Nicene and Post-Nicene Fathers, Vol. II:
City of God: Chapter 24

Chapter 24.—Of the Divine Trinity, and the Indications of Its Presence Scattered Everywhere Among Its Works.

We believe, we maintain, we faithfully preach, that the Father begat the Word, that is, Wisdom, by which all things were made, the only-begotten Son, one as the Father is one, eternal as the Father is eternal, and, equally with the Father, supremely good; and that the Holy Spirit is the Spirit alike of Father and of Son, and is Himself consubstantial and co-eternal with both; and that this whole is a Trinity by reason of the individuality 497 of the persons, and one God by reason of the indivisible divine substance, as also one Almighty by reason of the indivisible omnipotence; yet so that, when we inquire regarding each singly, it is said that each is God and Almighty; and, when we speak of all together, it is said that there are not three Gods, nor three Almighties, but one God Almighty; so great is the indivisible unity of these Three, which requires that it be so stated.  But, whether the Holy Spirit of the Father, and of the Son, who are both good, can be with propriety called the goodness of both, because He is common to both, I do not presume to determine hastily.  Nevertheless, I would have less hesitation in saying p. 219 that He is the holiness of both, not as if He were a divine attribute merely, but Himself also the divine substance, and the third person in the Trinity.  I am the rather emboldened to make this statement, because, though the Father is a spirit, and the Son a spirit, and the Father holy, and the Son holy, yet the third person is distinctively called the Holy Spirit, as if He were the substantial holiness consubstantial with the other two.  But if the divine goodness is nothing else than the divine holiness, then certainly it is a reasonable studiousness, and not presumptuous intrusion, to inquire whether the same Trinity be not hinted at in an enigmatical mode of speech, by which our inquiry is stimulated, when it is written who made each creature, and by what means, and why.  For it is the Father of the Word who said, Let there be.  And that which was made when He spoke was certainly made by means of the Word.  And by the words, “God saw that it was good,” it is sufficiently intimated that God made what was made not from any necessity, nor for the sake of supplying any want, but solely from His own goodness, i.e., because it was good.  And this is stated after the creation had taken place, that there might be no doubt that the thing made satisfied the goodness on account of which it was made.  And if we are right in understanding; that this goodness is the Holy Spirit, then the whole Trinity is revealed to us in the creation.  In this, too, is the origin, the enlightenment, the blessedness of the holy city which is above among the holy angels.  For if we inquire whence it is, God created it; or whence its wisdom, God illumined it; or whence its blessedness, God is its bliss.  It has its form by subsisting in Him; its enlightenment by contemplating Him; its joy by abiding in Him.  It is; it sees; it loves.  In God’s eternity is its life; in God’s truth its light; in God’s goodness its joy.

Footnotes

Proprietas.  [The Greeks call it ἰδιώτης or ἴδιον, i.e. the propriety or characteristic individuality of each divine person, namely the fatherhood, paternitas, ἀγεννησια, of the first person; the sonship, filiatio, generatio, γεννησία, of the second person; the procession, processio, ἐκπόρευσις, of the third person.—P.S.]