In books 6-7 of The Trinity, Augustine teases out the meaning of 1 Corinthians 1:24, which identifies Christ as the Wisdom and Power of God. Is, Augustine asks, Christ the Son the Wisdom by which the Father is wise, or the Power by which the Father is powerful? He muses and ponders, but ultimately rejects that claim because he cannot see how a Father who is without Wisdom could generate or beget Wisdom. The Father must have Wisdom of His own to share it with the Son.
Athanasius takes the opposite view, and I think Athanasius is right, that on several grounds. First, Augustine’s counter-argument depends on isolating the Father in himself and considering the Father’s divine attributes without considering His Son and Spirit. But the Father is Father only by virtue of having Son, so there is no way to consider the Father “in himself.”
Second, Augustine’s logic could also be applied to the claim that the Son is the Word of God: Does the Father have “His own” word that is not the Word that is the Son? On Augustine’s reasoning, it seems that He must have, since how could He generate/beget the Word that is the Son if He were “in Himself” wordless? That damages the thrust of the biblical identification of the Son as Word, and has the strange effect of doubling the Second Person (and, by the same logic, the Third). Third, Augustine’s argument has the effect of pushing toward tritheism, a paradoxical result considering Augustine’s reputation as a unity-guy. If the Father, considered in isolation, is all that God is, then what is the need of three? Of course, each Person is fully God, but that is true because one cannot consider any of them in isolation; each is fully God as each communes with the others in an eternal life of love.
Finally, Augustine’s argument suggests that the Persons are not only equal and equally God, but identically God. In Book 6, Augustine muses on the Nicene formula, “light from light.” If the Father were not Light, then He could not beget the Light that is the Son. Athanasius makes much of the “light from light” imagery, but within that image he recognizes a differentiation: The Father is light as source, the Son light as radiance from the source. Again, Augustine’s argument, which tends to blur distinctions among the Persons, carries paradoxically tritheistic implications.
If Athanasius is right, it doesn’t mean that the Father is Wordless or Wisdomless. His Word and Wisdom, which is the Son, is eternal and eternally His. There’s not a foolish God who becomes wise by begetting a Son; that is precisely Athanasius’s point in using 1 Corinthians 1:24 against the Arians. It’s not that the Father is witless until He begets the Son; precisely because it is an insult to say God is witless, we must say that the Son who is Wisdom is eternally and necessarily begotten. Augustine’s logic, again paradoxically, seems to assume a before and after: The Father must be antecedently wise to beget Wisdom. Pressed, that would be an Arian position. If the Father isn’t wise by the Wisdom He begets, then Athanasius’s argument crumbles.
That the Word and Wisdom that is eternally the Father’s is a second Person of the Trinity means that the Father is eternally wise and wordful only insofar as He eternally begets Word and Wisdom, that the Father is wise and wordful only as He is with another. He is not wise and wordful in Himself because no such Father-in-Himself exists to discuss. The Father depends on the Word and Wisdom He begets to be wise and wordful, but that is only to say that God depends on God.