I was told by Kolokotronis that Augustine did not understand Trinity because he did not know Greek. He did not provide any criticism of Augustine's reasoning beyond that he did not refer to any Greek words. I am hoping to get more from Kolokotronis today.
I'm a bit mystified a to why Augustine is figuring prominently on this thread. Is someone explaining the rise of the Filioque as the result of Augustine's trinitarian theology? Or is it just because Augustine was influential in the West? But so too was Hilary . . .
The Filioque arose from an effort to counter Adoptionism in Spain long after Augustine. No creed at all was recited in the Mass at Rome for centuries. It was the Carolingians, in their effort to show that the Byzantines were illegitimate emperors and that the Carolingians had preserved the true Roman imperium, pressured the popes to add the Nicene Creed with the Mozarabic filioque to the Roman liturgy. For a long time the popes resisted but finally added it, as late as the 11thc, if I am not mistaken. The "because he did not know Greek" is an old canard thrown at Augustine. The Greek struggle over hypostasis and prosopon in the late 300s and 400s could equally be attributed to the fact that they did not know Latin and thus Tertullian's brilliant adding of Christian meaning to what had in Graeco-Roman culture been a rather blank (mask, role in Greek drama, prosopon, persona), empty, impersonal term. It's not simply a matter of knowing or not knowing language.
A very good but little-known effort to reconcile Eastern and Western views on the procession of the Holy Spirit by employing the Hebrew/Greek chabod/doxa as expounded in the Farewell Discourses, particularly Jn 17, is found in Paul M. Quay, S.J., The Mystery Hidden for Ages in God (New York etc.: Peter Lang, 1995), in the first part of the book. He also offers a profound effort to reconcile East and West on original sin, taking account even of what we now know about fetal psychology and the plasticity of the brain as it develops (Quay had a PhD in physics from MIT but also did part of his theological training under De Lubac at Lyons. His book is an effort to apply the patristic spiritual sense of Scripture to the development and growth of spiritual life, first in the OT as we (the Jewish people) crawled back from the horrible abyss of alienation from God produced by the Fall to even be ready for the Incarnation, then, after the Incarnation, the growth in holiness in the Spirit toward theosis, all of it done typologically in accord with the patristic method. It's well worth reading, slowly, ruminatively.
As for Blessed Augustine, his translations show that he did not understand Greek and that he incorrectly interpreted Greek sources -- one particualr stands out, regarding Genesis, confusing the word "in common" with "instantly."
Likewise, the concept of procession from a source, versus sending in time, for which Greek has two distinct terms and Latin just one (procedere) for both is a source of erroneous conceptualization of the Trinity. God is one, Triune, interrelated, of one essence or nature, with all three Hypostases equally divine, yet separate Personae, the revealed energies, co-substantial, in perfect harmony. Triune God reveals the monarchy of the Wisdom, which generates the Word, and the Spirit that proceeds from the Wisdom. The Divine Economy leaves no doubt that being co-substantial is not a two-way or a three-way street, but that the Wisdom begets the Word, and not the other way around, and that the Father, Who is the source of everything and all, and not the Son, is the source of the Spirit and not the Spirit of the Father or of the Son. Yet at no time is one less Divine than the other -- these energies reveal a Divine Being we call God, just as our mind and words are, and our spirit that is sent through the words, but does not originate in them, reveals a person that we are; made in His image and likeness.