Gregory Nazianzen on the Trinity
This I give you to share, and to defend all your life, the one Godhead and power, found in the three in unity, and comprising the three separately; not unequal, in substances or natures, neither increased nor diminished by superiorities or inferiorities; in every respect equal, in every respect the same; just as the beauty and the greatness of the heavens is one; the infinite conjunction of three infinite ones, each God when considered in himself; as the Father, so the Son; as the Son, so the Holy Spirit; the three one God when contemplated together; each God because consubstantial; one God because of the monarchia. No sooner do I conceive of the one than I am illumined by the splendour of the three; no sooner do I distinguish them than I am carried back to the one. When I think of any one of the three I think of him as the whole, and my eyes are filled, and the greater part of what I am thinking escapes me. I cannot grasp the greatness of that one so as to attribute a greater greatness to the rest. When I contemplate the three together, I see but one torch, and cannot divide or measure out the undivided light. — Gregory Nazianzen, Oration on Holy Baptism
As quoted by Robert Letham in The Holy Trinity.