I can’t resist! I won’t make this long, but I will say a few things:
The Reformers doctrine of Justification by Faith Alone may be the starting grounds in some way of the “Eternal Security” opinion, or the “Carnal Christian” Heresy, but I’m not convinced that can be proven. “Once saved always saved” can be interpreted to mean something very glorious, with a proper understanding of the Calvinist Doctrine of Limited Atonement and Perseverance of the Saints.
I take it you are thoroughly knowledgeable with the “5 Points” of Calvinism and the grounds for believing Sola Fide, so I won’t give the standard arguments. But rather I will say, for someone who believes it, Trent’s anathemas will do nothing to phase their beliefs.
However, here are a few quotes from Church Fathers that you may find interesting:
Epistle of Clement to the Corinthians
32:3 So all of them received honor and greatness, not through themselves or their own deeds or the right things they did, but through His will. And we, therefore, who by His will have been called in Jesus Christ, are not justified of ourselves or by our wisdom or insight or religious devotion or the holy deeds we have done from the heart, but by that faith by which almighty God has justified all men from the very beginning.
Justin Martyr’s 1st Apology, Dialogue w/ Trypho
Abraham, indeed, was considered just, not by reason of his circumcision, but because of his faith. For before his circumcision it was said of him: Genesis 15:6
Irenaeus, Against Heresies, Book 4, Ch. 5, Sect. 5
The Lord, therefore, was not unknown to Abraham, whose day he desired to see;nor, again, was the Lord’s Father, for he had learned from the Word of the Lord, and believed Him; wherefore it was accounted to him by the Lord for righteousness. For faith towards God justifies a man; and therefore he said, “I will stretch forth my hand to the most high God, who made the heaven and the earth.” All these truths, however, do those holding perverse opinions endeavour to overthrow, because of one passage, which they certainly do not understand correctly.
Same, Chapter 9, Sect. 1
For the Lord is the good man of the house, who rules the entire house of His Father; and who delivers a law suited both for slaves and those who are as yet undisciplined; and gives fitting precepts to those that are free, and have been justified by faith, as well as throws His own inheritance open to those that are sons
And Scripturally, I would ask you this question that plagues me about the Catholic view of Justification:
Romans 4:9-11
Is this blessing then upon the circumcised, or upon the uncircumcised also? For we say, “Faith was reckoned to Abraham as righteousness.” How then was it reckoned? While he was circumcised, or uncircumcised? Not while circumcised, but while uncircumcised; and he received the sign or the faith which he had while uncircumcised, that he might be the father of all those who believe without being circumcised…"
How could Abraham be righteous before he was circumcised, since circumcision is the OT type of Baptism. I say that he was righteous in the eyes of God (Justified) by his faith alone, before he did any works commanded by God in His Law, yea even before the command came! Circumcision was introduced in the Covenant given in Genesis 18! And Abraham obeyed, and that’s proof of his faith, that it is a true faith, as James speaks of, a living faith not a dead faith.