When we say that the Second Person holds two natures, viz. one divine and one human, we are making a distinction between the person and his nature. Again, when we say that the 3-divine persons hold one undivided nature, we are making the same distinction. So the question is, what distinguishes the person from his nature, or, what is there in the “person” that is not there in the “nature” and vice versa?
Now let me offer a purely philosophical explanation. The following is from the thread " The Three, " on this page and is post #66 by Imelahn and I think it is excellent.
" Well, I have an answer, but it involves some subtle metaphysics. (My source for this is Summa Theologiae Ia q. 28.)
Just for review, Aristotle observed that the realities we observe and deal with each day are what he calls substances: beings with an independent existence, like trees, fish, stones, and men. These substances have various characteristics—their color, size, shape, and so on—which he calls accidents. (I assume that most of my readers know that, but just so we are clear: for Aristotle, the accidents are, so to speak, only second-class citizens. There is no such thing as “redness” in the abstract, only red apples, and red roses, and so on. They don’t exactly “exist,” tout court, but only “exist in something else.”)
I think Aristotle’s analysis of reality (assumed by Thomas Aquinas)—which resolves beings into “substance” and “accident” like that—is fundamentally sound, and can be useful for answering this question.
The distinction between substance and accident (I think it is clear that the apple is not the same as its redness) is evidence of a metaphysical composition: even the most seemingly simple realities turn out to have a kind of internal “division.” Substance-and-accident is the easiest one for us to grasp, but there are others (notably matter-and-form, essence-and-being), which it is not necessary to get into here.
What concerns us here is a particular “genus” of accident that Aristotle calls the “pros ti,” the “towards which.” Substances are frequently observed to have a certain reference to another substance: for example, the earth to the moon, a father to a son, and even (although they are not technically substances) the right hand to the left hand. We usually call that reference “relation.”
“Relation” is an interesting category. For all other genera of accidents, we understand what they are by comparing them to the substance in which they inhere. (Color, for example, is a quality of a substance; size is a property of a substance, and so on.) Relation, however, is different, because we understand what it is by comparing one thing to something else. (We compare a father to his son, and vice versa; the moon with the earth; and so on.) The very notion of relation contains comparison with something else.
Therefore, in a creature, relation can be considered in two ways: inasmuch as it is a characteristic that “inheres” in a substance, or else according to its notion, which entails a comparison with something else.
When we talk about God, however, we must always keep in mind that He is very different from His creatures, while at the same time being the source of all perfections in those creatures. Hence, when we see a perfection in a creature, we must recognize God as its source. He must, therefore, also possess that perfection, but in a much more eminent way than in His creatures. (We are assuming that the perfection in question is not intrinsically tied to some kind of potential principle; for example, size is tied to matter, and so it cannot be attributed to God.)
Take goodness, for example. Many beings are good to different degrees, especially some human beings we know. That goodness must come from God as its source; therefore God must be good. But God isn’t just “good,” not “good” in the human or creaturely sense; if He is the source of all goodness, it would be better to say that He is Goodness Itself.
One of these perfections is unity. As has been mentioned already in this thread, God must be utterly simple, because there is nothing prior to Him with which He could be “composed.” So all those kinds of composition I mentioned—essence-and-being, matter-and-form, substance-and-accident—are to be excluded entirely from God.
Now, the ability to make relations is indeed a perfection that could be attributed to God. Such a relation could not, however, be an “accident” that inheres in God, because that would imply a composition in God. Just as in God, the Essence is the same as His Being, his Relations are the same as his Substance. In God, the very relations are subsistent.
But, as we saw, the very notion of relation entails a comparison with something else. Now, God cannot (properly speaking) have a “relation” with one of HIs creatures (because that would imply that one of His creatures is “prior” to Him in some way). But there is nothing stopping one (subsistent) Relation from being related to another (subsistent) Relation. And inasmuch as they are relative to each other, they are really distinct.
In summary: the Divine Persons are actually identical to the Relations themselves. Since relations in God can’t be accidents, but have to be identical to His very Substance, it is therefore possible for the Persons to be related to each other (hence really distinct), but still be identical to the Divine Essence. "
God Bless
Linus2nd
