There are two ways to break the principle of unity: by an equal separation (dualism) or by an inequal separation, in which one term dominates and "swallows up" the other. Both of these options were evident in the early history of the church's discussions regarding the nature(s) of Christ.
Development of Christology:
1. Unity and Diversity: Given that Christ has two natures that are equally important, we affirm that the natures are united in Christ's personality. The two natures are distinct before and after union.
2. Diversity and Equality: Given that the natures of Christ are united in one Person, we affirm that the two natures are not of the same kind; the Creator/creature distinction is absolute. Christ possesses both of these natures or substances equally and truly.
3. Equality and Unity: Given that the two natures of Christ are distinct and different, we affirm that neither nature is an illusion in Christ; both are real. Christ is one Person, not two persons or souls or wills.
The Incarnation (when Christ was conceived and born through Mary) adds another complication to the question of the two natures of Christ. Some early views proposed that Christ's nature(s) were different before and after the Incarnation. However, ultimately the view prevailed that Christ's two natures were eternal, parallel, and united in one Person. Hence time does not play a role in the doctrines of the Trinity or of Christ. Theological issues dealing with temporal change are discussed further in the trilogic relations between Sovereignty, Creation and Providence. See the index for more details about these.