19. The Lord always maintained this definition of the faith of the Church, which consists in teaching that there is one God the Father, but without separating Himself from the mystery of the one God, for He declared Himself, by the nature which is His by birth, neither a second God, nor the sole God. Since the nature of the One God is in Him, He cannot be God of a different kind from Him; His birth requires that, being Son, it should be with a perfect Sonship i.e. including personal distinction from the Father, cf. c. 1, and note.. So He can neither be separated from God nor merged in God. Hence He speaks in words deliberately chosen, so that whatever He claims for the Father, He signifies in modest language to be appropriate to Himself also. Take as an instance the command, Believe in God, and believe also in Me St. John xiv. 1.. He is identified with God in honour; how, pray, can He be separated from His nature? He says, Believe in Me also, just as He said Believe in God. Do not the words in Me signify His nature? Separate the two natures, but you must separate also the two beliefs. If it be life, that we should believe in God without Christ, strip Christ of the name and qualities of God. But if perfect life is given to those who believe in God, only when they believe in Christ also, let the careful reader ponder the meaning of the saying, Believe in God, and believe in Me also, for these words, uniting faith in Him with faith in God, unite His nature to God’s. He enjoins first of all the duty of belief in God, but adds to it the command that we should believe in Himself also; which implies that He is God, since they who believe in God must also believe in Him. Yet He excludes the suggestion of a unity contrary to religion i.e. such as Sabellius had taught by extending the unity of nature into a unity of person. There is a unity of nature in the Godhead, but a union of Persons., for the exhortation Believe in God, believe in Me also, forbids us to think of Him as alone in solitude.