The holiday of Christmas cannot be properly understood or recognized without an understanding of what is true to its central mystery: the Incarnation. This Christian doctrine is important to Christianity because without the knowledge of who Jesus Christ is and why we need Jesus Christ, there cannot be a complete understanding of the gospel or the means of salvation. The first gospel shows the importance of knowing who Jesus Christ is. Based on a simple question that Jesus asks his disciples, in Matthew 16:13: "Who, say men, I am the Son of God", a Christian from a non-Christian and a heretic from a non-heretic can be distinguished. The attempt to answer the fundamental question: “Who is Jesus Christ?” » and further: “Why do we need Jesus Christ? is important because it broadens and enriches our understanding of Jesus Christ and also directs our hearts to why we celebrate his birth during the Christmas season. Many writings attempt to help us understand who and why we need Jesus Christ. One book in particular may be among the most profound of all. CS Lewis writes in the preface to the book written by Athanasius, the great 4th century bishop of Alexandria, that it is indeed a “masterpiece” and “an image of the Tree of Life.” Athanasius proposes an approach to the doctrine of the Incarnation, which attempts to defend the Christian faith in his treatise "The Incarnation of the Word of God". In this work he seeks to refute the heresy of this and future periods and to explain why Jesus is the Christ. His approach to this doctrine provides a useful scriptural basis for the importance of the incarnation. This... middle of paper ...... I have a mother; no woman can give birth to God. Cyril of Alexandria suggested that Nestorius proposed that Jesus had two natures united in a purely moral union. After Nestorianism came Eutychianism. Eutyches, who was summoned several times to the permanent synod of Constantinople in 448, finally appeared and stated his position that Christ had two natures before the incarnation, who had only one after. The result of the Synod was that Eutyches was deposed and excommunicated, and the doctrine of the one nature rejected. Works Cited Erickson, Millard J.. The word has become flesh. Grand Rapids, Michigan: Baker Book House, 1991. Fitzwater, P.B. Why God became man. Chicago: The Bible Colportage Ass'n., 1934. Gore, Charles. The incarnation of the Son of God. London: J. Murray, 1891.Streatfeild, George Sidney. The incarnation. London: Longmans, Green, 1910.