Aquinas on the Metaphysics of the Hypostatic Union

by Michael Gorman

“the human nature becomes an individual subsisting thing, only insofar as it is united to the divine person…. the concrete term ‘man’ is only to be applied to Christ’s human nature insofar as that nature is being considered in relation to its union with the Divine supposit

Third, not because anything at all is lacking to it, but rather because something is added to it – namely, a union with the Word.

Aquinas is not lack of a mode or lack of an act of existence, but the addition of a relation to the Word:

Imagine that what is assumed is a human person. It cannot survive being assumed, lest there be two persons in Christ,

place. As he puts it, “[S]omething – namely a person – would be destroyed on the assumption of a pre-existent nature. So being a person involves something positive over and above a nature.”

This would be analogous to the way in which the addition of marital union causes a bachelor to become a non-bachelor.

person, which is contrary to the faith. But if that hypostasis or person (the one in which the nature to be assumed by the Word pre-existed) did not remain, that could not happen without its being corrupted: for no singular being can cease to be what it is except through corruption.

it would have been necessary for that human being who had existed before the union to be corrupted.

consequently the human nature existing in it [would hav...

If the Word assumed a pre-existing person into a true union in person, then that person would go out of existence, and when it went out of existence, its nature would go out of existence along with it.

In other words, a person would not have been converted to a mere nature – it would have been destroyed in such a way that nothing was left behind at all.

Overall, I think that these two passages lend little support to the idea that, for Aquinas, a person involves something positive over and above a nature.

Overall, it seems best to say that for Aquinas, the fact that there is no second person in Christ is explained by the positive fact of union, and not by the lack of a mode or the lack of a proper act of existence.

Aquinas thinks the union in person blocks these other things.

on Aquinas’s understanding, posterior to the positive fact that the human reality is united in person to the Word.

(1) On Aquinas’s way of thinking,44 the reason why the human nature does not ground a supposit is that it is joined in person to the Word.

Third, I have discussed the old problem of why, for Aquinas, there is no second person in the hypostatic union. Is it because something is lacking to the human nature that other human natures have, or is it because something is added to it? I have made common cause with those who hold to the latter interpretation, although I have added my own distinctions.

Aquinas says that there are exactly two places where this correlation breaks down: the incarnation and the Trinity.

See SCG IV, c. 43; ST III, q. 4, a. 2. At this

questions that arise when he considers the two natures as united in one person.

according to the real sense, only items that show up in one of Aristotle’s ten categories are counted as existing.

essences

(Substances and accidents both belong directly to Aristotelian categories; essences, whether substantial or accidental, do

therefore the human nature is joined to the Son of God hypostatically or personally…and not accidentally,

To sum up, then, in all five of the texts in which he deals with the existences of Christ as his main concern, Aquinas focuses on existence of supposit.

Substances exist. Socrates, say, has an actual foothold in the actual world. It is a fact that he is a denizen of reality. This fact, the fact that he exists, is his existence as fact. But that is not the most basic thing that can be said. Socrates exists, he has factual existence, but this is so in virtue of certain principles that belong to him.

A second-order remark might be helpful at this point. Just as it is hard to understand what an essence

is tempting, for example, to think of essences as dehydrated beings, with esse as act playing the role of water:

God pours water onto the essences, and they swell up into full-blown actual beings, like the little sp...

what is relevant here is simply that essence and existence are not little things that get cobbled together to make a big thing. Such f...

Well, any Thomist will want to emphasize, first, that being in one way, rather than another, is different from being at all, rather than not being. That, put rather crudely, is the difference between essence and existence. If the difference between them is really rooted in reality, and not just in the mind, then it is at least plausible to posit really distinct principles to account for them: not only an essence-principle, but also an existence-principle.

First, a form or nature can for Aquinas be a principle by virtue of which a supposit subsists. In virtue of having such a form or nature, the supposit exists as a supposit.

Consider the cat Rusty. Without his felinity, Rusty would not be a supposit, indeed he would not exist at all – his felinity constitutes him as possessing unqualified

In these texts, Aquinas says that Christ can have only one existence, and it is clear that what he means by existence is the (factual) existence of a supposit.

is clear that he means the simple existence of a supposit, its unqualified existence, its subsistence. Christ cannot have a divine subsistence and also a human subsistence, because then he would be two subsisting beings, which is (or amounts to) Nestorianism.

inasmuch as they do not rule out Christ’s having a second qualified existence.

Christ’s humanity is here said to be a principle of qualified existence for him, a principle of qualified existence of a supposit.

I have said that in these category III texts, Aquinas holds that Christ has no existence from his humanity, but a more precise formulation might put it this way: Christ has, from his humanity, no existence in the essential or substantial order.

Aquinas feels forced into this position by the combination of two things: the idea that Christ’s humanity is not an accident, and the idea that qualified existence is always accidental existence.

The result is paradoxical. Aquinas’s desire to deny that Christ’s humanity is an accident goes with his desire to treat that humanity with full ontological seriousness;

asking whether Aquinas’s understanding of how the two natures exist together can be maintained without contradiction;

It seems Aquinas needs to predicate both “changeable” and “unchangeable” of Christ; this might not be a contradiction, but it certainly sounds like one.

Aquinas’s understanding of Christ’s knowledge and power. Aquinas thinks that Christ, in virtue of his divine nature, knows everything that can be known and is able to do everything that can be done.

Christ has, in virtue of his human nature, a mode of knowing that does not allow him to know everything that can be known, and he has a mode of acting that does not allow him to do everything that can be done.

in having tw...

strategy like the one just described can be called “reduplicative,” because it uses reduplicative phrases such as “insofar as he is divine” or “qua divine.”

“replacement strategy,” because it seeks to substitute reduplicative statements for non-reduplicative statements:

His remarks are so brief and undeveloped that a certain kind of agnosticism is in order.

“reduplicative” phrases like “qua human” or “insofar as he is human.”

“mereological,”