On the Christian Faith (De fide)

The author distinguishes the faith from the errors of Pagans, Jews, and Heretics, and after explaining the significance of the names “God” and “Lord,” shows clearly the difference of Persons in Unity of Essence. In dividing the Essence, the Arians not only bring in the doctrine of three Gods, but even overthrow the dominion of the Trinity.

6. Now this is the declaration of our Faith, that we say that God is One, neither dividing His Son from Him, as do the heathen, nor denying, with the Jews, that He was begotten of the Father before all worlds, and afterwards born of the Virgin; nor yet, like Sabellius, confounding the Father with the Word, and so maintaining that Father and Son are one and the same Person; nor again, as does Photinus, holding that the Son first came into existence in the Virgin's womb: nor believing, with Arius, in a number of diverse Powers, and so, like the benighted heathen, making out more than one God. For it is written: “Hear, O Israel: the Lord your God is one God.”

7. For God and Lord is a name of majesty, a name of power, even as God Himself says: “The Lord is My name,” and as in another place the prophet declares: “The Lord Almighty is His name.” God is He, therefore, and Lord, either because His rule is over all, or because He beholds all things, and is feared by all, without difference.

8. If, then, God is One, one is the name, one is the power, of the Trinity. Christ Himself, indeed, says: “Go, baptize the nations in the name of the Father, and of the Son, and of the Holy Spirit.” In the name, mark you, not in the names.

9. Moreover, Christ Himself says: “I and the Father are One.” “One,” said He, that there be no separation of power and nature; but again, “We are,” that you may recognize Father and Son, forasmuch as the perfect Father is believed to have begotten the perfect Son, and the Father and the Son are One, not by confusion of Person, but by unity of nature.

10. We say, then, that there is one God, not two or three Gods, this being the error into which the impious heresy of the Arians does run with its blasphemies. For it says that there are three Gods, in that it divides the Godhead of the Trinity; whereas the Lord, in saying, “Go, baptize the nations in the name of the Father and of the Son and of the Holy Spirit,” has shown that the Trinity is of one power. We confess Father, Son, and Spirit, understanding in a perfect Trinity both fullness of Divinity and unity of power.

11. “Every kingdom divided against itself shall quickly be overthrown,” says the Lord. Now the kingdom of the Trinity is not divided. If, therefore, it is not divided, it is one; for that which is not one is divided. The Arians, however, would have the kingdom of the Trinity to be such as may easily be overthrown, by division against itself. But truly, seeing that it cannot be overthrown, it is plainly undivided. For no unity is divided or rent asunder, and therefore neither age nor corruption has any power over it.