@MW Thank you for your answer. I have to spend some time to chew the cud. There is another question which is outside of this post, i.e concerning the teaching of Karl Barth and Karl Rahner on the Immanent Trinity and Economic Trinity, I believe they taught the economic Trinity is the immanent Trinity and vice versa? I believe they did so to bridge the distinction ("gap") between the Ontological Trinity and the Economic Trinity (
https://thirdmill.org/answers/answer.asp/file/44529). It seems to have been imbibed by many reformed people. Is there a problem of this view of the two Karls? Thank you.
In classical theology the immanent is what God is eternally in Himself; the economic is what God is towards us in creation and redemption. The doctrine of the Creator-creature distance and of divine accommodation necessitates this distinction. In Trinitarian discussion the language was so ingrained that it gave the impression there are two Trinities. Rahner's rule was an over-correction which was intended to resolve this unnecessary use of language. We should not think we are speaking about two actually different things.
Rahner and Barth were concerned by the impression that there was a "hidden God" behind revelation, One who is different in Himself than He is towards us. For Rahner this left a gap between God's eternal life and His saving work. So he proposed the economic Trinity is the immanent Trinity, and the immanent Trinity is the economic Trinity. But this does not clarify anything. It collapses the conceptual distinction which makes "theology" possible in the first place. Without an accommodated revelation God is too high for us to understand. His greatness none can comprehend.
At its heart the Rahner rule makes two things identical that must remain distinct -- the Father eternally begetting the Son and the Son incarnate. Classical theology teaches that the missions reveal the processions, but they do not constitute them. Rahner's Rule makes them identical. That is the over‑correction. And it creates a whole range of new problems.
The solution, which avoids both errors, is to say the economic Trinity truly reveals the immanent Trinity, but it does not exhaust it. God is toward us as He is in Himself. This is in Christ, the God-man, who Himself constitutes a mystery we cannot comprehend. He is God with us. Yet God's own immanent and eternal life is not dependent on His works in time.
Treier at thirdmill is correct on two points: The economic Trinity truly reveals the immanent Trinity. God's works manifest who He is. There is no "false God" in revelation. Likewise, God reveals Himself freely. Creation and redemption are free acts of God, not necessary emanations. These two points are orthodox.
But Treier introduces another concept when he says the economic Trinity "corresponds" to the ontological Trinity. A quiet shift has happened at that point. There is no gap. The only caveat allowed is divine freedom. This would mean God's eternal identity includes His historical acts and God's being is partly constituted by His relation to creation. This undermines divine aseity and simplicity.
However, the thirdmill "answer" is so brief that it could be taken to mean any number of things. It is simply incomplete and insufficient as an answer.