Tertullian

“ When He was asked by the Jews if He were the very Christ [24] (meaning, of course, the Christ of God; for to this day the Jews expect not the Father Himself, but the Christ of God, it being nowhere said that the Father will come as the Christ) , He said to them, “I am telling you, and yet ye do not believe: the works which I am doing, in my Father’s name, they actually bear witness of me.” ”

“ Unus, no doubt, indicates the singular number; but (here we have a case where) “Two” are still the subject in the masculine gender. He accordingly says Unum, a neuter term, which does not imply singularity of number, but unity of essence, likeness, conjunction, affection on the Father’s part, who loves the Son, and submission on the Son’s, who obeys the Father’s will. When He says, “I and my Father are one” in essence—Unum—He shows that there are Two, whom He puts on an equality and unites in one. ”

“ If I do not the works of my Father, believe me not; but if I do, even if ye will not believe me, still believe the works; and know that I am in the Father, and the Father in me.” [30] It must therefore be by the works that the Father is in the Son, and the Son in the Father; and so it is by the works that we understand that the Father is one with the Son. All along did He therefore strenuously aim at this conclusion, that while they were of one power and essence, they should still be believed to be Two ”