The Divine Institutes

Some one may perhaps ask how, when we say that we worship one God only, we nevertheless assert that there are two, God the Father and God the Son: which assertion has driven many into the greatest error. For when the things which we say seem to them probable, they consider that we fail in this one point alone, that we confess that there is another God, and that He is mortal. We have already spoken of His mortality: now let us teach concerning His unity. When we speak of God the Father and God the Son, we do not speak of them as different, nor do we separate each: because the Father cannot exist without the Son, nor can the Son be separated from the Father, since the name of Father cannot be given without the Son, nor can the Son be begotten without the Father. Since, therefore, the Father makes the Son, and the Son the Father, they both have one mind, one spirit, one substance; but the former is as it were an overflowing fountain, the latter as a stream flowing forth from it: the former as the sun, the latter as it were a ray extended from the sun. And since He is both faithful to the Most High Father, and beloved by Him, He is not separated from Him; just as the stream is not separated from the fountain, nor the ray from the sun: for the water of the fountain is in the stream, and the light of the sun is in the ray: just as the voice cannot be separated from the mouth, nor the strength or hand from the body. When, therefore, He is also spoken of by the prophets as the hand, and strength, and word of God, there is plainly no separation; for the tongue, which is the minister of speech, and the hand, in which the strength is situated, are inseparable portions of the body.

We may use an example more closely connected with us. When any one has a son whom he especially loves, who is still in the house, and in the power of his father, although he concede to him the name and power of a master, yet by the civil law the house is one, and one person is called master. So this world is the one house of God; and the Son and the Father, who unanimously inhabit the world, are one God, for the one is as two, and the two are as one. Nor is that wonderful, since the Son is in the Father, for the Father loves the Son, and the Father is in the Son; for He faithfully obeys the will of the Father, nor does He ever do nor has done anything except what the Father either willed or commanded. Lastly, that the Father and the Son are but one God, Isaiah showed in that passage which we have brought forward before, when he said: “They shall fall down unto You, and make supplication unto You, since God is in You, and there is no other God besides You.” And he also speaks to the same purport in another place: “Thus says God the King of Israel, and His Redeemer, the everlasting God; I am the first, and I am the last; and beside me there is no God.” When he had set forth two persons, one of God the King, that is, Christ, and the other of God the Father, who after His passion raised Him from the dead, as we have said that the prophet Hosea showed, who said, “I will redeem Him from the power of the grave:” nevertheless, with reference to each person, he introduced the words, “and beside me there is no God,” when he might have said “beside us;” but it was not right that a separation of so close a relationship should be made by the use of the plural number. For there is one God alone, free, most high, without any origin; for He Himself is the origin of all things, and in Him at once both the Son and all things are contained. Wherefore, since the mind and will of the one is in the other, or rather, since there is one in both, both are justly called one God; for whatever is in the Father flows on to the Son, and whatever is in the Son descends from the Father. Therefore that highest and matchless God cannot be worshipped except through the Son. He who thinks that he worships the Father only, as he does not worship the Son, so he does not worship even the Father. But he who receives the Son, and bears His name, he truly together with the Son worships the Father also, since the Son is the ambassador, and messenger, and priest of the Most High Father. He is the door of the greatest temple, He the way of light, He the guide to salvation, He the gate of life.