God, not the Son as such, reveals himself in theophanies
Augustine's View on Old Testament Theophanies
Augustine and Vidu have made me re-think the notion that the Son is the Person usually revealed in Old Testament theophanies. If we say this, it makes it sound as if the Son is visible unlike the Father and Spirit who are invisible (1 Tim 6:16).
I now think that God generally reveals himself in OT theophanies by a created form (fire in the bush, angel of the Lord, a thunderous voice, etc.).
Theophanies Reveal God
Some theophanies by appropriation may better fit one Person, I suppose. But generally, the one God—Father, Son, and Spirit—reveals himself in the burning bush, and who names himself as "I AM." "I AM" is the one God of Israel—Father, Son, and Spirit.
Augustine particularly convinces me of this argument as it's easy to think that the Son would pre-reveal himself in the OT because he alone as a Person incarnates. But God is Spirit, and no one has seen God. We see Christ and thus see the Father in a unique way in the Incarnation.
To see the Son is to see the Father in the face of Christ. But if God by nature is invisible (1 Tim 1:17), then the Son and Spirit must too be invisible by nature or we have three gods. But we have one God (Deut 6:4).
Therefore, it's inappropriate to say that the Son by nature is more likely to be visible in OT theophanies. The Incarnation is a unique event. It's fitting due to relations of origin, not because the Son is more visible than the invisible Father.
Augustine's Theological Context
Why does Augustine believe that OT theophanies are created effects of the one God, not a revelation of the Son in particular? To answer that question, we need to look at his anti-Arian theological context.
Although scholars like Vidu and Michel Barnes clarify Augustine's anti-Arian context in De Trinitate, I also think Augustine makes it clear in his debate with Maximinus as to why he takes theophanies to be of God, not the Son in particular.
In his debate with Maximinus (an Arian Bishop), Maximinus argues strongly that the only-begotten God cannot have the same nature as the one God, the Father, because the Son was made visible in the OT through theophanies, and the one God is invisible (e.g., 1 Tim 1:17).
This likely explains why in De Trinitate Book II-IV Augustine spends so much time on theophanies. He wants to show that theophanies of God in the OT are of God under the form of a created effect, and not the Son Himself in a pre-Incarnate revelation of Himself.
Were that true, it would both suggest that the Son is by nature visible (so not the one God who by nature is invisible and whom nobody has ever seen) and that the Incarnation is a sort of progressive event. Both can't be true, since the Son is the one God of Israel made flesh in time.
However, this position does not mean a theophany cannot by appropriation say something of one Person. Maybe Jesus's Baptism would illustrate the point, I am not sure yet.
Conclusion
For now, I find myself persuaded by Augustine. Theophanies reveal God.
