But since no relation can be affirmed of one subject alone, inasmuch as a predicate wanting relation is a predicate of substance, the manifoldness of the category of relation, Trinity is secured through the category of relation, and the Unity is maintained through the fact that there is no difference of substance, or operation, or generally of any substantial predicate. So then, the divine substance preserves the Unity, the divine relations bring about the Trinity. Hence only terms belonging to relation may be applied singly to Each. For the Father is not the same as the Son, nor is either of Them the same as the Holy Spirit. Yet Father, Son, and Holy Spirit are each the same God, the same in justice, in goodness, in greatness, and in everything that can he predicated of substance. One must not forget that predicates of relativity do not always involve relation to something other than the subject, as slave involves master, where the two terms are different. For equals are equal, like are like, identicals are identical, each with other, and the relation of Father to Son, and of both to Holy Spirit is a relation of identicals. A relation of this kind is not to be found in created things, but that is because of the difference which we know attaches to transient objects. We must not in speaking of God let imagination lead us astray; we must let the Faculty of pure Knowledge lift us up and teach us to know all things as far as they may be known.
I have now finished the investigation which I proposed. The exactness of my reasoning awaits the standard of your judgment; your authority will pronounce whether I have seen a straight path to the goal. If, God helping me, I have furnished some support in argument to an article which stands by itself on the firm foundation of Faith, I shall render joyous praise for the finished work to Him from whom the invitation comes. But if human nature has failed to reach beyond its limits, whatever is lost through my infirmity must be made good by my intention.