It is highly significant that the Incarnation of the Word made flesh is expressed relationally as the hypostatic union. The Greek word, hypostasis, expresses two fundamental relational elements:
In more modern terms, we say that the relationship is "in stasis," but this can be misleading. We need to recognize that the relationship changed, not in the mind of God, but in human history. The relationship between the divine and human sides changed when Jesus rose from the dead in a new, glorified, state. The relationship which already existed when Jesus was in the flesh was perfected in his passion, death and resurrection. This perfection, along with our relationship with Jesus, is the relational basis for our salvation.
None of this, however, captures the full meaning of that relationship. A more fundamental perspective on that relationship derives from considering the relationship of identity. The human mind and will of Jesus, which is distinct from his divine intellect and will, sees the Incarnation as a single person, the second person of the Trinity, albeit with two natures. The divine intellect and will sees the Incarnation in the same way. This sense of identity is fundamentally an identity of personhood.
This identity of personhood is established and sustained by the combined act of the intellect and will of both natures, divine and human. As such it is eternal, even though it played out in human history and continues to play out in heaven. This identity of personhood is possible because of the confluence of the divine and human intellects and wills.
Furthermore, this sense of identity is expansive. Jesus, in both his divine and human intellects and wills, freely chose to identify himself with humanity as a whole. Thus, the Mystical Body of Christ has real theological meaning and reality.
This sense of identity is particularized. Jesus, in both his divine and human intellects and wills, freely chose to be born of the Virgin Mary (the divine will having chosen from all eternity and the human will having assented after the fact), and to see himself, as a person, as the son of Mary as well as the son of God.