The New Perspective on Paul, as put forward by several Protestant theologians (Wright, Sanders, Dunn et al), is the thought that when Paul speaks of justification not being by “works of the law”, he is only speaking of the ceremonial and civil laws, not the moral laws.
What this translates to, is that when Paul says: “one is not justified by works of the law”, he is exclusively speaking of the Jewish aspects of the Mosaic Law. So one cannot be justified through the Mosaic laws. The moral law, however, is still in play. Hence, one is justified by faith in Christ plus cooperation with God’s grace in obedience to the moral law. Works done in grace play into justification, however that may look.
James Dunn explains:
[D]enial that justification is from works of law is, more precisely, a denial that justification depends on circumcision or on observation of the Jewish purity and food taboos. We may justifiably deduce, therefore, that by ‘works of law’ Paul intended his readers to think of particular observances of the law like circumcision and the food laws. (New Perspective on Paul, 191)
In this way, Paul is not doing away with all works, but rather works of the ceremonial and civil type. One is not justified by being a “good Jew”; rather one is justified in the last day by being “in Christ” and cooperating in good works through grace. This means that justification is a process, worked in the now, but finished at the final day in harmony with our works in Christ. Essentially, this conflates justification, and sanctification, making them one action of God and man.
What some may not know, is that this interpretation is not new. In fact, Calvin dealt with this argument in his dialogue with Roman Catholics of his day.
There are two basic arguments that Calvin dealt with in his time: the first was what is commonly known as the New Perspective — that works of the ceremonial and civil law were what Paul was arguing against; not works done in the context of the New Covenant. Another argument he dealt with, was that the works Paul was so set against were works done outside of grace: i.e. before one is regenerated. So, works done in a natural state could not justify; after regeneration, however, one can cooperate with grace and grow in justification after being in Christ. In his Institutes, Calvin denied both stances.
[Catholics] explain “works” as meaning those which men not yet reborn do only according to the letter by the effort of their own free will, apart from Christ’s grace. But they deny that these [works of the law] refer to spiritual works. For, according to them, man is justified by both faith and works provided they are not his own works but the gifts of Christ and the fruit of regeneration. For they say that Paul so spoke for no other reason than to convince the Jews, who were relying upon their own strength, that they were foolish to arrogate righteousness to themselves, since the Spirit of Christ alone bestows it upon us not through any effort arising from our own nature…[They also argue] that the ceremonial works of the law are excluded, not the moral works. (Institutes, 744)
So we can see that this issue of “works” came up long before the New Perspective. How does Calvin respond to this charge? And how to works and salvation relate?
[These theologians] do not observe that in the contrast between the righteousness of the law and of the gospel, which Paul elsewhere introduces, all works are excluded, whatever title may grace them [Gal 3:11-12]. For he teaches that this is the righteousness of the law, that he who has fulfilled what the law commands should obtain salvation; but this is the righteousness of faith, to believe that Christ died and rose again [Rom 10:5, 9]… (ibid, 744)
In other words, in the NT, there is a hard line between faith and works in general. Works in general are said to be one way of justification, while faith is said to be another.
[They argue] that the ceremonial works of the law are excluded, not the moral works… Do they think that the Apostle was raving when he brought forward these passages to prove his opinion? “The man who does these things will live by them” [Gal 3:12], and, “Cursed be every one who does not fulfill all things written in the book of the law” [Gal 3:10]. Unless they have gone mad they will not say that life was promised to keepers of ceremonies. If these passages to be understood of the moral law, there is no doubt that moral works are also excluded from the power of justifying. (ibid, 749)
Calvin puts forward the verse: “cursed by everyone who does not fulfill all things written…”. What he proposes is that “all things” necessarily include the moral tenets of the law. What this means for him, is that works and faith are not and cannot be united together in justification. Justification and sanctification must be separated.
[I]n its proper place,.. the benefits of Christ — sanctification and righteousness — are different. From this it follows that not even spiritual works [works done out of regeneration] come into account when the power of justifying is ascribed to faith… From this it is also evident that we are justified before God solely on the intercession of Christ’s righteousness. This is equivalent to saying that man is not righteous in himself but because the righteousness of Christ is communicated to him by imputation (ibid, 744, 753)
In other words, imputation of righteousness and regeneration or sanctification are distinguished, separated. Sanctification is something that flows from imputation, but is not the same thing. New Perspective (and Romans Catholics) place together the work of justification and sanctification, such that one can participate in his final justification through works done in grace.