Hypostatic Union: Explaining the Two Natures of Jesus

Disclaimer: The views and opinions expressed in this article belong to the author and do not necessarily match my own. - Dr. Bart D. Ehrman

What is the hypostatic union? This is the question I often pose to my students, usually right after they tell me they’re practicing Catholics who attend Sunday Mass each week. Strangely enough, almost none of them has ever heard of the term. Not “hypostatic,” not “union,” not even a vague sense of what the phrase might refer to.

That reality has always fascinated me. How can this be? Here are people who identify strongly with their faith tradition, participate regularly in its most central ritual, and yet remain unfamiliar with one of the most foundational doctrines of Christianity. 

Wouldn’t you want to know what the religion you so deeply value actually teaches at its core? Apparently, not always.

And yet, the doctrine of the hypostatic union lies at the very heart of mainstream Christian theology. It refers to the claim that Jesus Christ is fully God and fully man, two complete natures united in one person.

This belief gradually emerged as the culmination of centuries of theological reflection, debate, and often bitter controversy. The process involved a wide array of competing views about Jesus’ identity, many of which were eventually declared heretical, though they were once held by some of the most intellectually sophisticated Christians of their day.

This article traces that historical journey. We’ll begin by exploring how early Christian communities (rooted in a deeply monotheistic Jewish tradition) grappled with the divine claims made about Jesus. 

We’ll then survey the major Christological positions that emerged in the 2nd through 4th centuries: Adoptionism, Apollinarianism, Arianism, Monophysitism, and Nestorianism.

Finally, we’ll arrive at Chalcedon and examine how the formulation of the hypostatic union came to define what would be, for most Christian traditions, the definitive answer to the question: Who was Jesus?

Importantly, this article isn’t an exercise in theological advocacy. We aren’t endorsing or rejecting any particular belief or disbelief about Jesus’ divinity. Rather, our goal is to approach these topics historically.

How did early Christians articulate their beliefs? What kinds of debates shaped those articulations? These are the questions that will guide us in the pages that follow. 

However, before our journey into the wild diversity of early Christian views about Jesus’ identity begins, we thought, “Why not make life easier for our readers!?”

So, because we’re cool like that (and because we believe you deserve nothing less than the best), we’ve crafted a neat little table that lays out the key Christological schools in one quick glance. Consider this your theological cheat sheet. No heavy lifting required!

Where Did It All Begin? Centuries Before the Hypostatic Union

Today, most critical scholars agree on a broad understanding of who Jesus really was. Needless to say, there are still many debates and polemics regarding various elements of his self-understanding, but there is a consensus about some key aspects.

In his book How Jesus Became God, Bart D. Ehrman asserts:

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These are the words of a contemporary scholar who has spent decades studying and analyzing the earliest sources about Jesus to formulate historical reconstructions and plausible conclusions. 

To put it more bluntly, the Jesus described here isn’t a figure of full-blown Trinitarian theology, nor one consciously promoting what would later be called the hypostatic union.

Instead, he is a deeply Jewish apocalyptic preacher (firmly rooted in the worldview of 1st-century Palestine) who expected divine intervention to inaugurate God’s kingdom and envisioned himself as a central figure within it.

The origins of Christological controversy lie precisely in the tension between this historical figure and the theological claims that began to swirl around him in the decades and centuries after his death. Much of that tension can already be detected in the New Testament itself.

We often forget that the New Testament isn’t a unified book but a collection of writings composed by different authors at different times, each offering distinct perspectives. It should not surprise us, then, that the language used to describe Jesus contains paradoxical (and sometimes competing) affirmations.

On the one hand, the humanity of Jesus is portrayed with striking clarity. The Synoptic Gospels place Jesus firmly within the world of 1st-century Judaism. Apart from his miracles, Jesus appears fully human: He is born, grows hungry, experiences sorrow, associates with others, and dies a very human death.

At the same time, the New Testament also contains high Christological affirmations. The Gospel of John opens with the striking claim that “the Word became flesh” (John 1:14), identifying Jesus not just as a messenger from God but as the divine Logos incarnate. John 13:3 speaks of Jesus coming from God and returning to God.

The Book of Hebrews reinforces this divine portrait by declaring Jesus to be the agent through whom the world was created (Hebrews 1:2), who “comes into the world” from a preexistent state (Hebrews 1:6; 10:5).

Even Matthew, which is generally considered to reflect a more Jewish perspective, depicts Jesus' birth as a supernatural event, a fulfillment of divine prophecy involving a virgin conception. On top of all that came the early belief that God raised and exalted Jesus! 

These theological layers coexist with the more human portrayals and are evidence of how early Christian communities were already wrestling with Jesus' identity in complex ways.

In his book The Writings of the New Testament, Luke T. Johnson explains the complexity that dominated early Christian world:

This paradox (Jesus as both fully human and somehow divine) sits at the root of the Christological debates that would dominate the church’s first several centuries. The earliest followers of Jesus didn’t begin with a settled doctrine; they began with experiences, memories, imaginations, and convictions that eventually required intellectual and theological clarification.

The doctrine of the hypostatic union would ultimately emerge as an attempt to resolve this tension, to provide a coherent framework in which both Jesus’ divinity and humanity could be affirmed without contradiction. 

But that resolution was a long time coming. And needless to say, it never managed to satisfy every Christian community!

But the main point is that the story of the hypostatic union, then, begins not with agreement, but with deep and enduring diversity! A diversity that only amplified in the centuries following Jesus’ death.

Christological Schools and Their Controversies (2nd-5th Centuries)

It was the great Catholic scholar Raymond E. Brown who once observed what he called the “backwards trajectory” of Christology in the canonical Gospels. In the latest Gospel to be written (John) Jesus’ divine status is placed prior to his earthly existence: He is the preexistent Word who was “with God” and who was God. 

By contrast, in the earliest Gospel (Mark) Jesus’ divinity is traced to a particular moment in time: His baptism in the Jordan River, when the heavens open and a voice declares, “You are my beloved Son.” 

Going even further back, Brown noted certain pre-Pauline traditions preserved in the speeches of Acts in which Jesus’ exaltation to divine status is said to occur only at the resurrection.

In short, early Christian texts offered multiple, competing models of when (and even whether) Jesus became divine. As Bart Ehrman, in How Jesus Became God, notes:

The branch of thought that emphasized Jesus’ elevation to divine status (whether at his baptism or resurrection) came to be known as Adoptionism.

The term is a modern scholarly label derived from the idea that Jesus, though born a mere human, was “adopted” as God’s Son by divine decree. This model found early proponents such as Theodotus of Byzantium in the late 2nd century, who taught that Jesus was empowered by the Spirit at his baptism and was rewarded for his virtue with divine status.

If Adoptionism placed its emphasis on Jesus’ humanity, Arianism took a very different tack. Named after Arius, a presbyter of Alexandria active in the early 4th century, this view held that Jesus wasn’t co-eternal with the Father. He was divine, yes, but a secondary divinity, created by God before the world began. There was a time, Arius famously insisted, when “the Son was not.” 

This formulation was too much for most bishops to accept, especially those seeking to maintain Jesus' full and unqualified divinity. The dispute became so heated that the Roman Emperor Constantine himself stepped in, convening the Council of Nicaea in 325 C.E. in an attempt to restore unity.

Although the Nicene Creed famously condemned Arius’ position, the controversy did not end there, despite Constantine’s determined efforts, which culminated in Arius’ expulsion. It appears that even Constantine himself underestimated the depth of the tensions and divisions.

Klaus M. Girardet, in his book Der Kaiser und sein Gott: Das Christentum im Denken und in der Religionspolitik Konstantins des Großen (The Emperor and His God: Christianity in the Thought and Religious Policy of Constantine the Great), explains:

Into this already fractious environment stepped Apollinaris of Laodicea (c. 310-c. 390), who doubled down on the full divinity of Christ, perhaps a bit too much.

Aloys Grillmeier, in his study Christ in Christian Tradition: From the Apostolic Age to Chalcedon, explains Apollinarius’ starting position:

In other words, Apollinaris insisted that the divine Logos had taken the place of a rational human soul in Jesus. That is, Jesus had a human body but not a human mind or will; those functions were fulfilled by the eternal Word.

This formulation became known as logos-sarx Christology (Word-flesh), and it found a particularly receptive home in Alexandria. But critics pointed out a glaring problem: If Jesus lacked a human mind, how could he be said to have fully assumed the human condition?

In reaction to Apollinaris and the Alexandrian camp more broadly, theologians from Antioch emphasized Christ’s full humanity. This position, known as logos-anthropos Christology (Word-man), maintained that the divine Word was united not to just a human body, but to a complete human person. 

Pushing this idea to its limits was Nestorius, a monk from Antioch who became archbishop of Constantinople in 428. 

Nestorius was especially concerned to protect the distinction between Jesus’ divine and human natures.

Christiane Fraisse-Coué provides an excellent summary of Nestorius’ views:

Needless to say, this didn’t go over well. Nestorius' fiercest opponent was Cyril of Alexandria, a theologian as brilliant as he was combative. Cyril saw Nestorius’ position as a dangerous division of Jesus into two persons and sprang into action with remarkable speed and intensity.

By 429, he had already penned refutations and lobbied Pope Celestine I in Rome, who agreed to condemn Nestorius at a synod in 430. The following year, Emperor Theodosius II convened the Council of Ephesus to resolve the issue. The council, effectively dominated by Cyril and his allies, condemned Nestorianism and affirmed Mary’s title as Theotokos.

Nestorius was deposed and exiled, and while his followers would eventually form a separate church (most notably flourishing in Persia) his teachings were forbidden within the empire.

The council may have tried to settle the matter, but new controversies soon followed. In 447, yet another theologian stirred the pot, this time from the monastic world of Constantinople. Eutyches (c. 378-454), an archimandrite in the city, began teaching that Jesus had only one nature (monē physis) after the incarnation.

In his effort to preserve the unity of Jesus’ person against what he saw as Nestorius’ divisive dualism, Eutyches went too far in the opposite direction. His view (later termed Monophysitism) essentially erased Jesus’ human nature. The divine had so absorbed the human, he claimed, that only one nature remained. 

This position, unsurprisingly, alarmed those who had just fought so hard to preserve Christ’s full humanity.

But Eutyches was undeterred. Faced with mounting opposition, he appealed directly to the imperial court. After all, the emperor Theodosius II had thus far backed the Monophysite position, surely he would continue to support a devout monk defending the singular nature of Christ, right? 

Well… not quite. Before any firm decision could be cemented, Theodosius II unexpectedly died. And with his death, the political tides shifted rapidly. Eutyches would soon discover that emperors may favor you one day and vanish the next, along with your theological fortunes.

What came next would take place at a council we’ve yet to discuss: Chalcedon. But that, as they say, is another chapter in the saga…

Council of Chalcedone and the Rise of Hypostatic Union

Before any imperial judgment was rendered, another (and arguably more decisive) intervention occurred. That intervention came from none other than the bishop of Rome, Pope Leo I, whose theological weight and political influence would soon shift the entire course of the Christological debates.

In 449 CE, Leo penned a dogmatic letter, famously known as the ”Tome of Leo,” addressed to the Patriarch of Constantinople. In it, he sought to clarify the “orthodox” position: That there were two natures of Jesus, one human and one divine, united in one person (persona).

The divine and the human, Leo insisted, are neither confused nor divided! 

After Theodosius’ death in 450, his sister Pulcheria and her husband, the new emperor Marcian, reversed imperial support and aligned themselves with Leo and the Western bishops.

In response to the mounting tensions and theological divisions, they called a new ecumenical council to be held in Chalcedon, near Constantinople, in the autumn of 451. It was at Chalcedon that the long-brewing debates over Jesus’ nature(s) reached a defining moment.

Drawing heavily on Leo’s Tome, the council sought a middle path between Nestorius and Eutyches (between dividing Jesus into two persons and reducing him to a single divine nature). When Leo’s letter was read aloud at the council, an enthusiastic acclamation allegedly broke out among the bishops: “Peter has spoken through Leo! This is what we believe!”

The council’s decree was as theologically dense as it was rhetorically elegant. It declared that Jesus Christ is one single Christ, Son, Lord, Monogenic, without confusion, without change, without division, without separation, the difference in natures being in no way suppressed by the union, but rather the properties of each being safeguarded and reunited in a single person and a single hypostasis.

That final word (hypostasis) became the defining term of the council’s Christology. This was the hypostatic union: The teaching that in the one person, two natures of Jesus (divine and human) exist in perfect, indivisible unity.

This doctrine became the cornerstone of orthodox Christology in both the Western Church and the Eastern (Byzantine) imperial tradition. But that didn’t mean everyone accepted it! 

On the contrary, the decisions of Chalcedon provoked fierce backlash in large parts of the Christian East. In Egypt, Syria, and Palestine, many believers continued to hold to Monophysite convictions, rejecting Chalcedon as a betrayal of true faith. The council, in their eyes, compromised Jesus' unity. 

Even as imperial edicts attempted to enforce Chalcedonian orthodoxy, the opposition proved remarkably resilient. For more than two centuries after Chalcedon, emperors and bishops fought (sometimes with theology, sometimes with soldiers) to impose or suppress rival views.

But despite imperial authority and ecclesiastical muscle, the Monophysite churches survived. They endured marginalization, persecution, and theological condemnation. And then, in the 7th century, something extraordinary happened.

A new religious and political force swept through Egypt, Syria, Palestine, and beyond, conquering vast territories once ruled by Byzantium. These were precisely the lands where anti-Chalcedonian Christians were quite popular.

Can you guess who came? Let’s just say… it wasn’t a council that silenced the Monophysites. It was something (or someone) else entirely!

Conclusion

In light of everything we’ve explored, it’s not all that surprising that so few people today (my students included!) have heard of the hypostatic union. The doctrine, after all, is the product of centuries of theological refinement, philosophical speculation, and imperial politics.

What began as a movement centered on the teachings and crucifixion of a 1st-century Jewish preacher eventually evolved into a highly sophisticated set of claims about divine and human natures united in one person; claims formalized (but never fully agreed upon!) only after generations of controversy and debate.

And yet, the very fact that this doctrine endured, debated and defined across empires, tells us something about the power of ideas in shaping religious identity. The hypostatic union isn’t just a piece of abstract theology. Rather, it’s a window into how early Christians wrestled with the mystery of Jesus’ identity and what was at stake in their answers.

Whether one accepts the doctrine or not, its story reveals a profound and very human struggle that shaped the most influential religion in the history of Western civilization.

FAQ: Questions About Jesus’ Identity

It’s not over yet! In discussions about Jesus’ divinity and humanity, certain questions come up again and again, sometimes from students, sometimes from curious readers.

Below, we briefly explore a few of these perennial favorites. It’s important to note that our goal here is to present how mainstream Christian theology has traditionally responded, without endorsing or rejecting any particular belief.