It does not seem to me absolutely necessary, with a view to the present proof of our argument, to contend against those who oppose us with the assertion that we are not to conceive “Godhead” as an operation. For we, believing the Divine nature to be unlimited and incomprehensible, conceive no comprehension of it, but declare that the nature is to be conceived in all respects as infinite: and that which is absolutely infinite is not limited in one respect while it is left unlimited in another, but infinity is free from limitation altogether. That therefore which is without limit is surely not limited even by name. In order then to mark the constancy of our conception of infinity in the case of the Divine nature, we say that the Deity is above every name: and “Godhead” is a name. Now it cannot be that the same thing should at once be a name and be accounted as above every name.
But if it pleases our adversaries to say that the significance of the term is not operation, but nature, we shall fall back upon our original argument, that custom applies the name of a nature to denote multitude erroneously: since according to true reasoning neither diminution nor increase attaches to any nature, when it is contemplated in a larger or smaller number. For it is only those things which are contemplated in their individual circumscription which are enumerated by way of addition. Now this circumscription is noted by bodily appearance, and size, and place, and difference figure and colour, and that which is contemplated apart from these conditions is free from the circumscription which is formed by such categories. That which is not thus circumscribed is not enumerated, and that which is not enumerated cannot be contemplated in multitude. For we say that gold, even though it be cut into many figures, is one, and is so spoken of, but we speak of many coins or many staters, without finding any multiplication of the nature of gold by the number of staters; and for this reason we speak of gold, when it is contemplated in greater bulk, either in plate or in coin, as “much,” but we do not speak of it as “many golds” on account of the multitude of the material—except when one says there are “many gold pieces” (Darics, for instance, or staters), in which case it is not the material, but the pieces of money to which the significance of number applies: indeed, properly, we should not call them “gold” but “golden.”
As, then, the golden staters are many, but the gold is one, so too those who are exhibited to us severally in the nature of man, as Peter, James, and John, are many, yet the man in them is one. And although Scripture extends the word according to the plural significance, where it says “men swear by the greater,” and “sons of men,” and in other phrases of the like sort, we must recognize that in using the custom of the prevailing form of speech, it does not lay down a law as to the propriety of using the words in one way or another, nor does it say these things by way of giving us instruction about phrases, but uses the word according to the prevailing custom, with a view only to this, that the word may be profitable to those who receive it, taking no minute care in its manner of speech about points where no harm can result from the phrases in respect of the way they are understood.
Indeed, it would be a lengthy task to set out in detail from the Scriptures those constructions which are inexactly expressed, in order to prove the statement I have made; where, however, there is a risk of injury to any part of the truth, we no longer find in Scriptural phrases any indiscriminate or indifferent use of words. For this reason Scripture admits the naming of “men” in the plural, because no one is by such a figure of speech led astray in his conceptions to imagine a multitude of humanities, or supposes that many human natures are indicated by the fact that the name expressive of that nature is used in the plural. But the word “God” it employs studiously in the singular form only, guarding against introducing the idea of different natures in the Divine essence by the plural signification of “Gods.” This is the cause why it says, “the Lord our God is one Lord,” and also proclaims the Only-begotten God by the name of Godhead, without dividing the Unity into a dual signification, so as to call the Father and the Son two Gods, although each is proclaimed by the holy writers as God. The Father is God: the Son is God: and yet by the same proclamation God is One, because no difference either of nature or of operation is contemplated in the Godhead. For if (according to the idea of those who have been led astray) the nature of the Holy Trinity were diverse, the number would by consequence be extended to a plurality of Gods, being divided according to the diversity of essence in the subjects. But since the Divine, single, and unchanging nature, that it may be one, rejects all diversity in essence, it does not admit in its own case the signification of multitude; but as it is called one nature, so it is called in the singular by all its other names, “God,” “Good,” “Holy,” “Saviour,” “Just,” “Judge,” and every other Divine name conceivable: whether one says that the names refer to nature or to operation, we shall not dispute the point.
If, however, any one cavils at our argument, on the ground that by not admitting the difference of nature it leads to a mixture and confusion of the Persons, we shall make to such a charge this answer—that while we confess the invariable character of the nature, we do not deny the difference in respect of cause, and that which is caused, by which alone we apprehend that one Person is distinguished from another—by our belief, that is, that one is the Cause, and another is of the Cause; and again in that which is of the Cause we recognize another distinction. For one is directly from the first Cause, and another by that which is directly from the first Cause; so that the attribute of being Only-begotten abides without doubt in the Son, and the interposition of the Son, while it guards His attribute of being Only-begotten, does not shut out the Spirit from His relation by way of nature to the Father.
But in speaking of “cause,” and “of the cause,” we do not by these words denote nature (for no one would give the same definition of “cause” and of “nature”), but we indicate the difference in manner of existence. For when we say that one is “caused,” and that the other is “without cause,” we do not divide the nature by the word “cause”, but only indicate the fact that the Son does not exist without generation, nor the Father by generation: but we must needs in the first place believe that something exists, and then scrutinize the manner of existence of the object of our belief: thus the question of existence is one, and that of the mode of existence is another. To say that anything exists without generation sets forth the mode of its existence, but what exists is not indicated by this phrase. If one were to ask a husbandman about a tree, whether it were planted or had grown of itself, and he were to answer either that the tree had not been planted or that it was the result of planting, would he by that answer declare the nature of the tree? Surely not; but while saying how it exists he would leave the question of its nature obscure and unexplained. So, in the other case, when we learn that He is unbegotten, we are taught in what mode He exists, and how it is fit that we should conceive Him as existing, but what He is we do not hear in that phrase. When, therefore, we acknowledge such a distinction in the case of the Holy Trinity, as to believe that one Person is the Cause, and another is of the Cause, we can no longer be accused of confounding the definition of the Persons by the community of nature.
Thus, since on the one hand the idea of cause differentiates the Persons of the Holy Trinity, declaring that one exists without a Cause, and another is of the Cause; and since on the one hand the Divine nature is apprehended by every conception as unchangeable and undivided, for these reasons we properly declare the Godhead to be one, and God to be one, and employ in the singular all other names which express Divine attributes.
Source: On "Not Three Gods" (To Ablabius) (New Advent)