The Incarnation

The Incarnation is the mystery by which the Son of God took a human nature and became man, without ceasing to be God. The word comes from the Latin incarnatio, “taking of flesh”: the eternal Word, by whom all things were made, took flesh from the Virgin Mary, conceived by the Holy Spirit on the day of the Annunciation, to dwell among us. “And the Word was made flesh and dwelt among us, and we saw his glory.” John 1:14

Fully God and fully man

The one who became man is the eternal Son, God born of God. In taking our nature, he kept all his divinity: the fullness of God dwells in him, now in a flesh. “For in him dwelleth all the fulness of the Godhead corporeally.” Colossians 2:9 He is thus at once fully God and fully man.

One single person, two natures

In him two natures meet, the divine and the human. Nature is what a thing is; the person is the one who is, the subject who says “I” and who acts. In Christ, the two natures remain entire and distinct: each keeps what is proper to it, the divinity its omnipotence, the humanity its weakness. They are united in one single subject, the unique person of the Son, who bears them both. It is he, the Word, who is God from all eternity and who, in time, also became man. This union of the two natures in the unique person of the Word, the Church calls the hypostatic union, from the Greek word hypostasis (ὑπόστασις), which designates the person. The Council of Chalcedon confessed it in 451, in a formula that has remained famous: one and the same Christ, acknowledged in two natures, “without confusion, without change, without division, without separation.” The first two words set aside the error that melted the two natures into one, where the humanity would be lost in the divinity, monophysitism (from the Greek monos, “alone,” and physis, “nature”), also called Eutychianism, after the monk Eutyches who taught it. The last two set aside the opposite error, which divided Christ into two juxtaposed persons, Nestorianism, after Nestorius. This confession rested on the letter of Pope Saint Leo the Great, his Tome to Flavian, where the twofold nature was clearly set forth; at its reading, the assembled bishops acclaimed that Peter had spoken through the mouth of Leo. Against both excesses, he remains one single Son, in two whole natures.

Because this subject is one, what each nature accomplishes is attributed to him: the Son of God was born of a woman, suffered, died, and it is God who, in his flesh, has saved us. The Church names this mutual attribution the communication of idioms: the properties of the divinity and of the humanity are said of one and the same Christ. She who bore this one subject brought into the world the Son of God himself: Mary is truly the Mother of God, not that she is the origin of his divinity, eternally received from the Father, but because she is, according to his humanity, the mother of the one who is God. It was Saint Cyril of Alexandria who, against Nestorius, defended this truth: since the Word made flesh is one and the same subject, she who bears him is truly Theotokos, Mother of God; the Council of Ephesus confessed it in 431.

Fully man, save sin

The human nature the Son took is entire and real: a true body, not a mere appearance, and a human soul endowed with intelligence and will. His flesh is not a disguise, and Saint John warns against those who would deny it. “Every spirit that confesses Jesus Christ come in the flesh is of God.” 1 John 4:2 The error that reduces the body of Christ to a pure appearance is called docetism, from the Greek dokein, “to seem.” And because he took a rational soul, and not a mere body that the divinity would animate in place of the soul, he healed in us even the intelligence and the heart: against Apollinaris, who believed that the Word took the place of a soul in Christ, the Church recalls with Saint Gregory of Nazianzus that what was not assumed was not healed. He grew, knew hunger, weariness, sorrow and death. In all things he shared our condition, except sin, of which he was not only preserved but incapable, for there is in him but one single person, that of the Son of God. “one tempted in all things like as we are, without sin.” Hebrews 4:15 His human will freely surrendered to that of the Father, even in the anguish of Gethsemane: “not my will, but thine be done.” Luke 22:42 He therefore has, with his two natures, two wills and two ways of acting: the divine will he shares with the Father, and a human will, true and free, which accords fully with the divine. It is the whole Christ who acts, by the one and by the other. The Third Council of Constantinople confessed it in 681.

Why God became man

The Son became man for us and for our salvation. In becoming man, he first made God visible: no one had ever seen the Father, but the Son, in taking a human face, made him known to us. “he that seeth me seeth the Father also.” John 14:9 He is the very Word of the Father in our flesh. “No man hath seen God at any time: the only begotten Son who is in the Bosom of the Father, he hath declared him.” John 1:18 Of divine condition, he lowered himself to ours, out of love: “Who being in the form of God, emptied himself, taking the form of a servant, being made in the likeness of men.” Philippians 2:6-7 It is as man that he could offer to the Father, in our name, the obedience we refused him, and trace in his flesh the path of holiness; and because this man is God, his gift reopens to us the access to the Father. “it behoved him in all things to be made like unto his brethren, that he might become a merciful and faithful high priest before God, that he might be a propitiation for the sins of the people.” Hebrews 2:17 He became what we are to give us what he is: in taking our nature, he healed it from within and united it to God. Saint Athanasius said it in a word: God became man so that man might become God; the creature does not cease to be a creature, it receives by grace a share in the divine life: “that by these you may be made partakers of the divine nature.” 2 Peter 1:4