Love this quick yet effective refutation of sola fide (which the Protestants didn't see coming).

I think I've come upon a devastating yet subtle 'quickie' argument against the Protestant (especially Reformed) notion of justification by faith alone. Catholics will often point out that "faith that works through love" is what Paul meant when he spoke of the essence of a justified believer (Gal 5:6), and that without love we are told by James that "faith is dead" (James 2:24-26). Protestants think they have an answer for this, by insisting (without proof) that "true faith always comes with love" with it. This seems like a save at first, but thinking about this means the Protestant is saying that when a person receives the gift of faith prior to justification, they also receive the gift of love along with it. That's a problem, and here's why. 

If a person receives faith and love prior to justification, it means the unsaved individual loves God already, prior to even accepting the Gospel message! This cannot be, and thus the Protestant must reject this and say faith doesn't automatically include love along with it prior to justification. This leads to a few significant but plain conclusions:

(1) Faith prior to justification lacks love, and thus this faith must start off 'dead'. This isn't necessarily a bad thing, just an incomplete thing, which is why justification is still needed. 

(2) Justification must be what bestows love, and this seems confirmed by Scripture (e.g. Romans 5:5), and thus the Protestant can no longer say justification is purely forensic, but rather infuses divine gifts into the soul.

(3) Dead faith prior to justification becomes living faith after justification by the addition of love to faith, and herein is the essence of a justified believer. This would mean it isn't Christ's Imputed Righteousness that makes all the difference, but rather the presence/absence of love, and thus suggests your justification (salvation) hinges upon what you do with that love. This is why texts like Revelation 21:8 list "unbelief" as one of the many sins that can damn a person, because it's possible to have faith and be damned by other grave sins.

Given the above, when Paul says we are "justified by faith," he isn't saying we are "eternally saved by faith," rather he's saying that we receive God's love within us by believing in the Gospel, and that this is just the beginning of our salvation (Rom 13:8-14; Gal 5:13-14).

How Protestants completely botch the Biblical teaching on what being "Born Again" means (a.k.a "Regeneration" in Calvinism)

As I looked upon the Catholic Encyclopedia entry on "Regeneration," I was fascinated by what I saw. Below I will quote from the entry, but trim it down for brevity and to highlight some key points:

Regeneration is a Biblico-dogmatic term closely connected with the ideas of justification, Divine sonship, and the deification of the soul through grace. Confining ourselves first to the Biblical use of this term, we find regeneration from God used in indissoluble connection with baptism, which St. Paul expressly calls "the laver of regeneration" (Titus 3:5). In His discourse with Nicodemus (John 3:5), the Saviour declares: "Unless a man be born again of water and the Holy Ghost, he cannot enter into the kingdom of God." The idea of "birth from God" enjoys a special favor in the Joannine theology. Outside the Fourth Gospel (Jn 1:12 sq.; 3:5), the Apostle uses the term in a variety of ways, treating "birth of God" as synonymous now with the "doing of justice" (1 John 5:1, 4 sq.), and elsewhere deducing from it a certain "sinlessness" of the just (1 John 3:9; 5:18), which, however, does not necessarily exclude from the state of justification the possibility of sinning. It is true that in all these passages there is no reference to baptism nor is there any reference to a real "regeneration"; nevertheless, "generation from God", like baptismal "regeneration", must be referred to justification as its cause. Both terms effectually refute the Protestant notion that there is in justification not a true annihilation, but merely a covering up of the sins which still continue (covering-up theory), or that the holiness won is simply the imputation of the external holiness of God or Christ (imputation theory).