Therefore, if they have determined that the Father and the Son must be regarded as one and the same, for the express purpose of vindicating the unity of God, that unity of His is preserved intact; for He is one, and yet He has a Son, who is equally with Himself comprehended in the same Scriptures. Since they are unwilling to allow that the Son is a distinct Person, second from the Father, lest, being thus second, He should cause two Gods to be spoken of, we have shown above that Two are actually described in Scripture as God and Lord. And to prevent their being offended at this fact, we give a reason why they are not said to be two Gods and two Lords, but that they are two as Father and Son; and this not by severance of their substance, but from the dispensation wherein we declare the Son to be undivided and inseparable from the Father,—distinct in degree, not in state. And although, when named apart, He is called God, He does not thereby constitute two Gods, but one; and that from the very circumstance that He is entitled to be called God, from His union with the Father.
Tertullian
Against Praxeas
Chapter XIX