Peter Leithart has two great posts wrestling with some of Augustine’s questions about the nature of the relations within the Trinity and the question of simplicity, particularly his struggles with the biblical affirmation that Christ is “the power of God and the wisdom of God.” Augustine labors mightily to articulate how this can be true if the Father is supposed to have these qualities himself. Leithart throws out one provocative possible solution:
Does the Father have wisdom “in Himself”? Yes, because the Wisdom that is the Son dwells in Him by the Spirit. Does the Father possess His being “in Himself”? Yes, because the Son is the fullness of His deity, and the Son indwells Him through the Spirit. Vice versa: Does the Son have wisdom considered in Himself? Yes, because what is “in Himself” is the fact that the Father dwells in Him in the Spirit, so that His existence “in Himself” is His existence as the Son indwelt by the Father.
And so on.
This allows us to speak of Father and Son distinctly; it also makes it clear that the Father is not Himself except as He has and is indwelt by His Son, nor is the Son Himself except as He has and is indwelt the Father.
To me this seems like a necessary critique of any sort of pyramidal trinitarianism like that articulated by John Zizioulas, for example.