Chapter 50 — That a Trinity of persons in God is not opposed to unity of essence

From all that has been said we must gather that we hold there to be a kind of three in the Godhead, which nevertheless is not opposed to the unity and simplicity of the divine essence. For we must acknowledge that God exists both in his nature and as known and loved by himself.

But this occurs otherwise in God than in us. For man is a substance in his nature, but his actions of knowing and loving are not his substance. Considered in his nature, man is indeed a subsisting thing; as he exists in his mind, however, he is not a subsisting thing, but a certain representation of a subsisting thing; and similarly with regard to his existence in himself as beloved in lover. Therefore, even though a kind of three can be considered in man—that is, man existing in his nature, man existing in his intellect, and man existing in his love—yet these three are not one, for man’s knowing is not his existence, and the same is true of his loving. Only one of these three is a subsisting thing: namely, man existing in his nature.

In God, on the contrary, to be, to know, and to love are the same thing. Therefore, God existing in his natural being and God existing in the divine intellect and God existing in the divine love are one thing. Yet each of them is subsistent. And, because Latins are accustomed to call things subsisting in intellectual nature persons, while Greeks call them hypostases, consequently the Latins say that there are three persons in God, and the Greeks say that there are three hypostases, namely, the Father, the Son, and the Holy Spirit.