Tertullian · a new plain-English translation from the original language
Having professed this rule, by which I maintain that Father, Son, and Spirit cannot be pulled apart from one another, keep this always before you, and so you will understand in what sense each statement is made. For observe: I say that the Father is one, the Son another, and the Spirit another — a phrase every ignorant or perverse person misconstrues, as though it meant diversity, and as though from that diversity it implied a separation of Father, Son, and Spirit. I say this out of necessity, since there are those who, in order to flatter the Monarchy, contend that Father, Son, and Spirit are one and the very same thing, working against the order of the Economy. The Son is other than the Father not by diversity but by distribution; not by division but by distinction — because the Father and the Son are not one and the same, though each differs from the other not in kind but in degree. For the Father is the whole substance, while the Son is a derivation and portion of the whole, as he himself declares: "Because the Father is greater than I." By him, too, he is sung as made lower, in the psalm: "A little lower than the angels." So too the Father is other than the Son, in that he is greater than the Son; in that the one who begets is other than the one who is begotten; in that the one who sends is other than the one who is sent; in that the one who acts is other than the one through whom it is done. And it is well that the Lord himself used this same word in speaking of the Paraclete's person, signifying not division but arrangement: "For I will ask the Father," he says, "and he will send you another Advocate, the Spirit of truth." Thus he showed the Paraclete to be other than himself, in the same way we say the Son is other than the Father — so as to show a third rank in the Paraclete, just as we show a second in the Son, on account of the order that governs the Economy. Indeed, the very fact that they are called Father and Son — is that not itself a case of one being other than the other? Certainly whatever things are, will be called by what they are called, and will be what they are called; and there can be no confusing the diversity of their names at all, because there can be no confusing the diversity of the realities they name. Let your "yes" be yes, and your "no," no; for whatever is more than this comes from evil.