Thank you BrotherAlan for correcting me concerning my misapprension that the Roman Catholic Church believes in ongoing revelation. I hereby accept your explanation that it does not. It merely claims to have the authority to interpret correctly what has already been revealed.
You wrote:(since "begotten before all ages" could leave open the possibility that the Son is not eternal, but was simply created before the rest of creation, which is contrary to Trinitarian Faith).
That is correct. Indeed Arius did hold that belief, since in his letter to Eusebias, he wrote that before the Son was begotten, He did not exist.
However, I believe that "begotten before all ages" DOES imply that He was begotten (or "generated")as a single act of the Father, rather than a continuous "eternal" begetting (whatever that means) If that single act marked the beginning of time, then there was not a previous time at which the Son did not exist, since there was no "before".
Being begotten as a single act does NOT imply creation. You and I have been begotten through our parents, but they didn't create us. An artist creates a painting, but that painting differs essentially from the artist. You and I do not differ essentially from our parents. We are human as they are. The Son did not differ essentially from His Father. He is divine as His Father is.
Justin Martyr (110-165 A.D.) understood the begetting of the Son as a single act. In his dialogue with Trypho and his companions, Justin stated:
“I shall give you another testimony, my friends,” said I, “from the Scriptures, that God begat before all creatures a Beginning, a certain rational power from Himself, who is called by the Holy Spirit, now the Glory of the Lord, now the Son, again Wisdom, again an Angel, then God, and then Lord and Logos; and on another occasion He calls Himself Captain, when He appeared in human form to Joshua the son of Nave(Nun). For He can be called by all those names, since He ministers to the Father’s will, and since He was begotten of the Father by an act of will; ... just as we see also happening in the case of a fire, which is not lessened when it has kindled [another], but remains the same; and that which has been kindled by it likewise appears to exist by itself, not diminishing that from which it was kindled. The Word of Wisdom, who is Himself this God begotten of the Father of all things, and Word, and Wisdom, and Power, and the Glory of the Begetter, will bear evidence to me, when He speaks by Solomon the following: ‘If Ishall declare to you what happens daily, I shall call to mind events from everlasting, and review them. The Lord made me the beginning of His ways for His works. From of old, He established me in the beginning, before He had made the earth, and before He had made the deeps, before the springs of the waters had issued forth, before the mountains had been established. Before all the hills He begat me. God made the country, and the desert, and the highest inhabited places under the sky. When He made ready the heavens, I was along with Him, and when He set up His throne on the winds: when He made the high clouds strong, and the springs of the deep safe, when He made the foundations of the earth, I was with Him arranging..." (from Dialogue with Trypho, ch LXI)
So it seems clear that Justin regarded the begetting or generation of the Son as a single act, and not an ongoing process (which "eternal begetting" seems to suggest).
Oh, by the way, Brother Alan, are you a monk? I am not aware of Catholics calling any of their people "Brother so-and-so" except he be a monk, or "Sister so-and-so" except she be a nun.