We have seen that Cyril's careful distinction between ἴδιος and οἰκειότης plays an important role in his portrayal of grace in his early writings. During and after the Nestorian controversy, however, Cyril virtually ceases using the word οἰκειότης. 1 One can account for this striking change by noting that his attention has shifted from more general soteriological concerns to the specific question of technical christology: the relation between Jesus' deity and humanity. In spite of this paucity of direct reference to divine οἰκειότης, Cyril's technical christology grows directly out of his conviction that God shares with humanity the intimate communion he has within himself. As a result, the christological notes that Cyril sounds so emphatically during the controversy are in complete harmony with the soteriological symphony he has conducted previously, and his theology of grace is a large part of what drives his expression of Christ's unified person.
In this chapter, I will examine the consistency of Cyril's broader early thought with his more narrowly christological thought in his later writings. I will do this by explaining his conviction that the word οἰκειότης is inadequate to describe the christological union, by probing the relation between grace and his insistence on the unity of Christ's person, by looking at the way Cyril uses the word ἴδιος to express that personal unity, and by considering the relation between Cyril's understanding of grace and two of his most famous slogans: the appellation Theotokos for Mary and the formula 'one incarnate nature of God the Logos' ().