FIFTH ARTICLE: WHETHER THE SON IS IN THE FATHER AND THE FATHER IS IN THE SON

This article deals with circumincession, which is the mutual coexistence of the divine persons in each other so that the Father is in the Son, the Son in the Father, and both in the Holy Ghost, and the Holy Ghost in both.

The difficulty arises because what goes out of another is not in the other. But the Son goes out of the Father from all eternity. Moreover, one of two opposites is not in the other opposite.

Reply. The affirmative reply is of faith according to the Scriptures, for Christ said: "Do you not believe that I am in the Father, and the Father in Me?"[588] Such was the interpretation of the Fathers, especially St. Augustine.[589]

The theological argument is in three parts: the Son is in the Father, and the Father is in the Son:

1. according to essence, which is numerically the same in the persons;

2. according to the relations, because they mutually involve each other, although they are opposites;

3. according to the procession, because it is immanent or ad intra and not ad extra.

Circumincession signifies consubstantiality, the immanence of the processions, and the reciprocity of opposite relations. An analogy can be seen in the equilateral triangle, where each angle is in the other two.

Objection. One of two opposites is not in the other opposite, because the opposites are really distinct. Therefore the Father is not in the Son.

Reply. I distinguish the antecedent: one of the opposites formally as an opposite is not in the other opposite, I concede; nevertheless by reason of the same essence the relations have the same "esse in" and according to the "esse ad" they mutually refer to each other and are inseparable, although really distinct. Thus, by circumincession the Father and the Holy Ghost are with the incarnate Son in the Holy Eucharist.[590]