is involved in willing. On dualism, the soul and the brain work together — the soul exercises the will, and the brain is the physical instrument through which the soul's willing is expressed in the body.

But the issue is not whether the brain is involved in willing. The issue is whether a purely physical process — no matter how complex — can constitute a genuine will in the sense the councils intended. And I believe the answer is no, for several reasons.

First, the councils understood the will as a faculty of the rational soul, not the brain. Maximus was explicit about this. The will belongs to the soul, not to matter. Second, a purely physical process is causally determined by prior physical states. If the "will" is just neural activity, then it is determined by the laws of physics. There is no genuine libertarian freedom — no capacity to choose otherwise. But the councils' understanding of the human will presupposes genuine freedom. The human will freely submits; it is not compelled. Third, as I argued above, the "submission" of a brain state to a divine will is metaphysically puzzling. How does a pattern of neural firing "submit" to anything? Submission is a personal, moral act — not a physical event.⁶²

C. Objection: "The Communicatio Idiomatum Doesn't Require a Soul — It Only Requires Two Natures"

Another objection might be: "The communicatio idiomatum works as long as there are two natures with different properties. Even on physicalism, there are two natures — divine and human (physical). So the communication of attributes can still function."

This is partially correct. The communicatio idiomatum does require two natures, and even on physicalism, there are two natures (divine and human-physical). So in principle, properties can still be predicated of the Person according to one nature or the other. But the problem, as I argued above, is threefold. The range of human properties is impoverished (no soul-properties). The continuity through death is broken (no soul to survive death). And the three-part framework that handles the communicatio idiomatum most effectively is unavailable. The doctrine technically "works" on physicalism in a minimal sense, but it works so poorly that it barely resembles the robust, rich doctrine that the tradition has affirmed.⁶³

D. Objection: "The Councils Were Not Addressing the Dualism-Physicalism Debate"

A final objection deserves attention: "The councils were not engaged in the modern debate about dualism versus physicalism. They assumed dualism because everyone in their culture assumed dualism. But their Christological definitions can be separated from their anthropological assumptions."

I hear this objection, and I understand its appeal. The councils were addressing specific heresies (Apollinarianism, Nestorianism, Eutychianism, monothelitism) — not the modern physicalism-versus-dualism debate. That is historically accurate. But the fact that the councils were not directly addressing our question does not mean their definitions are neutral on it. When Chalcedon explicitly defined Christ's human nature as consisting of "a rational soul and a body," it was not making an incidental cultural assumption. It was making a theological claim — a claim rooted in the anti-Apollinarian tradition that insisted on the completeness of Christ's human nature. The council deliberately included "rational soul" in its definition because it had just fought a prolonged battle against Apollinarius, who denied it. The "rational soul" language is anti-heretical armor, not cultural decoration.⁶⁴

Furthermore, as Wilkinson has convincingly argued, we should move from Christology to anthropology, not the other way around. If the councils define Christ's human nature as body + rational soul, then a proper theological anthropology should follow suit. Human nature, as revealed in Christ, includes a body and a rational soul. To adopt physicalism is to adopt an anthropology that contradicts the Christological definition — which is exactly backwards. The man par excellence should govern our definition of human nature par ordinaire, not the other way around.⁶⁵

VI. The Interconnection of the Three Doctrines

Before we conclude, I want to step back and observe how beautifully these three doctrines — the hypostatic union, dyothelitism, and the communicatio idiomatum — fit together. They are not three isolated ideas. They are three aspects of a single, integrated Christological vision.

The hypostatic union tells us the structure: one Person, two natures. Dyothelitism tells us the function: each nature has its own proper will and operation. The communicatio idiomatum tells us the predication: how the properties of each nature can be truthfully attributed to the one Person. Together, they give us a complete picture of who Christ is and how His two natures operate within the unity of His Person.

Wilkinson captures this interconnection with particular clarity. He observes that by applying the person-nature distinction, Constantinople III declared that Christ is God the Son incarnate according to a person-nature constitution such that He acts according to a person-nature function, both as God and as man.⁶⁶ Distinction, constitution, and function — three aspects of a single reality. The Person is distinguished from the natures. The natures constitute the Person's being. And the Person functions through the natures.

And here is the critical point: each of these three aspects requires the human soul. The hypostatic union requires a soul to maintain continuity through death. Dyothelitism requires a soul as the seat of the human will. The communicatio idiomatum requires a soul to provide the full range of human properties and to sustain the three-part framework. Remove the soul, and all three doctrines are undermined — not destroyed entirely, perhaps, but so weakened and impoverished that they can barely function.

This is why the physicalism-versus-dualism debate is not an abstract philosophical side issue. It strikes at the very heart of who Jesus Christ is. The architecture of the Incarnation — the hypostatic union, dyothelitism, and the communicatio idiomatum — is built on the foundation of the human soul. Pull out that foundation, and the entire structure becomes unstable.

VII. Conclusion: The Soul-Shaped Architecture of Orthodox Christology

We have covered a great deal of ground in this chapter, and I want to pull together the main threads.

The hypostatic union — the union of the divine and human natures in the one Person of the Son — is the central mystery of the Christian faith. It is defined by the four Chalcedonian adverbs: without confusion, without change, without division, without separation. On substance dualism, the hypostatic union is metaphysically coherent: the Son is united to a body-soul composite, and the soul ensures continuity even through death. On physicalism, "without separation" is violated at the cross, because the human nature ceases to exist when the body dies.

Dyothelitism — the doctrine of two wills, defined at Constantinople III — teaches that Christ has a divine will and a human will, operating in harmony within one Person. The human will is a faculty of the human soul — a rational, moral, volitional capacity. On physicalism, the "human will" reduces to neural activity, which cannot bear the ontological weight of genuine deliberation, moral submission, and free choice. Luke 22:42 — "Not my will, but yours, be done" — presupposes two genuine wills, one human and one divine, and the human will's free submission is the heart of Christ's saving obedience.

The communicatio idiomatum — the communication of attributes — teaches that the properties of both natures can be predicated of the one Person. On dualism, this works beautifully within a three-part framework (divine nature, human soul, human body) that provides the full range of human properties and maintains continuity through death. On physicalism, the range of human properties is impoverished, the continuity through death is broken, and the three-part framework is unavailable.

All three doctrines point in the same direction: Christ's human nature must include an immaterial human soul. The soul is not an optional philosophical add-on. It is a constitutive element of the Christological framework that the ecumenical councils defined. Physicalism, by denying the soul, undercuts the very doctrines it claims to affirm. It cannot sustain the hypostatic union through death. It cannot sustain dyothelitism as the councils understood it. And it cannot sustain the communicatio idiomatum in its full, rich, tradition-affirmed form.

In the next chapter, we will turn to a specific model of the Incarnation that has tried to avoid these problems by going in a very different direction: kenotic Christology, which holds that the Son emptied Himself of divine attributes in order to become incarnate. We will see why this approach, despite its intentions, creates problems at least as serious as the ones it tries to solve — and why the kryptic model (explored in Chapter 17) provides a far better alternative.⁶⁷

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