Didn’t think you were very familiar with Aquinas, just pointing out that what you were saying is the “Thomist” position as well.
Aquinas used Aristotle’s approach to the term “cause”, which is different from the way that term is typically used in Byzantine theology. For Aquinas, from Aristotle, everything that can in any way be said to participate in the existence of something is a cause of it. So God is my cause, my parents are my cause, carbon and H20 are my cause, love and a twinkle in my mother’s eye are my cause, ect. My First Cause, however, is God and God alone; everything else is a secondary cause, and the term Source is really only applicable to the First Cause because every other cause follows from the First Cause. Another important point to remember is that “First Cause” doesn’t imply any kind of sequence in time or steps, but rather it means that every other cause is caused by this one cause. Hence the relevance of the spring-river-lake analogy.
The fact that Aquinas was the Latin Doctor that “translated” Eastern theology into the Latin tradition is often overlooked, or not even realized, in these discussions. There’s good reason that his position is the same as St. Gregory’s, though he was expressing it in “Latinese”.
The Summa Theologica is basically the “Exact Exposition of the Orthodox Faith”, by St. John of Damascus, put into a point-counterpoint format.
Peace and God bless!