How can one Jesus be both God and man without being two people or a mixture of the two? The early Church answered with a small set of carefully chosen words.
In brief
The hypostatic union is the name for the union of divinity and humanity in Jesus Christ. It says that there is one person in Christ, the eternal Son of God, and that this one person exists in two complete natures, divine and human, which are united without being mixed and distinguished without being separated. The word hypostatic comes from the Greek hypostasis, which in this setting means the personal subject: the union happens in the person of the Son. This article explains the terms, shows the errors they were coined to exclude, and draws out two consequences that are easy to miss: the communication of properties, which lets Christians say that God was born and died, and the teaching that Christ has a human will as well as a divine one. For why the union matters for salvation, see the cornerstone article Why Did God Become Man?; for the history of the council that defined it, see What Did the Council of Chalcedon Actually Define?
On this page
- The problem the words solve
- Person and nature
- Four ways to get it wrong
- Chalcedon's four words
- The communication of properties
- Two wills
- Is it coherent?
- What we can say confidently
- What remains disputed
- Notes
The problem the words solve
The New Testament speaks about Jesus in two ways at once. It calls him God: the Word who “was God” and “became flesh”,1 the one Thomas addresses as “My Lord and my God!”,2 the one in whom “all the fullness of the Deity dwells bodily.”3 It also describes an ordinary human life. Jesus “increased in wisdom and stature, and in favor with God and men.”4 He was hungry and tired. At the tomb of a friend, “Jesus wept.”5 Of the last day he says that “no one knows, not even the angels in heaven, nor the Son, but only the Father.”6
Both sets of statements are made about the same subject, and Paul can combine them in one sentence: the rulers of this age “wouldn’t have crucified the Lord of glory.”7 The early Church's task was to find a way of speaking that kept both sets of statements true without dissolving either. Very early on, the answer was stated in paradox. Ignatius of Antioch, writing around the beginning of the second century, calls Christ the “one Physician who is possessed both of flesh and spirit; both made and not made; God existing in flesh; true life in death; both of Mary and of God”.8 The later technical vocabulary is an attempt to say precisely what Ignatius said in poetry.
Person and nature
The key is a distinction between who someone is and what someone is. A nature (Greek physis, closely related to ousia, essence or substance) is what a thing is: the set of properties that make something human, or divine. A person or hypostasis is who someone is: the concrete subject who has a nature and to whom actions and experiences belong. When we say Peter walks and Peter thinks, Peter is the one subject, and walking and thinking belong to the human nature he has.
Applied to Christ, the distinction gives the Church's answer. There is one who in Christ: the eternal Son, the second person of the Trinity. There are two whats: the divine nature he has always had and shares with the Father and the Spirit, and the complete human nature, body and rational soul, that he took from his mother. The union is hypostatic because it happens in the hypostasis, the person. Cyril of Alexandria used the term in his anathemas against Nestorius in the fifth century:
“If anyone shall not confess that the Word of God the Father is united hypostatically to flesh, and that with that flesh of his own, he is one only Christ both God and man at the same time: let him be anathema.”
Two misunderstandings should be set aside at once. The human nature of Christ is not a separate human being whom the Son befriended or inhabited; it never existed on its own before or apart from the union. And the Son did not bring a human person into being alongside himself; the Son himself is the one who is born, grows, suffers and dies, in the nature he made his own.
Four ways to get it wrong
The vocabulary was hammered out against positions that each kept one part of the biblical witness by sacrificing another. They are easiest to remember as four boundary lines.
Denying that he is fully God. Arius in the fourth century taught that the Son was the first and highest creature. The Council of Nicaea answered that the Son is of one substance with the Father, and the creed of 381 confesses him as “very God of very God, begotten not made”.10 The site's article on Athanasius against the Arians tells that story.
Denying that he is fully human. Apollinarius of Laodicea taught that the divine Word took the place of a human mind in Christ. Gregory of Nazianzus answered that such a Christ could not save the human mind: “If anyone has put his trust in Him as a Man without a human mind, he is really bereft of mind, and quite unworthy of salvation. For that which He has not assumed He has not healed”.11
Dividing him into two subjects. Nestorius, bishop of Constantinople, objected to calling Mary Theotokos, the one who gave birth to God, and his opponents took him to mean that the man Jesus and the divine Word were two subjects joined by a moral partnership. Cyril's reply denies any union “only through a sharing of dignity and authority” and insists that “we know only one Christ, the Word from God the Father with his own Flesh.”12 Whether Nestorius himself held the view Cyril attacked is still debated by historians, which is why this article describes the error rather than pinning it firmly on the man.
Merging the two natures into one. Eutyches, a monk in Constantinople, was condemned for teaching that after the union Christ's humanity was absorbed into his divinity. Against this Leo, bishop of Rome, wrote the letter to Flavian that the Council of Chalcedon endorsed. The natures stay distinct, Leo argues, and each acts according to what it is: “For each form does what is proper to it with the co-operation of the other; that is the Word performing what appertains to the Word, and the flesh carrying out what appertains to the flesh. One of them sparkles with miracles, the other succumbs to injuries.”13
Chalcedon's four words
The Council of Chalcedon in 451 gathered these boundaries into one definition. It confesses Christ as “perfect in Godhead and perfect in manhood, very God and very man”, “consubstantial with the Father as touching his Godhead, and consubstantial with us as touching his manhood”, and then sets out the union in four negative adverbs:
“This one and the same Jesus Christ, the only-begotten Son [of God] must be confessed to be in two natures, unconfusedly, immutably, indivisibly, inseparably [united], and that without the distinction of natures being taken away by such union, but rather the peculiar property of each nature being preserved and being united in one Person and subsistence, not separated or divided into two persons”
The four adverbs are often quoted in a modern translation as without confusion, without change, without division, without separation. Each excludes one error. Unconfusedly and immutably rule out a mixture in which divinity and humanity blend into a third thing, or one turns into the other. Indivisibly and inseparably rule out two subjects who merely cooperate. The definition does not explain how the union works. It marks the edges of what can be said, and leaves the mystery inside them.
Not every ancient church accepted Chalcedon. The Oriental Orthodox churches (the Coptic, Armenian, Syriac and Ethiopian traditions among them) rejected its wording and prefer Cyril's language of one incarnate nature of the Word. Whether the disagreement is about substance or mainly about vocabulary has been discussed in modern dialogue between these churches and the Eastern Orthodox and Catholic churches. The Chalcedon article and The Seven Ecumenical Councils give the background.
The communication of properties
If there is only one subject in Christ, then whatever is true of either nature is true of that one person. This is the principle theologians call the communication of properties (communicatio idiomatum), and it explains a great deal of Christian speech that can sound strange. It is why Christians can say that God was born of Mary, and that the Lord of glory was crucified, without meaning that the divine nature began to exist or suffered. John of Damascus, in the eighth century, gathered the earlier tradition into a summary:
“For the Lord of Glory is one and the same with Him Who is in nature and in truth the Son of Man, that is, Who became man, and both His wonders and His sufferings are known to us, although His wonders were worked in His divine capacity, and His sufferings endured as man.”
A few lines earlier he says that “the Lord of Glory is said to have been crucified, although His divine nature never endured the Cross”, and in the next chapter he names the principle: “either nature giving in exchange to the other its own properties through the identity of the subsistence and the interpenetration of the parts with one another.”16
The principle is the reason for one of the most disputed words of the fifth century. Cyril defended the title Theotokos on exactly these grounds. The Fathers, he wrote, “ventured to call the Holy Virgin, the Mother of God, not as if the nature of the Word or his divinity had its beginning from the Holy Virgin, but because of her was born that holy body with a rational soul, to which the Word being personally united is said to be born according to the flesh.”17 The title is first a statement about Christ: the one Mary bore is God the Son. The site's article on Mary in the Early Church covers what else the title came to carry.
The same logic applies to the cross. Cyril's twelfth anathema requires the confession “that the Word of God suffered in the flesh, that he was crucified in the flesh, and that likewise in that same flesh he tasted death”.18 The principle is not only Catholic and Orthodox. The Westminster Confession, the Reformed standard of 1646, states it in its own words: “by reason of the unity of the person, that which is proper to one nature is sometimes in Scripture attributed to the person denominated by the other nature.”19 Lutheran and Reformed theologians later disagreed sharply about how far the exchange goes, especially regarding Christ's presence in the Eucharist, but they share the starting point.
Two wills
A seventh-century controversy tested whether the union had been understood fully. Some proposed, as a compromise with those who rejected Chalcedon, that Christ had two natures but only one will or one activity. The objection was that a human nature without a human will is not a complete human nature, and so, by Gregory's principle, the human will would not be healed. The Third Council of Constantinople in 680–681 agreed:
“defining all this 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!) as the impious heretics assert, but his human will follows and that not as resisting and reluctant, but rather as subject to his divine and omnipotent will.”
The Gospels give the clearest picture of this in Gethsemane, where Jesus prays: “Abba, Father, all things are possible to you. Please remove this cup from me. However, not what I desire, but what you desire.”21 On the council's reading, the prayer is not a conflict between two persons. It is the human will of the Son, shrinking from death as a human will does, freely aligning itself with the will he shares with the Father. That freedom does not mean the Son could have sinned. He could not: the one who wills humanly here is the eternal Son, and, as John of Damascus puts it, his human soul “willed of its free-will those things which His divine will willed it to will” (Exact Exposition III.18). His shrinking from death is a natural and innocent human movement, not an inclination to disobey. The Orthodox teaching, and the contrary view of some Protestant theologians, are set out in Could Jesus Have Sinned?
Is it coherent?
The strongest objection is logical. How can one subject be both omniscient and ignorant of the last day, both impassible and suffering? If the same person has contradictory properties, the doctrine seems to state a contradiction.
The classical answer is that the properties are had in different respects. The one person knows all things as God and grows in knowledge as man; is beyond suffering as God and suffers as man. John of Damascus's formula, wonders “in His divine capacity” and sufferings “endured as man”, is an application of this. Whether that answer succeeds is argued by philosophers of religion today, and some Christian thinkers propose other models. But the objection does not show that the doctrine says something like a square circle. It says that one subject has two ways of existing, and asks us to attribute each property according to the nature it belongs to.
A second objection is that the doctrine goes beyond Scripture by using philosophical words. The councils were aware of this. Their answer was that the words were adopted to protect what Scripture says, after purely scriptural formulas had been accepted by people who meant contrary things by them. Leo's letter puts the goal plainly: in Christ the Word “took the form of a slave without stain of sin, increasing the human and not diminishing the divine”.22 That is a summary of Philippians 2, not a replacement for it.
What we can say confidently
The definitions quoted here are secure historical texts, and their meaning is not in doubt: one person, the Son of God, in two complete natures, united without confusion or separation, with two natural wills and two natural operations (energies) in harmony. Catholic, Eastern Orthodox and most Protestant churches accept this Christology; the Westminster Confession states the exchange of properties in its own terms. The terms were coined to exclude identifiable positions: a Christ who is not fully God, not fully human, divided into two subjects, or merged into one nature.
What remains disputed
What Nestorius and Eutyches actually taught. Historians debate how far each held the positions condemned under their names.
The relationship with the Oriental Orthodox churches. Whether their rejection of Chalcedon reflects a real difference of belief or mainly of terminology has been the subject of modern dialogue.
Christ's human knowledge. How to understand texts like Mark 13:32 alongside the divinity of the one who speaks them is read differently by different theologians, ancient and modern.
Philosophical models. Contemporary philosophers defend the coherence of the union in different ways, and some Christian theologians hold forms of kenotic Christology in which the Son limits the use of divine attributes during his earthly life. How far such models fit the Chalcedonian definition is contested.
Notes
- John 1:1, 14. Scripture is quoted from the World English Bible (public domain). ↩
- John 20:28. ↩
- Colossians 2:9. ↩
- Luke 2:52. ↩
- John 11:35. ↩
- Mark 13:32. ↩
- 1 Corinthians 2:8. ↩
- Ignatius of Antioch, To the Ephesians 7 (shorter recension), trans. Alexander Roberts and James Donaldson, ANF 1 (1885), newadvent.org/fathers/0104.htm. ↩
- Cyril of Alexandria, Twelve Anathemas against Nestorius, 2, trans. Henry Percival, NPNF 2nd ser. 14 (1900), newadvent.org/fathers/3810.htm. The anathemas are Cyril's; their formal conciliar status is debated. ↩
- Creed of Constantinople (381), trans. Percival, newadvent.org/fathers/3808.htm. ↩
- Gregory of Nazianzus, Letter 101, to Cledonius, trans. C. G. Browne and J. E. Swallow, NPNF 2nd ser. 7 (1894), newadvent.org/fathers/3103a.htm. ↩
- Cyril of Alexandria, Third Letter to Nestorius, trans. Percival, newadvent.org/fathers/3810.htm. ↩
- Leo the Great, Letter 28 (the Tome), §IV, trans. Charles Lett Feltoe, NPNF 2nd ser. 12 (1895), newadvent.org/fathers/3604028.htm. On Chalcedon's reception of the letter, see the preamble of the Definition (note 14). ↩
- Council of Chalcedon (451), Definition of Faith, trans. Percival, NPNF 2nd ser. 14, newadvent.org/fathers/3811.htm. Brackets are the translator's. ↩
- John of Damascus, An Exact Exposition of the Orthodox Faith III.3, trans. E. W. Watson and L. Pullan, NPNF 2nd ser. 9 (1899), newadvent.org/fathers/33043.htm. ↩
- John of Damascus, Exact Exposition III.3–4. ↩
- Cyril of Alexandria, Second Letter to Nestorius, trans. Percival, newadvent.org/fathers/3810.htm. ↩
- Cyril, Anathema 12, as note 9. ↩
- Westminster Confession of Faith VIII.7, text published by the Orthodox Presbyterian Church. ↩
- Third Council of Constantinople (680–681), Definition of Faith, trans. Percival, newadvent.org/fathers/3813.htm. ↩
- Mark 14:36. ↩
- Leo the Great, Letter 28, §III. ↩
Bibliography
Scripture
- World English Bible. Public domain.
Early and medieval Christian writers
- Cyril of Alexandria. Second and Third Letters to Nestorius; Twelve Anathemas. Translated by Henry Percival. NPNF, 2nd series, vol. 14. 1900.
- Gregory of Nazianzus. Letter 101, to Cledonius. NPNF, 2nd series, vol. 7. 1894.
- Ignatius of Antioch. To the Ephesians. ANF, vol. 1. 1885.
- John of Damascus. An Exact Exposition of the Orthodox Faith. Translated by E. W. Watson and L. Pullan. NPNF, 2nd series, vol. 9. 1899.
- Leo the Great. Letter 28, to Flavian. Translated by Charles Lett Feltoe. NPNF, 2nd series, vol. 12. 1895.
Councils and confessions
- Creed of Constantinople (381); Definition of Chalcedon (451); Definition of the Third Council of Constantinople (680–681). Translated by Henry Percival. NPNF, 2nd series, vol. 14. 1900.
- Westminster Confession of Faith (1646), chapter VIII.
Editorial fact-check ledger
| Claim | Source checked | Confidence |
|---|---|---|
| All quotations from Cyril, Chalcedon, Constantinople III, Leo, John of Damascus, Gregory, Ignatius and Westminster | Copied from the pages in the notes; recorded in the verified bank | Very high (verbatim) |
| Nestorius objected to Theotokos; whether he held the view Cyril condemned is debated | Standard histories; research notes §4.3 item 11 | High for the objection; the interpretation is presented as debated |
| Eutyches was condemned for teaching that the humanity was absorbed into the divinity | Standard histories; Leo's letter was written against his teaching (Chalcedon Definition, preamble) | High |
| The Oriental Orthodox churches rejected Chalcedon's wording and prefer Cyril's language of one incarnate nature | Standard histories | High; the modern dialogue is described only in general terms |
| Monothelitism arose as a proposed compromise with opponents of Chalcedon | Standard histories of the seventh century | High for the general account |
| Lutheran and Reformed theologians disagreed about the extent of the exchange of properties, especially over the Eucharist | Standard histories of Reformation Christology | High for the general claim; no specific texts quoted |
| Contemporary kenotic Christologies exist and their fit with Chalcedon is contested | General description | Interpretation; no individual authors named |