How to Explain the Incarnation Simply?

Before any image and any nuance, we must hold on to one correct formula. If we retain only one thing, let it be this.

"Without ceasing to be God, he became truly man"

This is the mother-sentence. It contains two affirmations that must always be kept together:

1. He did not cease to be God. In becoming man, the Son did not lose his divinity, did not "empty himself" of what he was, did not change into something else. God remains God.
2. He became truly man. Not a seeming man, not a ghost with a human face, not a god in disguise: a real man, with a real body, a real soul, real tears, a real death.

"And the Word became flesh and dwelt among us, full of grace and truth; we have beheld his glory." — Gospel according to Saint John 1:14^[1]

The Catechism sums up the event in one word: "The fact that the human nature was assumed, not absorbed, means that in the mystery of Christ it was not for all that annihilated."^[2] Assumed, not absorbed: the divinity did not swallow up the humanity, and the humanity did not dilute the divinity. Both subsist, whole, in the same Jesus.

One single person, two natures

The distinction that unlocks everything fits into two words: person and nature. They are everyday words; they only need to be defined simply.

• A nature is what we are: an oak has the nature of a tree, a cat an animal nature, you and I a human nature. Nature answers the question "what?".
• A person is who we are: that "I" who acts, speaks, loves, suffers. The person answers the question "who?".

The Incarnation can then be stated in a sentence of perfect clarity: in Jesus there is one single person — the eternal Son of God — who possesses two natures: his divine nature, which he has from all eternity, and a human nature, which he took in the womb of Mary. That is exactly what the Council of Chalcedon defined in 451, and what the Catechism restates as follows:

"Jesus Christ is true God and true man, in the unity of his divine person; for this reason he is the one and only mediator between God and men." — Catechism of the Catholic Church, § 480^[3]

Hold on to these two words, and all the false formulas fall away by themselves. "Half-man half-God"? False: not two halves of a nature, but two whole natures. "Two Jesuses, the man and the God"? False: not two persons, one alone. The simple rule to repeat: we count one person and two natures, never the other way round.

The theory is laid out. What remains is the hardest part: passing it on. A few pedagogical reflexes make the explanation much clearer.

Start from Christmas, which everyone knows

No need to start with "hypostasis" or "union of natures". The most effective entry point is Christmas, because everyone has an image of it. We can start from the crib and ask a single question: "Who is this baby?" The Christian answer is staggering, and it says it all: this newborn who is hungry, who cries and who depends entirely on his mother is the Creator of heaven and earth. He who holds the universe lets himself be held in two arms. That is where we must start: not from an abstraction, but from a known fact made vertiginous.

"He shall be called by the name of Emmanuel, which means: 'God with us'." — Gospel according to Saint Matthew 1:23^[4]

Insist: God did not "turn into" a man

The most natural trap is to imagine a metamorphosis: God changing into a man the way water changes into ice, ceasing to be what he was. That is the image to defuse straight away. God did not convert himself into a man; he added to what he was from all eternity a human nature. The Son lost nothing by becoming incarnate: he took everything from us, without letting go of anything of himself. The formula to give: "he did not stop being God in order to become man; he remained God while making himself man."

Say both things in the same sentence

The beginner's mistake is to explain the divinity at one moment, then the humanity at another, like two separate files. Yet the Incarnation is precisely that both are true of the same Jesus, at the same time. The right reflex is always to join the two: "It is God who sleeps in the boat", "It is God who weeps before his friend's tomb", "It is God who dies on the cross." This way of speaking — attributing to the unique person of Christ what belongs now to his divinity, now to his humanity — has a technical name, the communication of idioms, but the idea is simple: since there is only one Jesus, what is said of the man and what is said of God are said of him.

Analogies are precious: well chosen, they open the mind in seconds. But none renders the mystery perfectly, and we must always state their limit, lest we teach an error.

The diver who goes down to fetch from the depths

The writer C. S. Lewis compared the Incarnation to a diver: to recover a precious object fallen into the mud, a man strips, dives into the black and cold water, sinks to the muddy bottom, then rises back to the light holding the dripping object^[5]. Likewise, the Son of God went down to the lowest point of our condition — down to death — to rise again carrying with him the human nature he had come to save. Strength of the image: it says the voluntary descent and the purpose (raising up what was lost). Its limit: a diver stays outside the water, whereas the Son truly wedded our nature.

The author who enters his own story

Another very telling image: a novelist can write himself into his story as a character. The author remains fully the author — it is he who holds the pen and brings the whole world of the book into being — and yet he becomes a genuine character who walks, speaks and acts in the narrative, on the same footing as the others. Thus the Word, through whom all things were made, entered as a real character into the history he himself had created. Strength of the image: it admirably preserves that God does not cease to be God (the author) in becoming man (the character). Its limit: a fictional character has no real existence, whereas the humanity of Christ could not be more real.

The king who becomes a servant

The most biblical image is that of the self-emptying: a king who lays down his insignia to take the condition of a servant, without ceasing to be king. That is exactly the movement Saint Paul describes:

"Who, though he was in the form of God, did not count equality with God a thing to be grasped, but emptied himself, taking the form of a servant, being born in the likeness of men." — Saint Paul, Letter to the Philippians 2:6-7^[6]

The Fathers called this self-emptying kenosis (from the Greek kenoô, "to empty"). Beware of the misunderstanding: he did not "empty himself" of his divinity — otherwise he would no longer be God — but he gave up manifesting its glory, accepting weakness, weariness and death. Strength of the image: it comes from Paul himself and says the freedom of the descent. Its limit: a king disguised as a servant is still a king playing at being poor, whereas Christ really became one of us.

The golden rule: "every analogy limps"

Here is the decisive pedagogical point: we must always point out that an image is only an image. The mystery of the union of a divine nature and a human nature in a single person is unique: nothing in creation resembles it exactly, since it is the only case where God and man are one and the same "who". Analogies are stair steps, not the house. We use them to enter, then we leave them behind: what must be retained is never the image, but the correct sentence it helped us understand.

Explaining the Incarnation is above all knowing what must not be said. The main errors are not new: they are the great Christological heresies of the first centuries, which the Church patiently set aside. In plain language, they come down to four.

"Jesus was only an exceptional man"

This is today's most widespread error: Jesus is said to have been a sage, a prophet, a man "filled with God", but not God himself. The ancients called it adoptionism (God supposedly "adopted" a man) or, in another form, Arianism (Christ supposedly a higher creature, but a creature). The simple answer: if Jesus is only a man, then it is not God who came to seek us, and the Gospel collapses. Yet Scripture calls him God: "In the beginning was the Word… and the Word was God" (Jn 1:1). This divinity is treated separately in The divinity of Jesus.

"Jesus was only pretending to be a man"

The opposite error, older, is called docetism (from the Greek dokeô, "to seem"): God supposedly only took on the appearance of a man, like a costume, without truly suffering or dying. Many commit it unknowingly by saying "God disguised himself as a man". Yet Saint John wrote a sentence expressly to bar it:

"By this you know the Spirit of God: every spirit which confesses that Jesus Christ has come in the flesh is of God." — First Letter of Saint John 4:2^[7]

The body of Christ was no disguise: he was hungry, thirsty, sleepy, and he died for good. To deny that is to deny the Cross — and therefore salvation.

"Jesus is half man, half God"

This is the most instinctive error, and the most stubborn. We picture a mixture, as when two liquids are mixed to obtain a third thing — a demigod out of mythology. The ancients called it monophysitism (a single "fused" nature). The Council of Chalcedon settled it with four famous adverbs: the two natures are united "without confusion, without change, without division, without separation"^[8]. Saint Leo the Great, whose letter carried authority at the council, had put it in a limpid formula:

"Each nature fulfils in communion with the other what belongs to it: the Word performing what belongs to the Word, and the flesh carrying out what belongs to the flesh." — Saint Leo the Great, Tome to Flavian (449)^[9]

Jesus is therefore neither 50% God nor 50% man: he is 100% God and 100% man, without mixture. The right image is not the blend, but the addition of two totalities in a single "who".

"Mary is mother only of the man Jesus"

A last frequent error, and it follows from the previous ones: we would like Mary to have given birth only to "the human part" of Jesus. But we do not give birth to a nature, we give birth to a person — and the person she brought into the world is the Son of God. That is why the Church calls her "Mother of God" (Theotokos), not to make her divine, but to affirm that her child is truly God. This delicate point, and the objection that goes with it, are treated in Why is Mary called Mother of God?.

To explain the Incarnation, a few well-chosen verses beat a flood of references. Three say it all.

"The Word became flesh" (John 1:14)

This is the verse of the Incarnation, once read at the end of every Mass. It says the whole movement: the Word (the eternal Son, "through whom all things were made") becomes flesh (our most fragile condition, which is born and which dies). Note that John does not say "the Word became a man" as one becomes an adult, but "became flesh": he wedded even our frailty.

"He emptied himself, taking the form of a servant" (Philippians 2:6-7)

This passage^[10], probably a very ancient hymn sung by the first Christians, gives the meaning of the Incarnation: a descent out of love. It is precious for showing that God became man neither out of necessity nor out of play, but by a free act of coming down to us. It is the perfect antidote to the idea of a distant, indifferent God.

"God with us" (Matthew 1:23)

The name Emmanuel^[11] sums up the existential stakes: through the Incarnation, God is no longer only above us or facing us, but with us, in our flesh, on our side. This is the verse that touches the heart, where the first two touch the mind.

Sooner or later comes the real question: "But why? Why would God go to such trouble?" The Incarnation is no whim: the Catechism gives four reasons for it, which can be put very simply.

To save us

First, to reconcile us with God^[12]. God himself had to come and repair what man could not repair alone; and he had to do it as man, from inside our humanity, so that it would truly be ours that was raised up. This is the direct link with the Cross: he became man so that he could die, and he died to save us. The detail of that "why die" is developed in Why did Jesus have to die?.

To show us God's love and to give us a model

Next, so that we may know God's love^[13]: in Jesus, God's love ceases to be an abstract idea; it has a face, hands, a voice. And to be our model of holiness^[14]: God no longer only tells us how to live, he comes to live it before us, at our own scale. "I have given you an example," Jesus will say.

So that man may share in God's life

Finally, the highest reason, the one the Fathers repeated like a shout of joy: God became man so that man may share in God's life. This is the famous admirabile commercium, "the marvellous exchange": he takes our humanity to give us his divinity.

"The Word became flesh to make us sharers in the divine nature. […] For the Son of God became man so that we might become God." — Catechism of the Catholic Church, § 460, quoting Saint Athanasius^[15]

This sentence of Saint Athanasius, which must above all not be understood as if we became gods by nature, says the incredible destination of the Incarnation: God makes himself our brother to make us, by grace, sons of God.

What remains is to move from the blackboard to real conversation. Here are two adaptable "scripts".

To a child

With a child, start from the crib: "Do you see that little baby? That is the greatest secret of Christmas: that baby is God who made himself tiny to come and join us. He could have stayed in Heaven, immense and invisible. But like a dad who kneels down to speak at his child's level, God made himself a little man to be very close to us, so that we can see him, hear him and love him. He did not stop being God: he also became a man, like us." The image of the dad bending down says the essential without a single technical word.

To a doubting adult

With a sceptical adult, do not start by asking him to believe, but first make him understand what is being affirmed — for many reject a caricature. We can say: "Christians do not say that God turned himself into a man, nor that a half-god appeared. They say something more precise: the author of the story entered his own story as a character, without ceasing to be its author. The question is therefore not 'can God change himself into a man?', but 'can God add a human life to himself?' — and nothing prevents him from doing that." In this way we move the objection: we do not defend the absurd, we present the unheard-of. The very possibility of the Incarnation, and the answer to the objections, are treated in Is it possible that God became incarnate?.

These distinctions might seem to concern only theologians. It is the reverse: everything in Christian life depends on them. If God did not truly become man, then he did not truly join us, truly understand us, truly save us; he remains a distant God watching from afar. But if he became one of us, then none of our distress is foreign to him: he knew weariness, betrayal, fear, death. The Incarnation is what lets us say that, from now on, God knows what it is like.

"A man of sorrows, and acquainted with grief." — Book of Isaiah 53:3^[16]

Like the Servant announced by Isaiah, he did not hesitate to go down to the lowest condition — dust and ashes — so that man would not despair. The whole logic of Christmas lies in this descent: God comes down to us so that we may go up to him.

That is why explaining the Incarnation simply, but without betraying it, is no school exercise: it is announcing the news that changes the face of God. No longer only "God exists", but "God has come, and he is one of us".

• Is it possible that God became incarnate and died on a cross? — the complete case: metaphysical possibility, the Muslim objection, the historical proof of the crucifixion.
• The divinity of Jesus — the first truth the Incarnation presupposes: why Jesus is true God.
• Why is Mary called Mother of God? — the Marian consequence of the Incarnation: we are mother of a person, not of a nature.
• Why did Jesus have to die? — what follows the Incarnation: he became man so that he could give his life.
• Why is Christmas celebrated on 25 December? — the feast of the Incarnation and the date of its celebration.