2 But we who have attained this wisdom of God, which is folly to the world, and purpose, by means of the sound and saving profession of true faith in the Lord, to unmask the snake-like treachery of their teaching; we have so laid out the plan of our undertaking as to gain a vantage ground for the display of the truth without entangling ourselves in the dangers of heretical assertion. We carefully avoid either extreme; not denying that God is One, yet setting forth distinctly, on the evidence of the Lawgiver who proclaims the unity of God, the truth that there is God and God.
We teach that it is by no confusion of the Two that God is One; we do not rend Him in pieces by preaching a plurality of Gods, nor yet do we profess a distinction only in name. But we present Him as God and God, postponing at present for fuller discussion hereafter the question of the Divine unity. For the Gospels tell us that Moses taught the truth when he proclaimed that God is One; and Moses by his proclamation of One God confirms the lesson of the Gospels, which tell of God and God.
Thus we do not contradict our authorities, but base our teaching upon them, proving that the revelation to Israel of the unity of God gives no sanction to the refusal of Divinity to the Son of God; since he who is our authority for asserting that there is One God is our authority also for confessing the Godhead of His Son.
Source: On the Trinity (New Advent)