Chapter II.
What must be held concerning the trinity of persons and the unity of essence.
First, therefore, concerning the Trinity of God, three things must be considered: namely, how the unity of substance and nature stands together with the plurality of persons; second, how it stands with the plurality of apparitions; third, how it stands with the plurality of appropriations.
Concerning the plurality of persons in the unity of nature, right faith dictates that this must be held: namely, that in the unity of nature there are three persons, Father and Son and Holy Spirit, of whom the first is from none, the second is from the first alone through generation, the third is from the first and second through spiration or procession:
so that the trinity of persons does not exclude from the divine essence the highest unity, simplicity, immensity, eternity, immutability, necessity, and also primacy; but rather includes the highest fecundity, charity, liberality, equality, kinship, conformity, and inseparability: all of which sound faith understands to be in the most blessed Trinity.
Now the reason for this truth is this: because faith, since it is the principle of the worship of God and the foundation of that doctrine which is according to piety, dictates that one must think of God most highly and most devoutly. But one would not think most highly if one did not believe that God could communicate Himself in the highest degree; one would not think most devoutly if one believed that He could but would not; and therefore, in order to think most highly and most devoutly, faith declares that God communicates Himself in the highest degree, by eternally having a beloved and a co-beloved, and through this, that God is one and three.
Now to this faith, insofar as it dictates that one must think most devoutly of God, the whole of sacred Scripture bears witness, which is called the doctrine according to piety: because it confesses that God has offspring, whom He loves in the highest degree, a Word coequal to Himself, which "He begot from eternity, in whom He disposed all things"; through which He produced and governs all things; through which also, made flesh, out of the highest kindness He redeemed man by His most precious blood and nourished the redeemed; through which also at the end of the world, bestowing the highest mercy, He will free from all misery, so that through Christ all the elect may be sons of the most high Father, in whom will be the consummation of all piety, both of God toward us, and conversely.
Insofar as faith dictates that we must think most highly concerning God, not only does sacred Scripture bear witness to this, but also every creature, according to what Augustine says in the fifteenth book On the Trinity, chapter four: "For not only does the authority of the divine books proclaim that God exists, but the whole universal nature of things itself, which surrounds us and to which we also belong, proclaims that it has a most excellent Creator, who gave us a natural mind and reason, by which we judge living things preferable to non-living things, things endowed with sense to things without sense, intelligent things to non-intelligent things, immortal things to mortal things, powerful things to powerless things, just things to unjust things, beautiful things to deformed things, good things to evil things, incorruptible things to corruptible things, immutable things to mutable things, invisible things to visible things, incorporeal things to corporeal things, and blessed things to miserable things. And through this, since we without doubt set the Creator above created things, it is necessary that we confess him both to live supremely and to perceive and understand all things, and to be unable to die or be corrupted or changed, and not to be a body, but a spirit most omnipotent, most just, most beautiful, most good, and most blessed." - Behold, in these twelve are included the most exalted perfections of the divine being. But afterwards, as he himself shows, these twelve are reduced to three, namely eternity, wisdom and beatitude: and these three to one, namely to wisdom, in which are included the begetting mind, the Word as offspring, and love binding both together, in which faith dictates the most blessed Trinity to consist. And since the highest wisdom posits the Trinity, it no less posits all the most noble conditions previously established, namely unity, simplicity, and the other consequent ones: it is necessary that all the aforementioned perfections of the divine being stand together with the most blessed Trinity.
Ch. III.
On the sound understanding of this faith.
For the sound understanding of this faith, sacred doctrine teaches that in the divine there are two emanations, three hypostases, four relations, five notions, and from these only three personal properties.
Now the reason for understanding the aforesaid is this: since the first and highest principle, by the very fact that it is first, is most simple, and by the very fact that it is highest, is most perfect, it therefore communicates itself most perfectly, because it is most perfect, and preserves complete indivision, by the very fact that it is most simple. And therefore, with the unity of nature preserved, there are therein perfect modes of emanating. Now the perfect modes of emanating are only two, namely by way of nature and of will. The first is generation, the second is spiration or procession, and therefore these are therein.
And because by two substantial emanations two hypostases must necessarily emanate, it is also necessary to posit that the hypostasis that first produces does not emanate from another, lest there be an infinite regress: therefore there are therein three hypostases.
And because to each emanation there corresponds a twofold relative relation, therefore there are therein four relations, namely paternity, filiation, spiration, and procession.
Now through these relations the divine hypostases become known to us; and besides this, that hypostasis also in which there is the first principle of originating becomes known because it is not produced — for this is a mark of nobility in it — therefore there are five notions, namely the four aforesaid relations together with innascibility.
And because each of the persons has one property through which it is principally known, therefore there are only three personal properties, which are expressed properly and principally by these names, namely Father and Son and Holy Spirit.
For since it is proper to the Father to be innascible or unbegotten, to be a principle not from a principle, and to be the Father: innascibility makes him known by way of negation, although consequently by way of position, because innascibility in the Father posits a fontal fullness; principle not from a principle, by way of position with negation; to be the Father, by way of position and relation, properly, completely, and determinately.
Similarly, since the Son is image, word, and son: image names that person as an expressed likeness; word, as an expressive likeness; son, as a hypostatic likeness. Again, image names him as a conformed likeness; word, as an intellectual likeness; son, as a connatural likeness.
In this manner, since it is proper to the Holy Spirit to be a gift, to be the bond or charity of both, and also to be the Holy Spirit: gift names him as given voluntarily: charity or bond, as given voluntarily and preeminently; Holy Spirit, as given voluntarily, preeminently and hypostatically .
Hence it is that through these three names, which are Father and Son and Holy Spirit, the personal properties of the three persons are intimated.
These things, therefore, must be held for a sound understanding of faith in the Trinity.