But if 'essence' is not a special name but a general one, since a man and a beast and a tree and a star and an angel are called 'essence,' why are these not called 'three essences,' as three horses are called 'three animals' and three laurels are called 'three trees' and three stones 'three bodies'? Or if, on account of the unity of the Trinity, they are not called 'three essences' but 'one essence,' why, on account of the same unity, are they not called not 'three substances' or 'three persons' but 'one substance' and 'one person'? For as common to them is the name of 'essence,' so that each single one is called 'essence,' so common to them is the term 'substance' or 'person.'
For what we have said concerning 'persons' according to our usage, this must be understood concerning 'substances' according to the usage of the Greeks. For they say 'three substances, one essence' in the same way that we say 'three persons, one essence or substance.' What, then, remains? Shall we confess that these terms were brought forth by the necessity of speaking, when there was need of a copious disputation against the snares or errors of the heretics? For when human poverty tried to bring forth in speech, for the perception of men, that which it holds in the inner chamber of the mind as far as its grasp allows concerning the Lord God its Creator, whether through pious faith or through some understanding of any sort, it feared to say 'three essences,' lest any diversity should be understood in that supreme equality.
Again, it could not say that they are not three certain things — which, because Sabellius said it, he fell into heresy. For it is most certainly known both from the Scriptures what must be piously believed, and it is grasped by the gaze of the mind with undoubting perception, that the Father is, and the Son is, and the Holy Spirit is, and that the Son is not the same as the Father, nor is the Holy Spirit the same as the Father or the Son. It sought what to call the three, and said 'substances' or 'persons,' by which names it wished not diversity to be understood, but singleness to be denied, so that not only unity should be there understood from what is called 'one essence,' but also Trinity from what are called 'three substances or persons.'
For if to be God is the same as to subsist, then three substances ought no more to be spoken of than three essences are spoken of; just as, because to be God is the same as to be wise, so, as we do not say three essences, neither do we say three wisdoms. For thus, because for him to be God is the same as to be, it is no more lawful to say three essences than three Gods. But if to be God is one thing, to subsist another — as to be God is one thing, to be Father or to be Lord another (for what he is is said with respect to himself, but 'Father' is said with respect to the Son and 'Lord' with respect to the creature that serves; therefore he subsists relatively, as he begets relatively and rules relatively) — then substance will no longer be substance, since it will be relative.
For just as from that which is 'to be' comes the name 'essence,' so from that which is 'to subsist' we call it 'substance.' But it is absurd that substance should be spoken of relatively; for every thing subsists with respect to itself. How much more God — [V 10] if indeed it is fitting that God be said to subsist? For 'to subsist' is rightly understood of those things in which, as subjects, are those things which are said to be in some subject, as color or shape in a body. For a body subsists, and therefore is a substance; but those things are in the subsisting and underlying body, which are not substances but are in a substance;
and therefore if either that color or that shape should cease to be, they do not deprive the body of being a body, since to retain this or that shape or color is not the same for it as to be. Therefore mutable and non-simple things are properly called substances. But if God subsists so that he can properly be called a substance, there is in him something as in a subject, and he is not simple, for whom to be is the same as whatever is said of him with respect to himself, such as 'great,' 'omnipotent,' 'good,' and if anything of this kind is said of God not unfittingly. But it is impious to say that God subsists and underlies his own goodness, and that goodness is not a substance or rather an essence, and that God himself is not his own goodness, but that it is in him as in a subject.
Whence it is manifest that God is called 'substance' by an abuse of the term, so that by a more customary name 'essence' may be understood, which is truly and properly said, so that perhaps God alone ought to be called 'essence.' For he alone truly is, because he is unchangeable, and this his name he declared to his servant Moses when he said: 'I am who I am,' and 'You shall say to them: He who is has sent me to you.' Yet whether it be called 'essence,' which is said properly, or 'substance,' which is said by abuse, both are said with respect to himself, not relatively to something. Hence for God to be is the same as to subsist, and therefore if the Trinity is one essence, it is also one substance. Perhaps, then, 'three persons' is more fittingly said than 'three substances.'
[VI 11] But lest this too should seem to favor us, let us inquire; although they too, if they wished, just as they say 'three substances,' *treis hypostaseis, could say 'three persons,' *tria prosopa. But they preferred that word which perhaps, according to the custom of their own language, was more aptly said. For in the case of 'persons' too the same reasoning holds; for it is not one thing for God to be, and another to be a person, but altogether the same. For if 'to be' is said with respect to himself, but 'person' relatively. Thus let us say 'three persons,' the Father and the Son and the Holy Spirit, just as some are called 'three friends' or 'three kinsmen' or 'three neighbors,' because they are so with respect to one another, not because each of them is so with respect to himself.
Wherefore any one of them is friend of the other two, or kinsman or neighbor, because these names have a relative signification. What then? Does it please us to say that the Father is the person of the Son and of the Holy Spirit, or that the Son is the person of the Father and of the Holy Spirit, or that the Holy Spirit is the person of the Father and of the Son? But neither is 'person' anywhere wont to be so said, nor, in this Trinity, when we say 'the person of the Father,' do we mean anything other than the substance of the Father. Wherefore, as the substance of the Father is the Father himself, not in that he is Father but in that he is, so also the person of the Father is nothing other than the Father himself. For 'person' is said with respect to himself, not with respect to the Son or the Holy Spirit;
just as 'God' and 'great' and 'good' and 'just' and anything else of this kind is said with respect to himself. And as for him to be is the same as to be God, or to be great, or to be good, so for him to be is the same as to be a person. Why, then, do we not say that these three together are one person, as they are one essence and one God, but say 'three persons,' though we do not say 'three Gods' or 'three essences,' except because we wish some one term at least to serve this signification by which the Trinity is understood, lest we should be altogether silent when asked what three, since we confessed that there are three?
For if 'essence' is the genus, and 'substance' or 'person' the species, as some think (I pass over what I have already said, that they ought to be called 'three essences' as they are called 'three substances or persons,' just as 'three horses' are called 'three animals,' since 'horse' is a species and 'animal' a genus. For neither is the species there said in the plural and the genus in the singular, as though it were said 'three horses, one animal,' but as 'three horses' by a special name, so 'three animals' by a general name.
But if they say that by the name of 'substance' or 'person' not a species is signified but something singular and individual, so that 'substance' or 'person' is not said as 'man' is said, which is common to all men, but as 'this man' is said — such as Abraham, such as Isaac, such as Jacob, or if there be any other who could even be pointed out present with the finger — then in this way too the same reasoning will follow for them. For as Abraham, Isaac, Jacob are called 'three individuals,' so 'three men' and 'three souls.' Why then, if we discuss these things too according to genus and species and individual, are the Father and the Son and the Holy Spirit not so called 'three essences' as 'three substances or persons'? But this, as I said, I pass over).
This I say: if 'essence' is a genus, then one essence no longer has species, just as, because 'animal' is a genus, one animal no longer has species. The Father and the Son and the Holy Spirit, therefore, are not three species of one essence. But if 'essence' is a species, as 'man' is a species, and those three which we call substances or persons commonly have the same species in the way that Abraham and Isaac and Jacob commonly have the species which is called 'man' (not as 'man' is subdivided into Abraham, Isaac and Jacob, so one man can also be subdivided into some single men; for it altogether cannot, since one man is already a single man): why, then, is one essence subdivided into three substances or persons?
For if 'essence' is a species, as 'man' is, then one essence is as one man. Or, as we say that some three men of the same sex, of the same bodily constitution, and of the same disposition of mind are one nature (for they are three men but one nature), do we likewise there say 'three substances, one essence,' or 'three persons, one substance or essence'? This indeed is in some way similar, because the ancients also who spoke Latin, before they had these names — which came into use not long ago, that is 'essence' or 'substance' — used to say 'nature' for these. Therefore we say these things not according to genus and species, but as according to a common and identical matter.
Just as, if three statues were made from the same gold, we would say 'three statues, one gold,' yet we would not call gold the genus and statues the species; nor gold the species and statues the individuals. For no species passes beyond its own individuals so as to comprehend something outside them. For when I have defined what 'man' is, which is a special name, the single individual men, which are individuals, are contained by the same definition, nor does anything pertain to it which is not a man. But when I have defined 'gold,' not only statues, if they be of gold, but also rings and whatever else may be of gold, will pertain to gold. And even if nothing be made of it, it is called gold, because even if they were not of gold, they would not for that reason cease to be statues.
Likewise no species exceeds the definition of its own genus. For when I have defined 'animal,' since 'horse' is a species of this genus, every horse is an animal; but not every statue is gold. Therefore, although in three golden statues we rightly say 'three statues, one gold,' yet we do not say it in such a way as to understand gold as the genus and statues as the species. Nor, then, do we call the Trinity 'three persons or substances, one essence and one God' as though three certain things subsist out of one matter, even if whatever that is were unfolded in these three; for there is nothing else of that essence besides this Trinity. Yet we say 'three persons of the same essence,' or 'three persons, one essence';
but we do not say 'three persons out of the same essence,' as if there were one thing there which is essence and another which is person, as we can say 'three statues out of the same gold'; for there it is one thing to be gold, another to be statues. And when 'three men, one nature' or 'three men of the same nature' are spoken of, they can also be called 'three men out of the same nature,' since out of the same nature other such men can also come to exist; but in that essence of the Trinity, in no way can any other person whatsoever come to exist out of the same essence. Furthermore, in these things one man is not as much as three men together, and two men are something more than one man;
and in equal statues there is more gold in three together than in single ones, and less gold in one than in two. But in God it is not so; for the Father and the Son together are not a greater essence than the Father alone or the Son alone, but those three substances or persons together, if they are to be so called, are equal to the single ones — which the animal man does not perceive. For he cannot think except of masses and spaces, whether small or great, phantasms flitting in his mind like images of bodies.
From which uncleanness, until he be purged, let him believe in the Father and the Son and the Holy Spirit, one God, alone, great, omnipotent, good, just, merciful, Creator of all things visible and invisible, and whatever can be worthily and truly said of him according to human capacity. Nor, when he hears 'the Father alone is God,' let him separate the Son or the Holy Spirit from him; for with him he is the only God, with whom he is also one God — since when we hear that the Son also is the only God, we must accept it without any separation of the Father or the Holy Spirit.
And so let him speak of 'one essence' in such a way that he does not suppose one to be greater or better than another, or in any part diverse; yet not so that the Father himself should be both the Son and the Holy Spirit, and whatever else the single ones are called with respect to one another, as 'Word,' which is said only of the Son, or 'gift,' which is said only of the Holy Spirit. For which reason they also admit the plural number, as it is written in the Gospel: 'I and the Father are one.' He said both 'one' and 'are'; 'one' according to essence, because they are the same God; 'are' according to the relative, because that one is Father, this one Son. Sometimes even the unity of essence is passed over in silence, and the relatives alone are mentioned in the plural: 'We will come to him, I and the Father, and will make our abode with him.'
'We will come and make our dwelling' is a plural in number, because it was foretold, 'I and the Father'—that is, the Son and the Father—which are terms spoken relatively to one another. Sometimes it is done wholly in a hidden way, as in Genesis: 'Let us make man to our own image and likeness.' Both 'let us make' and 'our own' are spoken in the plural, and they must not be taken otherwise than from what is relative. For it was not that gods might make him, nor to the image and likeness of gods, but that the Father and the Son and the Holy Spirit might make him; therefore to the image of the Father and of the Son and of the Holy Spirit, so that man might subsist as the image of God—and God is Trinity.
But since that image of God was not made wholly equal, being not born of Him but created by Him, to signify this it is an image in such a way that it is 'to the image'—that is, it is not made equal by parity, but approaches Him by a certain likeness. For one draws near to God not by intervals of place but by likeness, and withdraws from Him by unlikeness. There are indeed those who so distinguish that they would have the Son to be the Image, but man to be not the image but 'to the image.' Yet the Apostle refutes them, saying: 'A man indeed ought not to veil his head, since he is the image and glory of God.' He did not say 'to the image' but 'image.' Yet this image, when elsewhere it is said to be 'to the image,' is not said as though with reference to the Son, whose image is equal to the Father;
otherwise it would not say 'to our image.' For how could it say 'our,' when the Son is the image of the Father alone? But on account of that unequal likeness, as we have said, man was called 'to the image'; and therefore 'our,' so that man might be the image of the Trinity—not equal to the Trinity as the Son is to the Father, but approaching it, as was said, by a certain likeness, just as among things far apart a certain nearness is signified, not of place but of a kind of imitation. For to this end it is also said: 'Be renewed in the newness of your mind'; and to the same it says: 'Be therefore imitators of God, as most beloved sons.' For it is said to the new man: 'who is renewed unto the knowledge of God according to the image of Him that created him.'
Or if, for the sake of the necessity of discussion, it now be permitted—even apart from the relative names—to admit the plural number, so that when it is asked what the three are, one may answer with a single name and say three substances or persons: let no masses or intervals be conceived, no distance of any degree of unlikeness whatever, nor let it be understood that one is anything other than another, or even a little less in any manner whatsoever than another, in such a way that there be neither confusion of persons nor such distinction whereby anything should be unequal. But if this cannot be grasped by the understanding, let it be held by faith, until He shine forth in our hearts who said through the prophet: 'Unless you believe, you shall not understand.'