One Person, Two Natures
How can one person be both God and man?
Main teaching: De fide
The big question
Lessons 5.1 and 5.2 showed that Christ is fully God and fully human. But is he then two persons, a divine one and a human one, working closely together? Or is he a mixture, half God and half man? And if he is one person, how can the same person be eternal and also born in Bethlehem?
What the Church teaches
Christ is one divine Person, the eternal Son, who has two natures, divine and human. The union of the two natures in the one Person is called the hypostatic union, from the Greek hypostasis, “person” (Ephesus, 431; DH 250–252; CCC 466).
The two natures remain distinct, “without confusion, change, division or separation” (Chalcedon, 451; DH 301–302; CCC 467).
So Mary is truly the Mother of God, because the one she bore is the divine Person of the Son (Ephesus; DH 251–252; CCC 495). Unit 7 returns to this.
How sure is this? De fide. See CCC 464–469.
Where it comes from
Scripture. The New Testament speaks of one and the same subject as both divine and human. “God sent forth his Son, born of woman” (Galatians 4:4): the eternal Son is the one born. The hymn in Philippians says that the one who “was in the form of God” is the one who “emptied himself, taking the form of a servant”, and “became obedient unto death, even death on a cross” (Philippians 2:6–8). St Peter tells the crowd in Jerusalem that they “killed the Author of life” (Acts 3:15), and St Paul that the rulers of this age “crucified the Lord of glory” (1 Corinthians 2:8).
The early Church. Two great councils settled the question, each against an opposite error.
- Ephesus (431). Nestorius, Archbishop of Constantinople, objected to calling Mary “Mother of God”. He spoke of the man Jesus and the divine Word as closely joined, but in a way that left them two subjects. St Cyril of Alexandria answered that the Word himself was born, suffered and died in the flesh. Ephesus agreed with Cyril.
- Chalcedon (451). Eutyches went to the opposite extreme: after the union, he said, Christ’s humanity was absorbed into his divinity, leaving one nature. Pope St Leo the Great sent a letter, the Tome, explaining that each nature keeps its own properties and acts in communion with the other. When it was read at Chalcedon, the bishops are reported to have cried out, “Peter has spoken through Leo!”
How theologians explain it
Two errors, one truth.
| Nestorianism | Monophysitism | The faith of Chalcedon | |
|---|---|---|---|
| Persons | Effectively two: a man and the Word | One | One: the divine Son |
| Natures | Two | One (the human absorbed into the divine) | Two, complete and distinct |
| Mary | Mother of the man Jesus | Mother of God | Mother of God |
| The danger | Christ falls apart into two | Christ’s humanity disappears | Both kept |
Union in the Person. The two natures are not united by mixing, nor by two persons agreeing. They are united in the one Person who possesses both. The human nature of Christ never existed on its own as a separate human person; from the first moment of its existence it was the humanity of the Son. So when Jesus speaks, eats, weeps or dies, it is always the Son of God who does so, in his human nature.
How to speak about Christ. Because there is one Person, whatever can be said of either nature can be said of the Person. This is called the communication of idioms (Summa III, q. 16). It gives rules for speaking accurately:
| Correct | Why | Incorrect | Why |
|---|---|---|---|
| ”God was born of Mary” | The Person born is God | ”The divine nature was born” | Natures are not born; persons are |
| ”God died on the Cross” | The Person who died is God, in his human nature | ”The divinity died” | God’s nature cannot die |
| ”This man is the Creator” | The Person of this man is the eternal Word | ”The humanity is the Creator” | The human nature is a creature |
A mystery, not a contradiction. As with the Trinity, Chalcedon does not explain how God and man are one, but it states the truth precisely enough to rule out the errors. Pohle sums up the theologians’ view: the dogma is above reason, but reason can show it is not against reason.
Healing old divisions. Some ancient churches rejected Ephesus or Chalcedon, partly over words and translations. In recent decades the Catholic Church has signed joint declarations with several of them, recognising that they confess the same faith in Christ, true God and true man, in different terms. Examples are Pope Paul VI with the Coptic Pope Shenouda III in 1973, and Pope John Paul II with the Assyrian Church of the East in 1994.
Philosophy bridge
The philosophy course’s distinction between nature and person is what makes Chalcedon possible. Nature answers what: divine and human. Person answers who: the Son. In the Trinity, one nature belongs to three Persons; in Christ, one Person has two natures.
What the Church does not claim
- Not that Jesus is half God and half man. He is fully God and fully man.
- Not that Jesus switches between being God and being man. Every act is the act of the one Person, and his two natures are always both present.
- Not that “God died” means God ceased to exist. The Son died in his human nature: his human soul was separated from his body. His divinity never ceased.
- Not that there is a human person inside Jesus alongside the divine one. His humanity is complete, but it is the humanity of the divine Person.
Check your understanding
- What is the hypostatic union?
Show answer
The union of the divine and human natures in the one divine Person of the Son. “Hypostatic” comes from hypostasis, “person”.
- What did Nestorius and Eutyches each teach, and which council answered each?
Show answer
Nestorius separated Christ into two subjects and refused to call Mary Mother of God; Ephesus (431) answered him. Eutyches said Christ’s humanity was absorbed into one divine nature; Chalcedon (451) answered him.
- Write out Chalcedon’s four words for how the two natures are united.
Show answer
Without confusion, without change, without division, without separation.
- Is it correct to say “God died on the Cross”? Is it correct to say “the divinity died”? Explain.
Show answer
“God died on the Cross” is correct, because the Person who died is God, dying in his human nature. “The divinity died” is incorrect, because the divine nature cannot die; only the human nature underwent death.
- Why is Mary called Mother of God, and not only mother of Christ’s human nature?
Show answer
Because a mother is mother of a person, not of a nature, and the Person she bore is the divine Son. So she is truly the Mother of God.