The Evangelist had previously informed us of the unhappy situation that prompted the Word to come to us in the flesh, for though He made the world and was in the world, “the world knew him not” (v. 10). Then he elaborated upon the benefits we received from His coming: “to all who received him, who believed in his name, he gave power to become children of God” (v. 12). Now he shows how the Word came: “And the Word became flesh” (Jn 1:14a). To say that “the Word became flesh” is to affirm what was said previously: “He came to his own home” among “his own people” (v. 11). The reason the Evangelist elaborated on “He came to his own home” by specifying that He “became flesh” was to dispel any suggestion that the coming of the Word was for Him simply a change of venue. Instead, he makes it clear that His coming was not the termination of a movement through space, but a new manner of existence. Now the Son of God, a divine person having the divine nature, assumed a human nature by means of His incarnation in the womb of the Virgin Mary.

St. John Chrysostom asserted that the reason why Christ is able to give us the “power to become children of God” (Jn 1:12) is because He Himself “became flesh,” as St. Paul explained: “when the time had fully come, God sent forth his Son, born of woman, born under the law, to redeem those who were under the law, so that we might receive adoption as sons” (Gal 4:4-5).

St. Augustine offered another interpretation, following upon the belief that with God all things are possible. He reasoned that if God is willing and able to condescend to become man, then surely He can raise up man, giving to those who receive Him and believe in Him the “power to become children of God.”

This succinct phrase, “The Word became flesh,” has often been misinterpreted to mean that some part of the Word was transformed into human flesh, as flour is transformed into bread. But this cannot be, for God is eternal and immutable. He said, “I the Lord do not change” (Mal 3:6). In his commentary, St. Thomas looks at five errors in detail: Arianism, Apollinarianism, monophysitism, Manicheanism, and Nestorianism.

One such error was propagated by the priest Arius of Alexandria (ca. 270-336), who believed that there was no human soul in Christ, but that the Logos (the Word of God) stood there in its place. Arius’ error can be refuted in three ways. First, we note that Christ’s behavior at times suggests that He had certain affections like us. For example, we read that “He began to be sorrowful and troubled” (Mt 26:37). Emotions do not properly exist in pure spirits, nor in the flesh alone; but rather, they are affections of the soul. Second, Christ Himself affirmed that He has a human soul when He said, “My soul is very sorrowful” (Mt 26:38). Third, Aristotle stated that a corporeal substance consists of form and matter, where form gives shape to indefinite matter. The soul is the form of the human body. An angel cannot be the form of a body, for an angel, according to its nature, is a purely spiritual being without a body. The same is true of the Word of God, Who is pure spirit. Thus, for Christ to be fully human and to have a true human nature, He must have a human soul to inform His human body. The flesh that Christ assumed in the Incarnation was a human body with a human soul.

A second error, similar to that of Arius, was put forth by Bishop Apollinaris of Laodicea (310-90), who was right in asserting that the Word assumed flesh with a human soul, but went astray in asserting that His soul was only a sensitive soul, not an intellectual soul, and that the Word stood in place of Christ’s human intellect and will. We can rebut Apollinaris in three ways. First, one may admit that his position is somewhat an improvement over Arius’ position, for at least it explains how Christ could experience human emotions, namely, with a sensitive human soul. Yet Apollinaris leaves Christ’s humanity incomplete, for his Christ lacks a human intellect and will. And if He lacked a human will, how could He conform His will to the divine will? How could He be obedient to the Father unto death? How could His suffering and death merit Him resurrection and merit fallen man the grace of salvation? His meritoriousness lies not in the fact that Christ as God wills our salvation, but in the fact that Christ as man conformed His human will to the divine will in perfect obedience to the Father. Second, we read that Jesus “marveled” at the faith of the centurion (Mt 8:10). To marvel is a state of wonder that arises in the intellect when one desires to understand the cause of an effect one observes. Wonder is not found in the sensitive soul, for wonder pertains to the intellect. But, the Word cannot marvel, for He knows all things and the causes of all effects. Therefore, the Word of God did not stand in place of Christ’s human intellect. Third, every human body is informed by a human soul, which is a rational intellectual soul by nature. If Christ has a human body, then it follows that His body must be informed by an inte llectual human soul.

In STh III, 5, 3. St. Thomas demonstrated the falsity of Apollinarianism in three ways. First, St. Thomas noted that Christ mentioned His soul in Mt 26:38. Apollinaris, not surprisingly, took this metaphorically, as even Is 1:14 speaks of the “soul” of God. But Augustine showed how the evangelists did not intend this metaphorically, for they wrote elsewhere that Jesus was angry, sad, and hungry. Second, if Christ did not assume a soul, then either (1) He thought that the human soul is without stain of original sin, and hence, not in need of a remedy, or (2) He thought it unsuitable for Him for assume a soul, or (3) He was unable to heal the human soul. But this would render the Incarnation practically useless, and it is a blasphemy to denigrate the power of God. Third, the body is informed by the soul (Aristotle, De Anima ii, 9). Where there is no form, there is no body. Where there is no human soul, there is no human flesh. As form and matter must be present in every corporeal substance, soul and body must be present in every human body. Therefore, Christ, Who truly has a human body, truly has a human soul; and His human nature includes both body and soul.

A third error arising from Jn 1:14a originated with Eutyches (378-454), the archimandrite (president) of the monastery at Nicerta on the outskirts of Constantinople. Eutychianism, also known as monophysitism, reared its head at the Council of Ephesus (431) in reaction to Nestorianism, which asserted there are two persons in Christ. Nestorius (386-451) became archbishop of Constantinople in 428, but was deposed in 431 by the Council of Ephesus, on account of his heresy. Eutyches, in his zeal to refute Nestorian dualism, over-reacted by asserting that the human nature of Christ was totally absorbed by the divine nature, “dissolved like a drop of honey in the sea,” so that Christ was left with only a divine nature. In November of 448, Patriarch Flavian of Constantinople called a diocesan synod, which formally charged the elderly monk Eutyches with heresy. Eutyches failed to convince the synod otherwise, and was excommunicated and deprived of his position as archimandrite. The synod declared it a matter of faith that, after the Incarnation, Christ consisted of two natures united in one hypostasis (person). Eutyches appealed to the Byzantine Emperor Theodosius II (408-50) through the eunuch Chrysaphios, who was Eutyches’ godson and Theodosius’ chief minister at Constantinople. Chrysaphios wrote to Rome and elsewhere to drum up support for his godfather Eutyches. Patriarch Dioscorus of Alexandria (444-51) responded favorably and defended Eutyches, believing that the monk was valiantly fighting a battle against Nestorianism, a particularly virulent heresy that refused to die, despite its condemnation by the Council of Ephesus. Nestorius’ main opponent had been Patriarch Cyril of Alexandria (d. 444). Dioscorus had been Cyril’s deacon during the height of the Nestorian controversy, and Dioscorus succeeded St. Cyril as patriarch upon the saint’s death. Eutyches wrote to Pope Leo I in the spring of 448, portraying himself as a defender of the faith. But just as Eutyches failed to convince Flavian’s synod, he failed to convince the pope. A few months later, in 449, Pope Leo responded in his Dogmatic Letter to Flavian (Tomus Leonis, the Tome of Leo), supporting Flavian’s condemnation of monophysitism. The Tome is most significant in the history of Christology, for it fully defines what we believe about the hypostatic union and the Incarnation. The Eastern Emperor Theodosius ignored both the Tome and Patriarch Flavian’s condemnation of monophysitism; he instead convoked a regional ecclesiastical council, which met in Ephesus in August of 449, with some 150 bishops in attendance, almost all of whom were from the East. This synod reinstated Eutyches’ priestly and monastic office and refused to read Pope Leo’s Tome at the proceedings. The pope responded by condemning the synod and its Acts, calling it the Latrocinium (Robber Council) of Ephesus. He asked the emperor to hold a new synod in Italy, but Theodosius, not surprisingly, refused. East and West were deadlocked in a power struggle until Theodosius suddenly died in 450. The Eastern Roman Empire fell into the hands of his sister Pulcheria, who was opposed to monophysitism. She appointed her husband Marcian Emperor of the East, and he expressed to Pope Leo a willingness to call a new council in the East should the pope desire it. Accordingly, on October 8, 451, a general council was convened at the Church of St. Euphemia, outside of Chalcedon, which is across the strait from Constantinople. There were some 630 bishops in attendance; almost all were from the East. Chalcedon received the papal legates and accepted Pope Leo’s Tome in its entirety. At the second session (October 10), the bishops declared that the faith contained in the Tome was the faith of the Fathers and of the Apostles. They further declared that through Pope Leo, Peter himself had spoken. The dogmatic decree of Chalcedon was published at the fifth session (October 22). It summarized the teaching contained in the lengthy Tome. With the closing of Chalcedon, the essential elements of Christology had been defined by the majority of Eastern bishops and confirmed by the pope.

One might ask why the Evangelist wrote, “the Word became flesh,” rather than, “the Word assumed a rational soul”? He did this for four reasons. First, he wished to refute the Manichaeans, who believed that the Word did not assume real flesh, but only the appearance of human flesh. They believed that all material things, including the human body, were created by the devil; and so, they could not envision the supremely good Word in human flesh. To rebut them, St. John specified that “the Word became flesh,” that is, truly human flesh. In a like manner, St. Luke shows that the resurrection was not an apparition; he quotes Christ saying to His disciples, “See my hands and my feet, that it is I myself; handle me, and see; for a spirit has not flesh and bones as you see that I have” (Lk 24:39). Second, St. John wished to demonstrate the great kindness God showed to men. It was a great kindness for God to assume a rational soul, but an even greater kindness to assume flesh, for the human soul, on account of its ability to reason and the fact that it is a spiritual creature, is more like God, Who is pure spirit, than the human body, which is altogether corporeal. For God to condescend to assume a spiritual human soul is one thing, but to assume corporeal human flesh is another. St. Paul remarked, “Great indeed, we confess, is the mystery of our religion: He was manifested in the flesh” (1 Tm 3:16). Third, the Word assumed both body and soul to distinguish the hypostatic union from other occasions in which God united Himself in some way with holy men, for example, when Wisdom “passes into holy souls and makes them friends of God, and prophets” (Wis 7:27). Fourth, the Evangelist referred to human flesh because of its relevance to man’s fall and to his restoration, for Christ came in the flesh to repair the weakness of sinful flesh. He assumed human nature to repair it, for as St. John Damascene (John Mansur of Damascus, ca. 645-749) wrote, “what was not assumed is not curable” (De Fide Orth. 3, 6). The disobedience of the first Adam was remedied by the perfect obedience of the Second Adam: “as in Adam all die, so also in Christ shall all be made alive” (1 Cor 15:22). St. Paul remarked, “God has done what the law, weakened by the flesh, could not do: sending his own Son in the likeness of sinful flesh and for sin, he condemned sin in the flesh, in order that the just requirement of the law might be fulfilled in us, who walk not according to the flesh but according to the Spirit” (Rom 8:3-4).

One might ask why the Evangelist wrote, “the Word became flesh,” rather than, “the Word assumed flesh”? We can answer this in two ways. First, St. John used this language to exclude the error of Nestorius, who thought that Christ consisted of two persons, two sons, one being the Son of God, the other being the son of Mary. Now, one suppositum cannot be predicated of another, and one suppositum cannot become another suppositum, for the suppositum is that which underlies a substance and supports its accidents. Accordingly, if the Person of the Word is different than the Person of Jesus, then the Word could not have become flesh, for one person cannot be predicated of, or become, another. Second, St. John used “became,” rather than “assumed,” lest anyone think that God came upon Jesus in the same way that He came upon the prophets, lifting them up to speak on His behalf. To “become” something is to be the thing itself, to have its nature, whereas one can “assume” a thing without taking its nature.

One might ask how the Word of God is man? He is not human nature itself, but has a human nature like any other man. He is not a human person, a human suppositum. Rather, He is a divine person with two complete natures, which is to say, He is a divine suppositum united to a human nature. A relation between God and man necessitates a change on the part of man, but not on the part of God, for God is immutable. The Incarnation brought about no change to the divine nature of the Word, for His union with human flesh is a relation, and although relations imply change in human beings, they do not imply a change in God. In the Incarnation, nothing changed on the part of God, but something changed on the part of man: mankind gained a savior, and fallen human nature was restored.

The Evangelist added, “and dwelt among us” (Jn 1:14a), to dispel any notion that the Word’s divine nature was transformed into a human nature, for that which “dwells among” something is distinct from that among which it dwells. The Word dwells with us, that is, in our human nature, yet He retains the fullness of His divine nature. If His divine nature were transformed into human nature, then we could not say that He “dwelt among us,” for whatever is converted into something else, ceases to remain distinct in nature from that into which it is converted. Whatever dwells in a thing is not distinct from that thing. In speaking of the “temple of his body” (Jn 2:21), Christ distinguished His two natures, for His divine nature is the temple of His divinity, and His human nature is the dwelling place wherein lives the Divine Person of the Word.

Nestorius misunderstood the phrase, “and dwelt among us.” He thought that it implies that there are two persons in Christ. He believed that the Word was united to human nature by an indwelling of grace, which is not a substantial union, but a moral union for a specific purpose. And if it is not a substantial union, then the Son of God is not truly a man, but is merely in a moral relationship with men. We can respond to Nestorius in two ways. First, St. Paul suggested that the hypostatic union is more than a moral union, for it involved an emptying, for the Word “emptied himself, taking the form of a servant, being born in the likeness of men” (Phil 2:7). He Who was in the “form of God” took “human form” (Phil 2:6, 8). God does not empty Himself by dwelling in a creature by grace, else we would read that the Father and Holy Spirit were also emptied. Rather, the Son alone emptied Himself, because the Son alone assumed human nature and became man. Second, Christ is one person, not two, for if Christ were two, it would have been presumptuous for Him to claim, “before Abraham was, I am” (Jn 8:58) and “I and the Father are one” (Jn 10:30), for while it is true of a divine person to say these things, it is not true of a human person.

Why did the Word choose to dwell among us? First, He dwelt among us so that His witnesses could say that they actually “ate and drank with him after he rose from the dead” (Acts 10:41). Thus, their credibility would be increased. Second, He not only willed to assume a human nature, but to dwell among us sinners in order to better draw us to Himself. “God so loved the world that he gave his only Son, that whoever believes in him should not perish but have eternal life” (Jn 3:16). So great is the love of the Shepherd for His lost sheep!