While perhaps not as recognized as the theological terms of the Trinity and Incarnation, the dogma of the Hypostatic Union is equally as important to understand who is the person of Jesus Christ.  This dogma professes the revealed truth that in Christ, one person subsists in two natures, the Divine and the human.  The Catechism expresses it this way:

The unique and altogether singular event of the Incarnation of the Son of God does not mean that Jesus Christ is part God and part man, nor does it imply that he is the result of a confused mixture of the divine and the human.  He became truly man while remaining truly God.  Jesus Christ is true God and true man.  (CCC464).

One simple “test” of this truth can be revealed in these four questions.  Does Jesus have a divine nature?  Does Jesus have a human nature?  Is Jesus a divine person?  Is Jesus a human person?

Usually if asked in a group, there are a chorus of “yeses” to all of the above.  But while the answer to the first three questions are yes, the answer to the fourth question – Is Jesus a human person – is “no.”  Does he have a human nature?  Yes he does.  But Jesus Christ, the second person of the Trinity is a divine person who has existed from all eternity.  The Incarnation, when he assumes a human nature, does not change who he is – a divine person who has existed from all eternity.  As Scripture tells us, “Jesus Christ is the same yesterday and today and for ever.”  (Hebrews 13:8).  Christ does not give up his divinity in the incarnation.  This is why the catechism repeatedly references Christ as one divine person who assumes a human nature.

For some, this can be seen as splitting theological hairs and not being that important in the big scheme of things.  But as with most dogmas, it was the result of a series of heresies that began to creep their way into the teaching of the early Church.  These needed to be addressed and uprooted in order to profess the truth of who Christ really is.  We already looked at the heresy of Arianism that taught that the pre-existent Christ was the first and greatest of God’s creatures but not God, and denied his fully divine status.  But there were many others.

Docestism/Gnosticism taught that Jesus Christ was a purely divine being who only had the “appearance” of being human.  Regarding his suffering, some versions taught that Jesus’ divinity abandoned or left him upon the cross while others claimed that he only appeared to suffer (much like he only appeared to be human).  Adoptionism taught that Jesus was born totally human and only later was “adopted” by God in a special or divine way, either at his baptism or his resurrection.

Nestorianism regarded Christ as a human person joined to the divine person of God’s Son sometime after his birth.  (The erroneous idea that Christ was “two persons” joined together is why the answer is “no” to the question “is Jesus a human person”).  This was a particularly divisive time in Church history.  Nestorius was the patriarch of Constantinople, a position of great prominence in the early Church.  A controversy between two factions erupted over the long known title of Mary as the Theotokos (“the one who gives birth to God”), translated in Latin as “mater Dei” which translates to English as “mother of God.”  Nestorius proposed a compromise in which the title of Mary would become the Christotokos, “the one who gave birth to Christ.”  This satisfied neither faction, and the council of Ephesus in 431 affirmed that Mary truly gave birth to the second person of the Trinity – God, and therefore the title “mother of God” for Mary is most appropriate.  The words of the council regarding what the title does and does not mean are most important — “Mother of God, not that the nature of the Word or his divinity received the beginning of its existence from the holy Virgin, but that, since the holy body, animated by a rational soul, which the Word of God united to himself according to the hypostasis, was born from her, the Word is said to be born according to the flesh.”  The council of Ephesus is the third ecumenical council of the Church.

Monophysitism taught that the human nature had ceased to exist in Christ when the divine person of God’s son “absorbed” it.  This heresy was addressed in 451 by Chalcedon, the fourth ecumenical council of the Church.  From that council, “We confess that one and the same Christ, Lord, and only-begotten Son, is to be acknowledged in two natures without confusion, change, division or separation.  The distinction between the natures was never abolished by their union, but rather the character proper to each of the two natures was preserved as they came together in one person.”  This council resulted in one of the earliest schisms in the Church when the Oriental Orthodox (also known as the Coptics) rejected the proclamation of the Council and broke communion with the Catholic Church.  The Coptic Christians can still be found today, primarily in Egypt.

One divine person, two natures – human and divine.  Jesus Christ, true God and true man.