"What shall we say, then? Is the law sin? God forbid. But I do not know sin, but by the law; for I had not known concupiscence, if the law did not say: Thou shalt not covet. But sin taking occasion by the commandment, wrought in me all manner of concupiscence. For without the law sin was dead. " - Romans 7:7-8 (Douay-Rheims/Roman Catholic translation)
Works of the Law/N.T. Wright
It has been suggested that I read Bishop Wright's interpretation on justification. I have, it's wrong. This passage proves all the points against him.
He - and subsequently RCs - has interpretted the 'works of the law' which we are not justified by, as 'external legal/mosaic works and ceremonies' (ex. circumcision). His Grace concludes that Christian justification is primarily the life of Christ lived in us and shown by virtue, by following the 'spiritual law' of Christ (his morality). He rejects the claim that the Reformers made that 'works of the law' meant good works performed by Christians.
It shows that covetting - an internal matter of the heart, IS opposed to the law/'works of the law'. Covetting is not a mosaic ritual, it's an issue of Christ-like virtue.
Likewise Galatians 5 lists the gifts of the Holy Spirit and says, "against such things there is no law", again identifying virtue with 'the law'.
The case laid out at the Council of Trent, which I knowingly reject, is the argument that it is not sin formally dwelling in us that St. Paul refers to, but concupiscence (the desire for sin in St. Augustine, or material original sin in Thomas Aquinas - even here you see how the RC shift is made to rethinking humanity's sinful nature). I've already shown how Thomistic hermeneutics obliges us to read "sin" here and in Romans 7:20 as Formal, Substantial, and Entire, SIN.
Likewise in 7:8 "sin taking occasion by the commandment, wrought in me all manner of concupiscence". What is the subject of the sentence: sin. What is it doing? causing concupiscence/lust/the desire for sin. This is totally the opposite of Trent! Trent says that concupiscence - which isn't sin, but dwells in us - leads us to sin. St. Paul says that sin - which IS sin, dwells in us - and makes us have concupiscence/desire for sin.
I don't know how it could be any clearer that while one may not be comfortable with saying "sin nature" (I actually had an FSSP priest use this phrase twice with me by the way in confession - James knows the guy!), the passage clearly implies that Sin is dwelling in Christians, and making them desire sinful things.
This isn't the rose-coloured picture we get of the scholastics, with a good human nature merely having a potential for evil. (I learned my understanding of Thomas' doctrine of Original Sin, by reading the Called To Communion posts on Trent, and Chesterton's book on St. Thomas)