Let me start by saying that the term hypostasis is simply the Greek technical term for subsistence or person, and so, the doctrine of the Hypostatic Union concerns the union of the two natures (divine and human) in the one Divine Person of the eternal Son of God. In the incarnation God the Word assumed a full and complete human nature, but did not become a human person; instead, the Divine Hypostasis of the Word took the place of the connatural human hypostasis that normally actuates and concretizes a particular human nature as this or that particular man. Therefore, after the incarnation, Christ is one Divine Person in two natures, divine and human. Connected to the doctrine of the Hypostatic Union is the doctrine of the communicatio idiomatum (i.e., the communication of properties), and this doctrine allows one to predicate things or actions flowing from either nature (divine or human) to the one Divine Person of Christ. As a consequence of the doctrine of the communicatio idiomatum, it is true to say that Mary is the Mother of God (i.e., the Theotokos), not because she gives birth to the Divine Nature itself, but because she gives birth to the Divine Person of the Word Incarnate.

Finally, as far as explaining the doctrine of the incarnation to Muslims concerned, it is important to note that they have their own doctrine of the inlibration of the word of God. Islamic theology teaches that the Qur'an itself has two natures, an earthly nature (i.e., the paper, ink, etc.) and a heavenly nature (i.e., the inspired words themselves). Moreover, the Qur'an is held to be eternal and uncreated, and so it is Allah's word from all eternity, distinct from Allah, but not separate from him. In other words, Muslims believe in two eternal and uncreated things or entities, Allah and the Qur'an.

I hope this helps, and if you have more questions, don't hesitate to ask.

Christ is a Divine Person who has assumed a human nature, and in doing that He became man. Thus, Christ is one Divine Person and one Divine Being, who in the incarnation assumes a complete human nature (body and soul), and in the process He becomes man. But He is not thereby a human person or a human being, because to say that would be to fall into the Nestorian heresy. There can only be one subject of predication and one subject of action in Christ, and that one subject is the Divine Person of the Word, who acts in and through both natures. Moreover, because the union does not occur within the natures themselves, there is no blending of the two natures, and so they remain distinct, but are united in the one Divine Person of the Word; and in addition, because the union is hypostatic it follows that the two natures are now inseparably united and subsist in the eternal Person of the Son of God.

Let me, in a rather simplified manner, chart out the orthodox Catholic teaching in opposition to the two major Christological heresies of the 5th century:

The Orthodox Catholic Dogma as Formulated at the Councils of Ephesus and Chalcedon

1. Christ is one Divine Person in two natures, divine and human.

The Nestorian heresy

2. Christ is a Divine Person and a human person, with a divine nature and a human nature.

Nota Bene:  The problem with the Nestorian position is that it is ultimately a denial of the reality of the incarnation, for this reduces the incarnation to an indwelling of man by God, and thus it is not a true incarnation properly speaking. It involves the assumption, or worse, the possession, of one person by another person, which is not really possible.

The Monophysite heresy

3. Christ is one Divine Person with one nature after the incarnation.

Nota bene:  The problem with the Monophysite position is that it is a denial of the incarnation, because the human nature assumed is either destroyed or absorbed by the divine nature and no real incarnation has occurred. One other possible problem is that the "one nature" mentioned, could be thought of as a blending of humanity and divinity, and this leads to other theological problems, because the divine nature is immutable and cannot change.

The Hypostatic Union will never cease, and so the death of Christ did not separate the Divine Person of the Word from His body and soul, even though His body and soul were themselves separated in death. As Dr. Ott explains in his book on Catholic doctrine, Christ's ". . . death did not dissolve the attachment of Godhead and humanity, or of their parts. Even after their separation the body and the soul remained hypostatically united with the Divine Logos." [Dr. Ludwig Ott, Fundamentals of Catholic Dogma, page 151]

The Hypostatic Union

by Steven Todd Kaster

Original Version:  25 August 2004 (from a thread at the Phatmass Phorum)

This essay is based on posts taken from the forum thread linked above, but was slightly edited into its present form for the sake of clarity on:  23 January 2026

Copyright © 2004, 2026 - Steven Todd Kaster