C. S. Lewis once said that if the incarnation happened, “it was the central event in the history of the earth.” What is the incarnation? And why has it been such an important area of theological consideration since the earliest days of Christianity? The term ‘incarnation’ may be defined as “a person who embodies in the flesh a deity, spirit, or quality.” For the Christian tradition, the man who has been understood as deified has been Jesus of Nazareth; but the Christian claim of Jesus as God, not merely as one who embodied God, historically presented a plethora of questions to the early Christian theologians.
In determining what the incarnation means for Christians, the Early Church Fathers sought to determine more concerning the person Jesus. Maurice Wiles writes that “the heart of Christian faith is the person of Christ and what God has done in him.” The orthodox Christian Church has always professed monotheism based upon the Jewish tradition and the scriptures. Given this monotheistic belief however, the early Church viewed Jesus not as a simple messenger of God, but worshiped Him as the Son of God. This is especially evident in the writing’s of Irenaeus, who refers to Jesus as “the Word, the Son of God.” 
Thus the Early Church, in confessing Jesus as the Son of God, needed to determine exactly what was meant by this profession. As Wiles points out, this confession led to some serious questions: “How without simply abandoning the idea of God’s eternal changelessness could he describe the divine action in creation and in history?” As a possible solution to the problem of explaining the incarnation, early theologians such as Tertullian turned to philosophy. Splitting Jesus Christ into two ‘parts’, the human Jesus and divine Christ, was suggested. This idea was rejected by the Fathers, especially by Irenaeus, who quotes the Gospel of John (20:21), “these things are written that ye might believe that Jesus is the Christ, the Son of God”, in defense of Jesus’ humanity and divinity. Yet there are seemingly problems with this view, as St. John also writes “that which is born of flesh is flesh, and that which is born of Spirit is spirit” (John 3:6). Tertullian apparently recognized this dilemma, and affirms the duality of Jesus without much explanation of the combination of flesh and logos.
Within the writings of Origen there is found the first serious theological approach to answering the question of what was meant by the incarnation of Christ Jesus. Origen suggested the idea that Christ had two natures, a ruling divine nature and a less influential human nature. Origen’s basic idea of two natures is professed even to this day in Christianity, though his other belief that the eminence of the human soul of Christ fell into disrepute. If Jesus had a human soul which was in perfect fellowship with God and was in contrast with the logos as Origen believed, then questions result. First, the question of two separate persons united in Jesus arises: Is there one perfect human and one separately divine within the man Jesus? If so, did the sacrifice on the cross only involve the man Jesus? Was “Christ crucified” as was the confession? Second, if the emphasis remains on the human soul of Jesus, could that not mean that Jesus was simply a perfect man and not truly God in any meaningful way?
The importance of answering the incarnation question became even more significant with the rise of Arianism in the East. If Arius was correct, and Jesus was only God in some secondary categorization, then the problem of the incarnation becomes significantly less: no longer would Christianity be proclaiming Jesus as fully God, but as fully man with the power of God –much easier to assert from a philosophical position. To many non-Arian Antiochene theologians during the fourth century, the importance of Christ’s human soul was paramount. If Christ is not human, then how can one account for the salvation of man and the emotions that Jesus seems to display in the gospels? As an alternative confession, there was the importance placed on the divinity of Christ and the Word experiencing humanness which Athanasius and the Alexandrians professed. Athanasius did not believe that the Son has ceased in any way to be God when He came to earth. “In becoming incarnate the divine Word did not abandon any of his divine attributes; the suggestion is dismissed as absurd. But he did not assume in addition to them the limitations of his adopted human nature.” 
Between the Council of Nicaea (325 AD) and the Council of Chalcedon (451 AD), many controversies erupted from the Alexandrian and Antiochene positions on the person of Christ. The Council of Constantinople (381 AD) condemned the belief of Apollinarius that Christ only had one will, that of the divine. While the Church believed that Christ had a divine will, there was too much scriptural and philosophical support for the position that Christ had a human will as well. How else can one explain Jesus’ prayer in Gethsemane, “Not my will, but yours, be done” (Luke 22:42), and other verses that seem to indicate that Christ had a human will? For God to be the redeemer of man, He needed to include full humanity as Irenaeus and Tertullian had emphasized years before.
The Council of Ephesus (431 AD) condemned an opposite belief, that held by Nestorius: the denial of the divine will of Christ. Nestorius held to the beliefs professed by his teacher, Theodore of Mopsuestia, who will holding to the divinity of Christ, placed special emphasis on the capacity of the human will. As Athanasius had feared, Theodore and Nestorius took the full humanity of Christ to mean that instead of being fully God, He had received something along the lines of ‘inspiration’ from God much like a prophet or saint would, though to a greater degree. Nestorius was refuted by Cyril of Alexandria, who used the words of Christ to convict him. How does a Christ who is not fully divine say to his disciples that “I came from the Father and have come into the world, and now I am leaving the world and going to the Father” (John 16:28)? Historically, both the Alexandrian and Antiochene positions were shown to have weaknesses in their views of the incarnation of Christ. What then is the answer concerning the incarnation?
Gregory the Theologian’s maxim, “What is not assumed is not healed” became the focal point for Christian thinking concerning the Incarnation. As Wiles writes, “The important thing about Christ therefore was not that the Word had become a man but that the Word had assumed humanity in order to save” man. While the Alexandrian and Antiochene positions could not themselves be formed into a single coherent picture, they could agree on common ground as they did in the “Chalcedon Definition.” This definition reads that Christ is “truly God and truly man, the same rational soul and body… acknowledged in two natures, without confusion, without change, without division, without separation.” While this philosophically and soteriologically derived definition seems to be a clear compromise, it emphasized the boundaries concerning the person of Christ for the Orthodox Christian faith, outlawing Nestorian and Apollinarian heresy.
Thus the Church did not find an actual answer to the question regarding the incarnation of Christ; the Fathers only set boundaries concerning the terms which may be found orthodox concerning the belief in the full humanity and full divinity of Jesus Christ. Wiles ends his chapter on the incarnation in The Christian Fathers with a question: “How can this Jesus, with all the marks of manhood upon him, be the one in whom God saves the world?” The Fathers wrestled with the philosophical answer to this question and their reasoning is helpful. It seems unwise to rid ourselves of the conclusions of the Fathers who have gone before us, as Wiles himself later suggested in The Making of Christian Doctrine. To what then can we appeal for guidance?
Wiles appeals to three disciplines for forming a proper understanding of Christ: Scripture, Worship, and Soteriology. From Scripture, we can see that the view of Christ as God and man is a bit ambiguous at times. Yet it is clear that the scriptural Jesus is a man –He was born (Luke 2), eats (John 4), weeps (John 11), and walks like a normal human being. Similarly, Jesus is clearly not just a man –He performs miracles (Mark 9), raises the dead (John 11), and does not rebuke Peter when he calls Him the Son of God (Matthew 16). Scripture seems to indicate that Jesus of Nazareth was both God and Man. Concerning worship, evidence exists that the man Jesus was worshiped as God in the earliest Christian Churches. Regarding soteriology, throughout the various debates concerning the specifics of Christ’s divinity, the earliest and most formative belief concerning Christ is that He is God and Man.
While there has never been any fully conclusive confession demonstrating how God and Man where joined in the person of Jesus, within the Christian tradition there seems to have always been a belief in Jesus as the God-Man sent into the world to save people from their sins. Therefore, the Christian belief regarding the incarnation may be summed in the following way: Jesus Christ is fully God and fully man, though we know not precisely how.
 Oxford English Dictionary. “Incarnation“. Oxford University Press, 2010. Web. 9 Feb. 2011.  Maurice Wiles. The Christian Fathers. London: SCM Press, 1977. 24.  J.N.D. Kelly. Early Christian Doctrines. Fifth ed. London: Continuum, 2009. 83-87.  Ibid., 88. See also the general perspectives of scholars such as Larry Hurtado and Richard Bauckham on this topic.  Ibid., 89.  Wiles, Fathers, 26.  Ibid., 56-57.  Ibid., 57.  Ibid., 59.  Ibid., 59-60.  Ibid., 60-63.  Ibid., 63-65.  Ibid., 65-66.  Ibid., 66.  Ibid.  Roger E. Olson. The Story of Christian Theology: Twenty Centuries of Tradition and Reform. Downers Grove, IL: InterVarsity Press, 1999. 161-235. See also Henry Chadwick (The Early Church. Revised ed. London: Penguin Books, 1993. 125-36.), Dairmaid McCulloch (A History of Christianity. London: Penguin Books, 2010. 189-222.), and J.W.C. Wand (A History of the Early Church to A.D. 500. London: Routledge, 1994. 143-178.) on this period.  Wiles, Fathers, 67-71.  Ibid., 70-71.  Ibid., 72-77.  Ibid., 72-73.  Ibid., 74.  Ibid., 76.  Ibid., 79.  Ibid., 80-81.  Maurice Wiles. The Making of Christian Doctrine. Cambridge: Cambridge University Press, 2008. 152. . Ibid., 162-164.  Ibid., 164.  Ibid., 164-166.
A version of this essay was originally written for Dr. Margaret Yee of St. Cross College, Oxford University during the Hilary 2011 term.