Is there a conflict between the justification by faith found in Paul's writings and the justification by works found in James?
There are potential problems with any solution to this apparent conflict. One problem for the idea that they are really talking about something different is that we see evidence of a conflict between "justification by faith alone" and observing the law of Moses (ie, "works of the law").
Acts 15:1 Now some men came down from Judea and began to teach the brothers, “Unless you are circumcised according to the custom of Moses, you cannot be saved.” 15:2 When Paul and Barnabas had a major argument and debate with them, the church appointed Paul and Barnabas and some others from among them to go up to meet with the apostles and elders in Jerusalem about this point of disagreement.
The first disagreement was over the specific issue of circumcision of the Gentiles coming to the faith. Paul, of course, said Gentiles didn't have to be circumcised, but other Jewish believes said they did. Secondly, this seems to have rolled over into a broader issue of observing the Law of Moses:
Acts 15:5 But some from the religious party of the Pharisees who had believed stood up and said, “It is necessary to circumcise the Gentiles and to order them to observe the law of Moses.”
The ruling administered from James was that the Gentiles had to follow a few rules, but weren't required to circumcise themselves or observe all of the Law of Moses. But, the problem didn't seem to go away quietly. Paul later goes to Jerusalem again; and again he is confronted about his teachings, but this time about teaching fellow JEWS that they didn't need to be circumcised or follow the Law of Moses.
Acts 21:18 The next day Paul went in with us to see James, and all the elders were there. ..................21:21 They have been informed about you – that you teach all the Jews now living among the Gentiles to abandon Moses, telling them not to circumcise their children or live according to our customs.
James and the elders then come up with a ruling for Paul to take a course of actions to prove that he does live in conformity with the Law of Moses, contrary to the claims of his accusers. But from Paul's own writings, it seems we may know the truth - Paul did in fact teach them they didn't need to be circumcised or observe the Law of Moses.
Gal 2:15 We are Jews by birth and not Gentile sinners, 2:16 yet we know that no one is justified by the works of the law but by the faithfulness of Jesus Christ. And we have come to believe in Christ Jesus, so that we may be justified by the faithfulness of Christ and not by the works of the law, because by the works of the law no one will be justified.
In Galatians for example, Paul opens the letter describing his authority as coming directly from Christ. He emphasized that he didn't even see the apostles for a full 3 years after he was converted (Gal 1:18), after which he only saw Peter. He finally saw James for the first time 15 days after he saw Peter (Gal 1:19). All of this is done to say that he received his authority from Jesus, not Peter, James or any of the other apostles or Jerusalem leadership.
From Acts we know the "other gospel" Paul writes about in Galatians 1. It included stipulations that you had to be circumcised and/or follow the Law of Moses. This is what Paul is writing against. We know from Gal 2 that James is the one who sent people to confront Peter and force him to observe the Law of Moses. It seems we may even know who "slipped in" on Paul with hidden intend to spy on him (Gal 2:4-5) - it seems it may have been Silas and Judas Barsabas (Acts 15:22) since they were with him on his first visit to Galatia (Acts 16:6); and these were the ones sent by James and the Jerusalem leadership to accompany Paul. We see Paul's disdain for the Jerusalem leadership in Gal 2. It's at this point in Gal 2 that Paul says everyone is justified by faith and not works of the Law.
We know the meeting in Jerusalem that Paul refers to in Galatians is the first meeting with James and the apostles since Barnabas was with him (Barnabas separates from Paul after the first Jerusalem council). So we also seem to know that the charges from James in Acts 21 were in fact stemming from what Paul was saying since we have written evidence of it in Galatians.
The conflict between Paul and James appears to have been real, which means the conflict between justification by faith and justification by works was a real conflict that is reflected in the New Testament writings. But the "justification by works" wasn't an abstract moral sort of "works" as in, doing good things, but was in specific works found by observing the Law of Moses and doing the works of the Law. The unconformable conclusion then, if this is true, is that not only does the book of James conflict with Galatians and Romans, but James and Paul were writing to a large degree in opposition to one another!
Of course, it could be the case that Paul and James, though they were writing in opposition to one another, were really misunderstanding one another and talking past each other. It still could be the case that they say the same thing, but mean something more nuanced. Paul's view of justification by faith does, perhaps, seem more nuanced than the credit James was giving him since justification by faith wasn't a license to sin or ignore the purpose of the Law of Moses in the first place. And James' view of works of the Law didn't seem centered on necessity of ritualistic observance, as if you just go through some motions to check a box and meet some requirements, but on intents of the heart, why they were to be done, and their results/outcomes.
