Against Praxeas by Tertullian
Chapter IX.--The Catholic Rule of Faith Expounded in Some of Its Points Especially in the Unconfused Distinction of the Several Persons of the Blessed Trinity.
Bear always in mind that this is the rule of faith which I profess; by it I testify that the Father, and the Son, and the Spirit are inseparable from each other, and so will you know in what sense this is said. Now, observe, my assertion is that the Father is one, and the Son one, and the Spirit one, and that They are distinct from Each Other. This statement is taken in a wrong sense by every uneducated as well as every perversely disposed person, as if it predicated a diversity, in such a sense as to imply a separation among the Father, and the Son, and the Spirit. I am, moreover, obliged to say this, when (extolling the Monarchy at the expense of the Economy) they contend for the identity of the Father and Son and Spirit, that it is not by way of diversity that the Son differs from the Father, but by distribution: it is not by division that He is different, but by distinction; because the Father is not the same as the Son, since they differ one from the other in the mode of their being. For the Father is the entire substance, but the Son is a derivation and portion of the whole, as He Himself acknowledges: |My Father is greater than I.| In the Psalm His inferiority is described as being |a little lower than the angels.| Thus the Father is distinct from the Son, being greater than the Son, inasmuch as He who begets is one, and He who is begotten is another; He, too, who sends is one, and He who is sent is another; and He, again, who makes is one, and He through whom the thing is made is another. Happily the Lord Himself employs this expression of the person of the Paraclete, so as to signify not a division or severance, but a disposition (of mutual relations in the Godhead); for He says, |I will pray the Father, and He shall send you another Comforter...even the Spirit of truth,| thus making the Paraclete distinct from Himself, even as we say that the Son is also distinct from the Father; so that He showed a third degree in the Paraclete, as we believe the second degree is in the Son, by reason of the order observed in the Economy. Besides, does not the very fact that they have the distinct names of Father and Son amount to a declaration that they are distinct in personality? For, of course, all things will be what their names represent them to be; and what they are and ever will be, that will they be called; and the distinction indicated by the names does not at all admit of any confusion, because there is none in the things which they designate. |Yes is yes, and no is no; for what is more than these, cometh of evil.|