In this post, I will offer a critique of the traditional Christian doctrine of the hypostatic union of Christ’s person. This doctrine asserts that Christ was both truly God and truly man. The orthodox position on the relation of the two natures in Christ has historically been that Christ was not two persons but rather had two natures, a divine nature and a human nature. Because of this, I will be critiquing that concept of the hypostatic union.
The Nature of the Assertion
If this assertion is to say that Christ has, as in possesses, both a divine essence and a human essence, then this seems impossible, since God does not possess His essence but rather is His essence; for that which is possessed is necessarily different than that which possesses it. If God possesses His essence, then His essence preceded Him, which is impossible because God is by definition preceded by nothing. Hence, the divine essence cannot be possessed. For a deeper discussion on this, see my post on the absolute oneness and the absolute independence of God.
On the other hand, the human essence can be possessed in that it precedes existence whereas in God, His essence is His existence. Thus, a human being simply does not exist until the essence, which is potential, acquires its existence from another. Therefore, Christ could not have possessed the divine essence but could have possessed the human essence.
Yet, Christ is defined as both divine and human. In his humanity, then, it must be stated that Christ came into existence, since the existence of a human being is instantiated; and that which is instantiated necessarily has a cause. The Son, on the other hand, in Christian theology has always been God and, thus, would not possess existence. In other words, the Son has no cause. However, if the Son is Christ, it must be said that the Son became Christ, that is, an essentially different person than himself. Therefore, to remain logically consistent, one cannot say that Christ has always existed.
Here, a problem arises. The divine essence, more specifically God, exists necessarily, which implies that God’s existence is the same as His essence. In contrast to this, the existence of the human essence is only possible, that is, it can possibly exist or possibly not exist, since its existence is acquired. Thus, if Christ were both fully God and fully man simultaneously, then Christ’s existence would be simultaneously both necessary and contingent, but this is impossible. To say that something is necessary is to say that its nonexistence is impossible, but to say that something is contingent is to say that its nonexistence is possible. However, something cannot be both impossible and possible at the same time and in the same sense. It is a logical contradiction, then, to say an existent (one that exists) is both necessary and contingent simultaneously.
However, there is another problem. If the Son took on a different, contingent essence, then he would seem to be at the same time two separate beings, which would make one being two beings at the same, an absurdity. This is because a being may be simply defined as that which exists, whether necessarily, contingently, or impossibly. But if Christ has two different essences, then he has two different existences, or rather is one existence (the divine) and possesses the other (the human).
Yet another problem is that it seems to be incoherent with the logic used for the doctrine of the Trinity. The Trinity makes God to be one being in that He is one essence. If the unity of a being is determined by the number of its essences, which it must be for the classical understanding of the Trinity to be true, then to have two different essences is to be two different beings. Again, this is metaphysically absurd.
If Anyone Should Comment That Christ Has Two Natures
The traditional wording of the hypostatic union is that Christ is one person with two natures, a divine nature and a human nature. Throughout this post, I have used the term essence rather than nature. However, this does not mean that I have misunderstood the Trinity or that I have set up a straw man argument. By saying that Christ has a divine nature and a human nature, Trinitarian theologians mean that Christ is fully God and fully man at the same time. It is impossible to be fully man without having a human essence, and it is nonsensical to state the contrary. Furthermore, the statement that Christ has a human nature implies that Christ has a human essence. Similarly, to state that Christ has a divine nature implies that Christ has (or is) the divine essence.
I conclude with this: the doctrine of the hypostatic union of Christ is logically contradictory and impossible. Christ, then, could not have been both fully God and fully man. As far as I am aware, holding to the doctrine of the hypostatic union is similar to holding to the doctrine of the Trinity. If one wishes to believe in these, that person must either deny plain logic, redefine terms until the doctrines are incoherent, or admit that it is illogical but necessary to their faith.