Q: Whether Relation Is the Same As Person?

A: On the contrary,
in God "what is" and "whereby it is" are the same, according to Boethius (De Hebdom.). But the Father is Father by paternity. In the same way, the other properties are the same as the persons.

I answer that,
Different opinions have been held on this point. Some have said that the properties are not the persons, nor in the persons; and these have thought thus owing to the mode of signification of the relations, which do not indeed signify existence "in" something, but rather existence "towards" something. Whence, they styled the relations "assistant," as above explained (Q. 28, A. 2). But since relation, considered as really existing in God, is the divine essence Itself, and the essence is the same as person, as appears from what was said above (Q. 39, A. 1), relation must necessarily be the same as person.

Others, therefore, considering this identity, said that the properties were indeed the persons; but not "in" the persons; for, they said, there are no properties in God except in our way of speaking, as stated above (Q. 32, A. 2). We must, however, say that there are properties in God; as we have shown (Q. 32, A. 2). These are designated by abstract terms, being forms, as it were, of the persons. So, since the nature of a form requires it to be "in" that of which it is the form, we must say that the properties are in the persons, and yet that they are the persons; as we say that the essence is in God, and yet is God.

Reply Obj. 1: Person and property are really the same, but differ in concept. Consequently, it does not follow that if one is multiplied, the other must also be multiplied. We must, however, consider that in God, by reason of the divine simplicity, a twofold real identity exists as regards what in creatures are distinct. For, since the divine simplicity excludes the composition of matter and form, it follows that in God the abstract is the same as the concrete, as "Godhead" and "God." And as the divine simplicity excludes the composition of subject and accident, it follows that whatever is attributed to God, is His essence Itself; and so, wisdom and power are the same in God, because they are both in the divine essence. According to this twofold identity, property in God is the same as person. For personal properties are the same as the persons because the abstract and the concrete are the same in God; since they are the subsisting persons themselves, as paternity is the Father Himself, and filiation is the Son, and procession is the Holy Ghost. But the non-personal properties are the same as the persons according to the other reason of identity, whereby whatever is attributed to God is His own essence. Thus, common spiration is the same as the person of the Father, and the person of the Son; not that it is one self-subsisting person; but that as there is one essence in the two persons, so also there is one property in the two persons, as above explained (Q. 30, A. 2).

Reply Obj. 2: The properties are said to be in the essence, only by mode of identity; but in the persons they exist by mode of identity, not merely in reality, but also in the mode of signification; as the form exists in its subject. Thus the properties determine and distinguish the persons, but not the essence.

Reply Obj. 3: Notional participles and verbs signify the notional acts: and acts belong to a
suppositum.
Now, properties are not designated as supposita, but as forms of supposita. And so their mode of signification is against notional participles and verbs being predicated of the properties.