The dogmatic clashes of the fourth and sixth centuries will remain incomprehensible until their soteriological aspect is taken into account. During the time of the Arian troubles, St. Athanasius and the Cappadocians strongly insisted that salvation is accomplished as a real meeting between God and man. The Incarnate Word was the true God, not a creature, for only God can reunite fallen humanity with Himself. At the same time, the human nature of Christ was not incomplete, contrary to the teaching of Apollinarius, who believed that the human mind was not perceived by the incarnate Logos, but by the true human nature, "our nature," in all its fullness perceived by the Word, since "that which is not received is not healed, and that which is united to God is saved," wrote St. Gregory of Nazianzus.

In order to understand the subsequent history of the Christological controversy, it is necessary to bear in mind that Nicene Orthodoxy, in the form in which it was formulated by the Cappadocians, was determined by its opposition to both Arius and Apollinaris at the same time. Both taught that in Christ the place of the human mind is occupied by the Logos, and both thought of Christ as one being or one nature. But whereas for Arius unity presupposed the "creation" of the Logos, who is only the supreme intellect (nous), for Apollinaris the understanding of unity resulted in the doctrine of Christ as a "heavenly Man" whose source of life and activity is wholly in the Word. Both Arius and Apollinaris agreed in denying the existence of the human soul in Christ, which allowed both to affirm in Christ the complete unity of the Logos and the flesh: created unity in Arius, heavenly unity in Apollinarius.

However, if the anti-Arianism of the Nicaeans of the fourth century received the form of a positive definition, consubstantiality, which excluded the identification of the Logos with creation, then anti-Apollinarianism remained in a more obscure stage and did not acquire a positive conciliar definition. Throughout the fifth century, anti-Apollinarianism dominated the theology of the Antiochian school, which insisted on the fullness of humanity in Christ. An extreme form of this trend, Nestorianism, went so far as to view Christ's human nature as "adopted man," existing virtually apart from His divine nature. The Alexandrians, on the contrary, remained principled anti-Arians. Their position, though imperfect in that they did not react to Apollinarian tendencies for a long time, had the advantage of always being in agreement with the Nicene definition. Shaped by different types of theological thinking and different exegetical methods, these two schools developed conflicting Christological doctrines.

The harsh critical approach of the Antiochians, such as Diodorus of Tarsus, Theodore of Mopsuestia and Bl. Theodoret of Cyrus, forcing them to adhere to the letter of the Gospel narrative, they set themselves the task of describing the history of our salvation rather than explaining it. Defending a literal interpretation of the books of the Old Testament, the Antiochian theologians strove to draw attention in their interpretations of the New Testament mainly to the historicity of Jesus as the goal and completion of the history of Israel in all the fullness and reality of His human nature. The divine nature of the Word, solemnly proclaimed at Nicaea, appeared to them as a principle, undoubtedly present in Christ, but nevertheless independent in its essence and external manifestations. The theological language of the time did not have adequate terms to express the modern conception of the person as opposed to nature, and since the main concern of the Antiochian school was to defend the full reality of both natures in Christ, it spoke of the "Word who took" human nature and the Man Jesus, the Son of Mary, "received by the Word." Such a distinction was very convenient for exegesis, since it made it possible to interpret various Gospel episodes, referring them sometimes to God, sometimes to Man; moreover, it made it possible to avoid Christological questions about the "death of the Son of God." However, the great Theodore of Mopsuestia was aware that the Antiochian Christology of "the Word who received the Word" and the "man received" was not sufficient to express the confession of the Nicene Creed "in the One Lord Jesus Christ" and could lead to the doctrine of two "subjects" in Christ. Therefore, in all his works he insisted on the unity of the Lord, mistakenly believing that he adequately expressed this unity by the formula: one person (proswpon) and two natures (juseis). Whatever Theodore's meaning of his terminology was still confusing, since the term "person," which combined the divine and human natures of Christ, could also mean a mask in the language of the time. The term "nature" has always indicated a concrete reality and sometimes a personal reality. According to Theodore, the divine reality "dwelt" in the man Jesus, his system excluded the concept of "God the Word, born of the Virgin Mary."

This was the subject of the conflict between Nestorius, a disciple of Theodore, and St. Cyril of Alexandria. In soteriology, the Antiochian school sought above all to defend the fullness of the salvation of human nature in Christ, which Apollinaris denied, because as a man Jesus Christ was wholly received by the Word. One of the most obvious testimonies to the fullness of Immanuel's humanity was His death on the cross. Susceptibility to suffering is an essential characteristic of created human nature, while the nature of the Divine is characterized by impassibility. That is why the great Antiochian teacher Bl. Theodoret rejected the "theopaschism" of St. Cyril and never accepted the expression "God died" on the cross. Theopaschism was for him the surest sign of Monophysitism, which denies the presence of true human nature in Christ, for only man can die, but not God. Even after Bl. Theodoret was reconciled with St. Cyril and accepted the teaching of the Mother of God of Mary with the term "Qeotokos" as an expression of the mystery of the Incarnation in a properly theological, and not only rhetorical sense (the latter was accepted by both Theodore and Nestorius), formally he never said: "God is dead." For him, this would not mean the union of natures, but their mixture, the transformation of human nature into the divine.

This "anthropological maximalism" of the Antiochian school (Florovsky's expression) did not allow for the creation of a coherent concept of redemption. In the Antiochian view, Christ's human nature was autonomous: it also had its own free will, developed and acted independently (albeit in unity with the Word). It was to this human nature that the Antiochians appropriated the merit of our salvation. According to Theodore, the Man Jesus "is assisted by the Word in proportion as He freely affirms Himself in good." From this interpretation of salvation, one can easily draw a conclusion in favor of "humanistic asceticism," which sees man's salvation in his own efforts toward goodness and truth, in imitation of the feat once accomplished by Jesus. Nevertheless, apart from this practical moral tendency, which is inherent in the preaching of the Antiochians as a whole, the latter did not draw all possible conclusions from their Christological theories. In their desire to remain faithful to church tradition, they often returned to the already recognized positions that affirmed Christ as the only Conqueror of sin and death. This fidelity to tradition was combined with a striving for a rational explanation of the Incarnation (in Theodore and especially in Nestorius). But such an explanation required a corresponding metaphysics, which Nestorius clearly lacked. His "rational" approach brought him into conflict with certain expressions of common Christian usage, such as the term "Qeotokos," which immediately made him suspect in the eyes of traditionalists. Nestorius did not have serious theological and philosophical arguments against their criticism. There seems to be no doubt about Nestorius' good intentions, and today some authors believe that he was the most "advanced" theologian of his time, and sometimes present him as an innocent victim of the intolerance of St. Cyril of Alexandria. Such a posthumous apology for Nestorius seems to the author even less convincing than the largely unfounded accusations made by St. Cyril and repeated by subsequent theologians.

In contrast to the Antiochians, St. Cyril of Alexandria sought to emphasize, first of all, that salvation is granted and realized only by God. The power of sin and death cannot be destroyed by the human dignity of the man Jesus. The Word took on human nature, really making it His own. In order to understand Cyril, we cannot but attach special importance to this soteriological aspect of his thought. He asserted that the connection between the divine and the human in Christ consists not merely in the cooperation or even interpenetration of natures, but in unity: the incarnate Word is unique, and there can be no duality in the person of the One Redeemer, God and Man. Salvation consists precisely in the fact that the Word was the subject in all the events of Jesus' human life. It was Him that the Virgin Mary gave birth to: to refuse to call Her the Mother of God means to deny the mystery of the Incarnation, since in Christ there is no one else to whom She could give life except the Word. There are no two sons, there are two births of one and the same Word, who, while by nature unchangeably remaining God, takes on the whole of human nature in His being, in order to restore mankind to its original state, freeing it from sin and death. It was the Word that died on the cross. And the death of God the Word was truly redemptive, while the death of man, even the most righteous, would have remained the ordinary death of human individuality.

St. Cyril expressed a deep Christological intuition within the framework of a still imperfect terminology. In particular, the term "upostasis" was perceived in both Antioch and Alexandria as a synonym for nature (jusis), despite the very accurate use of the word by the great Cappadocians, who used this term in relation to the mystery of the Holy Trinity.

In order to affirm the unity of being, to show that both before and after the Incarnation, the Word is the only Finisher of our salvation, St. Cyril speaks of the one hypostasis or "the one incarnate nature of God the Word" (mia jusis tou Qeou logou sesarkwmenh). The vague term proswpon, used in Antioch to denote the unity of the two natures in Christ, seemed to St. Cyril to be completely unacceptable. Usually he opposed it with the idea of a "hypostatic unity", but because of the synonymous use of the terms upostasis and jusis, adopted by both sides at that time, he was also forced to speak of a "single nature".

For several reasons, the terminology of St. Cyril could not become the basis for the creation of a generally acceptable Christology. First, it did not assign a necessary role to human nature in the matter of salvation. Beginning with Origen, there was a tendency toward "anthropological minimalism," which the Church was forced to restrain, and to which the Monophysites apparently fell a victim. St. Cyril did not realize how much many of his dubious origins were confused by the formula mia jusis tou Qeou logou sesarkwmenh. This formula was borrowed by St. Cyril from a text that he believed to belong to St. Athanasius, but in reality to Apollinarius. The forgery, in which the unsuspecting bishop of Alexandria became an unwitting accomplice, was revealed by Byzantine authors of the sixth century. They, however, did not succeed in preventing the Monophysites from using the ill-fated formula as an anti-Chalcedonian shock weapon. For the Antiochian theologians, who remained faithful to the first anti-Apollinarian polemicists in this, in particular St. Gregory of Nazianzus, formulas such as "the one incarnate nature of God the Word" could not express with sufficient clarity the fullness of the real humanity of Christ. The biblical concept of "flesh" ("the Word was made flesh," John 1:14) in the Greek translation loses its meaning of animate nature and is used mainly as a synonym for the body in its opposition to the soul. The Christology of Apollinaris thus assumed that Christ did not possess a full human nature, but only a human body, and that the place of the rational and immaterial principle in His human nature was taken by the Word, and it was this rational principle that was regarded by the Greeks as the hgemonikon, the governing principle in the human individual. Devoid of human mind (nous), humanity in Christ could not be true human nature, but only an inanimate body in which the Divine Mind dwells.

Although St. Cyril inadvertently used the terminology of Apollinaris in his polemics against the Nestorians, he himself decisively rejected the teaching of Apollinarius. Expressions such as hgemonikon and mia upostasis; seemed to him necessary first of all in order to indicate the identity of the subject between the pre-eternally existing Divine Word and the Incarnate Word. Undoubtedly, St. Cyril fully recognized the fullness of humanity in Christ, the unity of the "two natures." In his first Epistle to Suxens, Cyril lashes out at those who would ascribe to him "the views of Apollinarius" and continues:

If we imagine how the Incarnation took place, we will see that the two natures were united inseparably, inseparably and immutably. At the same time, the flesh remains flesh: it is not the divine nature, although it is the flesh of God, in the same way the Word is God, and not flesh, although in the order of oikonomia He made the flesh His own.

After using such sublime Chalcedonian language, St. Cyril nevertheless returns to his favorite expressions: "We say that there is one Son, as the Fathers said, one incarnate nature of God the Word." It is clear that jusis and upostasis, according to St. Cyril, do not mean "essence." In this case, the essence of the God-Man would be a new essence obtained as a result of the confusion of the Godhead and humanity, the complementary realities from which the hypostasis of the incarnate Word would be composed. This idea of a complex essence, as Diodorus of Tarsus remarks, was the fundamental error of Apollinarius, but we find nothing of the kind in Cyril. Unlike the later Monophysites, however, the great bishop of Alexandria did not require the Antiochians to adopt his own terminology: the phrase "one nature" is not found either in the Anathemas against Nestorius, or in the text of the agreement of 433, which restored unity between the Churches of Antioch and Alexandria.

The victory of St. Cyril in Ephesus (431) resulted not only in the cutting off of the "Nestorian temptation" from Orthodox theology. Its significance lay not only in the affirmation of the truth of the unity of the historical Christ, but also in the proclamation of a positive creative theological conception of the fullness of humanity in Christ, fully assimilated by the Word, a conception affirming the idea of deification, to which all who are "in Christ" are destined. This is what the Council of Ephesus defended when it dogmatized the term "Theotokos" as the name of the Mother of God, because Mary could not be the mother of Christ's "flesh" alone, because this flesh did not have an independent existence, but was truly "the flesh of God." It is in this flesh (kata sarka) that the Son of God suffered, died, and rose again, and through this flesh all redeemed humanity is called to partake of the Holy Spirit. The doctrine of "communion" with the Divinity and the deification of man could not have been created in the context of strictly Antiochian theology.