Here's a beef of mine - when people almost completely reverse Gregory of Nazianzus's famous trinity quote while expressing admiration for it. You know the one...
"I cannot think on the one without quickly being encircled by the splendor of the three nor can I discern the three without being straightway carried back to the one.".
I too love the quote. But many times this is what the quotation is wheeled out to mean:
When I spend 600 pages of my systematic theology expounding a simple divine essence I then force myself to examine the Persons and when I've had enough of discussing the Persons I gleefully return to the omnibeing.
After I've thought of the god of monotheism for a bit I make sure I spend at least as long thinking about the gospel. And once I'm done thinking about the gospel, then I make sure I think about that other idea - you know, god's oneness.
Here's how I reckon the reversal happens. First people take Gregory to be saying something very basic - i.e. the One and the Three are 'equally ultimate' (or, if you're really posh, equiprimordial!). Then you run away with the 'equally ultimate' thought and think of it as some kind of 'equal air time' agreement between competing political parties.
But first of all, Gregory is saying something much more than that basic thought. Look again at the 'cannot', the 'being encircled' and the 'carried back.' Gregory is not forcing himself to give equal air time to One and Three. Gregory says that the Oneness of God actually gives him the Three. And the Three give Him the Oneness. It's not that he's ensuring equal treatment, he doesn't need to turn from a consideration of Oneness to a consideration of Threeness. It's a right contemplation of the Oneness of God itself that presents him with the Three. And the Three simply present to him as the One God.
This is how the One and the Three are related. The One God simply is the loving unity of those Three Persons. And those Three Persons simply are without remainder who this One God is.
Trinity simply means 'unity of three'. That's how the One and the Three are co-ordinated. They are not separate topics to be separately studied. You cannot talk about the One God if you're not talking about the Three Persons who are the One God. That's the radical importance of Gregory's insight.
Now go and re-write those 600 pages.