Chapter 9.--The Three Persons Not Properly So Called [in a Human Sense].
But because with us the usage has already obtained, that by essence we understand the same thing which is understood by substance; we do not dare to say one essence, three substances, but one essence or substance and three persons: as many writers in Latin, who treat of these things, and are of authority, have said, in that they could not find any other more suitable way by which to enunciate in words that which they understood without words. For, in truth, as the Father is not the Son, and the Son is not the Father, and that Holy Spirit who is also called the gift of God is neither the Father nor the Son, certainly they are three. And so it is said plurally, "I and my Father are one." [582] For He has not said, "is one," as the Sabellians say; but, "are one." Yet, when the question is asked, What three? human language labors altogether under great poverty of speech. The answer, however, is given, three "persons," not that it might be [completely] spoken, but that it might not be left [wholly] unspoken.
[582] John x. 30
Chapter 10.--Those Things Which Belong Absolutely to God as an Essence, are Spoken of the Trinity in the Singular, Not in the Plural.
11. As, therefore, we do not say three essences, so we do not say three greatnesses, or three who are great. For in things which are great by partaking of greatness, to which it is one thing to be, and another to be great, as a great house, and a great mountain, and a great mind; in these things, I say, greatness is one thing, and that which is great because of greatness is another, and a great house, certainly, is not absolute greatness itself. But that is absolute greatness by which not only a great house is great, and any great mountain is great, but also by which every other thing whatsoever is great, which is called great; so that greatness itself is one thing, and those things are another which are called great from it. And this greatness certainly is primarily great, and in a much more excellent way than those things which are great by partaking of it. But since God is not great with that greatness which is not Himself, so that God, in being great, is, as it were, partaker of that greatness;--otherwise that will be a greatness greater than God, whereas there is nothing greater than God; therefore, He is great with that greatness by which He Himself is that same greatness. And, therefore, as we do not say three essences, so neither do we say three greatnesses; for it is the same thing to God to be, and to be great. For the same reason neither do we say three greats, but one who is great; since God is not great by partaking of greatness, but He is great by Himself being great, because He Himself is His own greatness. Let the same be said also of the goodness, and of the eternity, and of the omnipotence of God, and, in short, of all the predicaments which can be predicated of God, as He is spoken of in respect to Himself, not metaphorically and by similitude, but properly, if indeed anything can be spoken of Him properly, by the mouth of man.
Chapter 11.--What is Said Relatively in the Trinity.
12. But whereas, in the same Trinity, some things severally are specially predicated, these are in no way said in reference to themselves in themselves, but either in mutual reference, or in respect to the creature; and, therefore, it is manifest that such things are spoken relatively, not in the way of substance. For the Trinity is called one God, great, good, eternal, omnipotent; and the same God Himself may be called His own deity, His own magnitude, His own goodness, His own eternity, His own omnipotence: but the Trinity cannot in the same way be called the Father, except perhaps metaphorically, in respect to the creature, on account of the adoption of sons. For that which is written, "Hear, O Israel: the Lord our God is one Lord," [583] ought certainly not to be understood as if the Son were excepted, or the Holy Spirit were excepted; which one Lord our God we rightly call also our Father, as regenerating us by His grace. Neither can the Trinity in any wise be called the Son, but it can be called, in its entirety, the Holy Spirit, according to that which is written, "God is a Spirit;" [584] because both the Father is a spirit and the Son is a spirit, and the Father is holy and the Son is holy. Therefore, since the Father, the Son and the Holy Spirit are one God, and certainly God is holy, and God is a spirit, the Trinity can be called also the Holy Spirit. But yet that Holy Spirit, who is not the Trinity, but is understood as in the Trinity, is spoken of in His proper name of the Holy Spirit relatively, since He is referred both to the Father and to the Son, because the Holy Spirit is the Spirit both of the Father and of the Son. But the relation is not itself apparent in that name, but it is apparent when He is called the gift of God; [585] for He is the gift of the Father and of the Son, because "He proceeds from the Father," [586] as the Lord says; and because that which the apostle says, "Now, if any man have not the Spirit of Christ, he is none of His," [587] he says certainly of the Holy Spirit Himself. When we say, therefore, the gift of the giver, and the giver of the gift, we speak in both cases relatively in reciprocal reference. Therefore the Holy Spirit is a certain unutterable communion of the Father and the Son; and on that account, perhaps, He is so called, because the same name is suitable to both the Father and the Son. For He Himself is called specially that which they are called in common; because both the Father is a spirit and the Son a spirit, both the Father is holy and the Son holy. [588] In order, therefore, that the communion of both may be signified from a name which is suitable to both, the Holy Spirit is called the gift of both. And this Trinity is one God, alone, good, great, eternal, omnipotent; itself its own unity, deity, greatness, goodness, eternity, omnipotence.
[583] Deut. vi. 4
[584] John iv. 24
[585] Acts viii. 20
[586] John xv. 26
[587] Rom. viii. 9
[588] [The reason which Augustin here assigns, why the name Holy Spirit is given to the third person--namely, because spirituality is a characteristic of both the Father and Son, from both of whom he proceeds--is not that assigned in the more developed trinitarianism. The explanation in this latter is, that the third person is denominated the Spirit because of the peculiar manner in which the divine essence is communicated to him--namely, by spiration or out-breathing: spiritus quia spiratus. This is supported by the etymological signification of pneuma, which is breath; and by the symbolical action of Christ in John xx. 22, which suggests the eternal spiration, or out-breathing of the third person. The third trinitarian person is no more spiritual, in the sense of immaterial, than the first and second persons, and if the term "Spirit" is to be taken in this the ordinary signification, the "trinitarian relation," or personal peculiarity, as Augustin remarks, "is not itself apparent in this name;" because it would mention nothing distinctive of the third person, and not belonging to the first and second. But taken technically to denote the spiration or out-breathing by the Father and Son, the trinitarian peculiarity is apparent in the name. And the epithet "Holy" is similarly explained. The third person is the Holy Spirit, not because he is any more holy than the first and second, but because he is the source and author of holiness in all created spirits. This is eminently and officially his work. In this way also, the epithet "Holy"--which in its ordinary use would specify nothing peculiar to the third person,--mentions a characteristic that differentiates him from the Father and Son.--W.G.T.S.]