You might throw the Council of Trent, Session VI at him:
**Canon 1.
**If anyone says that man can be justified before God by his own works, whether done by his own natural powers or through the teaching of the law, without divine grace through Jesus Christ, let him be anathema.
(Paraphrase: You can’t
earn initial justification - it’s a gift; this refutes the
Pelagians.)
**Canon 2.
**If anyone says that divine grace through Christ Jesus is given for this only, that man may be able more easily to live justly and to merit eternal life, as if by free will without grace he is able to do both, though with hardship and difficulty, let him be anathema.
(Paraphrase: Grace doesn’t just get you started - it is responsible for the whole process; this refutes the
Semi-Pelagians.)
Code:
**Canon 3.
**If anyone says that without the predisposing inspiration of the Holy Ghost and without His help, man can believe, hope, love or be repentant as he ought, so that the grace of justification may be bestowed upon him, let him be anathema.
(Paraphrase: God’s grace, through the HS, comes to us
before faith - again with the
Semi-Pelagians.)
That should get you past the whole “not of works” argument. After that, I like to give the following analogy to help clarify the Catholic position and contrast it with the Protestant ones:
Let’s say that instead of justification or salvation or sanctification or any of those complex and very precise words (which Catholics and Protestants sometimes define differently), let’s say that instead of calling it “Eternal Life”, we call it “a puppy”. It may sound silly, but hear me out…
How can you make God give you a puppy?
What can you do to make God give you a puppy?
Is there any work that you can perform that forces God to give you a puppy?
OF COURSE NOT! That’s good orthodox Christianity.
If God wants to give you a puppy, that’s His choice - you can’t make God give you
anything by your own works. Here’s the thing, though - God
wants to give you a puppy! All you have to do is say “Yes”.
So great. Now you have a puppy. Now what?
Well…you have to take care of it, silly! You have to feed it and walk it and potty train it - it takes work! If you don’t take care of your puppy, your puppy will die.
Now, God (just like
every parent with their kids) knew going into this deal that you wouldn’t take very good care of the puppy, no matter what you said to the contrary. He knew that you wouldn’t always walk it or feed it daily. Maybe you do a pretty good job of things and
mostly take care of your puppy, and if you do - GREAT! As long as your puppy makes it (even barely), you’re in. Welcome to Heaven!
If not, however, you’re like most of us and have let our puppies die; most times we let our puppies die through neglect, not malice. (This is what Catholics call a “mortal sin”.) It doesn’t really matter which way we kill our puppies, though, because in the end we’re still stuck with a dead puppy.
Here’s where God comes in again - He can restore your puppy to life! That’s part of the really good news! If our puppies die, God can bring them back and give us another chance. (The process for restoring our puppies to life according to the Bible is confession.)
WARNING: Confession involves true contrition, which means we’re
actually sorry for our sins (not just
saying sorry, but actually
meaning it). If we apologize to God and promise to try really hard not to do it again, He’ll raise our puppy for us. He paid that price.
So what do Catholics think about faith and works? You can’t “earn” a puppy, but if you don’t take care of it your puppy will die. If your puppy
does die, God will bring it back to life if you’re
actually sorry and promise to do your best to take care of your puppy in the future. If you die with a puppy, you get to enjoy the eternal puppy-love of God (a million times magnified).
Protestants (by and large) don’t think that you need to keep your puppy living to make it to heaven - just that you would
want to if you were really “saved”, and if your puppy happens to die then it doesn’t really matter because you had a puppy at some point and that’s enough. They (by and large) think that it’s very important to tell God you’re sorry about killing your puppy and would like to get a new one, but most would say that it’s not a strict necessity and wouldn’t keep you out of Heaven if you did not. All that matters is that at one point God gave you a puppy. That’s “faith alone” and “once saved, always saved.”
Hope that helps.
God Bless,
RyanL