On the basis of primary and secondary sources of the church history, the author analyses the initiation of Christological debates in the history of Christianity. The article analyses the bases of the initiation of the Christological debates and highlights the key concepts of the doctrine of Christology. The article starts with the analysis of the concept of Logos, shows its gradual development during the history of Christianity, the basic ideas of the Church Fathers as Athanasius and Epiphanius, and shows the bases-structuresof the theology of Apollinarius. The author shows how one of the future remarkable theologians of Alexandrian school Apollinarus could not formulate as due his basic ideas, which leaded to the reprehension of the Ecumenical Church.