Those seeking the biblical and theological tools to combat the contemporary restatement of ancient heresies and contemporary denials of orthodoxy would do well to revisit the works of Cyril of Alexandria.
Many evangelical Christians have heard of Athanasius, Augustine, Irenaeus, perhaps even Tertullian or John Chrysostom. Cyril of Alexandria (A.D. 376–444), on the other hand, is not a name with which most Christians are familiar. He was, however, arguably one of the three or four most theologically influential figures in the early church, and regarding Christology, he was perhaps the most influential figure. Cyril was the Patriarch of Alexandria in Egypt from 412 until his death in 444. He had been in this position for sixteen years when Nestorius became Patriarch of Constantinople in 428. He was, therefore, the leader of the church in Alexandria when Nestorius’s criticism of those attributing the title theotokos (“mother of God”) to Mary sparked a controversy whose reverberations would be felt for generations. Cyril’s written responses to Nestorius were to have an influence that he could scarcely have anticipated.
Cyril’s Christology was already established before the controversy with Nestorius, but the controversy forced him to express his views as clearly as possible. In order to understand Cyril’s developed Christology, it is, therefore, helpful to have some grasp of Nestorius’s doctrine. Nestorius’s teaching followed a theological trajectory set by Diodore of Tarsus and his student Theodore of Mopsuestia both of whom advocated, sometimes explicitly and sometimes implicitly, a dual-subject Christology in which the Son of God and the Son of Mary were not identified but instead considered distinct and separate subjects. Nestorius was a student of Theodore of Mopsuestia, and the influence of both Theodore and Diodore can be detected in Nestorius’s theology. He too advocated a dual-subject Christology. This is why he rejected the theotokos. Mary can only be spoken of as the mother of the man Jesus, he argued. She is not the mother of the Son of God. The Son of God and the Son of Mary are distinct in Nestorius’s eyes.
In popular works, Nestorianism is often defined as the idea that Christ is “two persons.” While it is probably inaccurate to attribute this specific idea to Nestorius himself, that which he did teach is equally unorthodox. Nestorius’s emphasis on the difference between the two natures in Christ led him to describe the incarnation in ways that were clearly unsound and profoundly unbiblical. In his first sermon against the theotokos, for example, he writes, “If you want to lift up someone who is lying down, do you not touch body with body and, by joining yourself to the other person, lift up the hurt one while you, joined to him in this fashion, remain what you were? This is the way to think of the mystery of the incarnation. . . .” Nestorius here compares the union of the two natures in Christ to a hug. As this comment makes abundantly clear, Cyril’s response to Nestorius and the theological tradition out of which he came was absolutely necessary if orthodox Christianity was to be preserved.
In direct contrast with Nestorius, Theodore, and Diodore, Cyril of Alexandria insisted on a single-subject Christology. According to Cyril, both Scripture and the Church’s Nicene Creed make it clear that the divine Son, the second Person of the Trinity, is the one subject who became incarnate. He argued that it was this One, the Second Person of the Trinity, who was “made flesh and dwelt among us” (John 1:14). He argued that according to the Nicene Creed, we believe in “one Lord Jesus Christ, the only-begotten Son of God,” and that it is this one, only-begotten Son of God “who, for us men for our salvation, came down from heaven, and was incarnate by the Holy Spirit of the virgin Mary, and was made man, and was crucified also for us under Pontius Pilate.”
When we read the Gospels, according to Cyril, we do not see the Son of Mary saying and doing some things while we see the Son of God saying and doing others. The one we encounter in the Gospels is this one, eternal, divine Son who assumed a true human nature and dwelt among us. Therefore, according to Cyril, it is proper to use the title theotokos, not because the divine nature came into being through Mary, but because the one born to Mary is God incarnate. So, whereas Nestorius proclaimed, “I refuse to acknowledge as God, an infant of two or three months old,” Cyril’s theology was consistent with the worship of the infant Christ described in Scripture (e.g., Matt. 2:1–2).