At the heart of the doctrine of imputation [Protestant view] is a belief that salvation is legalistic – it can only be achieved by perfect obedience to God’s law. Since we can’t perfectly obey the law due to sin, Christ obeys it in our place, “as if I myself had accomplished all the obedience which Christ has rendered for me” (Heidelberg Catechism QA 60). The assumption is that man is saved by obedience to the law; but since our own obedience is polluted by sin, we need Christ’s obedience to be saved.
When it comes, then, to the question of God’s glory, the Reformed person understands that glory in terms of this legalistic framework. Since obedience to the law is what saves us, and since Christ obeyed the law perfectly in my place, to speak of my own good works as influencing my salvation necessarily obscures Christ’s perfect obedience.
But as you pointed out, that whole legal framework is precisely the thing Paul is rejecting. Reformed people often use the book of Galatians against Catholic teaching, and yet it is Catholic teaching that makes perfect sense of the entire letter. In that letter, Paul rejects the law as a means to salvation, and he does so categorically. That is, he’s not contrasting our imperfect obedience to the law with Christ’s perfect obedience to the law, and telling us to seek the latter through faith. He says that obedience to the law in itself is utterly powerless to save:
If a law had been given that could give life, then righteousness would indeed be by the law” (Ga.3:21)
So, even if you could present God with a record of perfect obedience to the law, you would be no closer to having life or righteousness than someone who’d disobeyed the law all his life. That’s because life and righteousness do not come through the law.
We don’t, then, glorify God by claiming that our life and righteousness rest entirely on Christ’s perfect obedience to the law. In fact, we rob Him of glory, for we commit the same error the Galatians were committing by assuming that salvation is legalistic.
No, we glorify God by saying, with Paul, “It is no longer I who live but Christ who lives in me” (Ga.2:20). Joey brought up Ephesians 2:8-9:
For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast.
When Paul speaks of being saved by grace through faith, he’s not speaking about Christ perfectly obeying the law in our place. He’s speaking of the fact that although we were once dead, God has “made us alive together with Christ” (Ep.2:5). It’s this new life that is not a result of works, which is precisely what the Council of Trent taught. God does not make us alive because we first achieve a black belt in holiness. We don’t come to God with a bag full of good works and say, “Here, God. Look at all these good things I’ve done. I now deserve that new life you’ve promised.”
No, we receive it the same way the hemorrhaging woman received healing (Mk.5:25-34). We come to Christ in faith, reach out and touch Him sacramentally, and He in turn pours out His life into our hearts. That woman had no grounds to boast, and neither do Catholics.
When Catholics speak of the glory of God, we aren’t thinking in terms of obedience to the law; we are thinking in terms of the life-giving power of Jesus Christ. The glory of that woman’s health lay in the generous and unstoppable power of Christ. And the glory of our health – a life of good works, a life of communion with others, a life of cooperating with God in prayer and self-denial – lies entirely in that same generous, unstoppable, and life-giving power.
That, too, is what Paul claims removes any grounds for boasting. What removes our grounds for boasting not that Christ perfectly obeyed God in our place. It’s that God has made us alive together with Christ by grace. And that is precisely what the Catholic doctrine of salvation is all about – that new, grace-given life with God.