Gregory of Nazianzus on the Trinity

When it comes to reflecting on the Trinity the patristics are in a league of their own.

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 of 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.

Quote from Oration 40 (Nicene and Post-Nicene Fathers: Second Series, edited by Philip Schaff and Henry Wace)