Obviously, we cannot know who the men from James really were, but in another blog I wrote some time ago I argue that they were probably very notable men, perhaps powerful Jews who worshiped with the brethren at Jerusalem. It is unlikely that either Peter or Barnabas would have been seduced doctrinally. That may have been a problem at Galatia with the new believers, as well as the new gentile believers at Antioch, but Peter and Barnabas were teachers of the word of God. Their seduction came by way of pleasing men. In other words, they were intimidated in the presence of men from James. They changed their behavior, not their doctrinal understanding. They acted hypocritically, that is, not according to what they knew to be correct.
In Galatians 2:15 Paul says “We who are Jews by nature and not sinners of the gentiles”! What does he mean? Paul was probably addressing an argument put forward by the men from James – **we** i.e. Paul and Peter are indeed Jews by nature and not sinners derived from the nations (gentiles). On its face the argument breeds division, but Paul uses it to develop his own argument against behaving in a divisive manner, such as Peter showed himself doing. Paul showed that the very Law in which the Jews trust cannot justify sinners before God (Galatians 2:16). Therefore, if the very Law that would separate Jew and gentile cannot make the Jewish believers any more righteous before God than gentile believers, what is the purpose of separating Jewish and gentile believers in worship?
Both Jew and gentile are justified by faith (Galatians 2:16) not by the works of the Law. By its very nature the Law keeps us from that which we seek. All have sinned (Romans 3:23), and when we sin we create a division between us and God. Our sins hide his face from us (Isaiah 59:2). The Law, in which so many of us trust, divides sinners from God, Jews from gentiles, and the living from the dead (cp. Romans 5:12). The Law demands our lives, because the wages of sin is death—our lives are what we owe the Law, and death is what we earn by sinning (Romans 6:23a). Eternal life is God’s gift to us, which we receive not through obedience to the Law but through Jesus (Romans 6:23b). Paul’s argument is that death, not life, comes through the Law. Therefore, believers should not permit the Law to separate brethren. Having, knowing and practicing the Jewish Law does not make a Jew any better than a gentile who is obeying the law of his own land (Romans 2:14-15). It makes no sense, therefore, for Jewish and gentile believers to eat and worship in separate areas. To do so is hypocritical.
Peter’s theology was in complete agreement with that of Paul (Acts 15:7-11). He may have been drawn away by the men from James, because he was intimidated with their presence, but, when he was brought to his senses through Paul’s rebuke, he publicly admitted that neither the fathers who were before them nor those of the of the 1st century AD were able to keep the Law. Therefore, **all** are sinners—whether Jew or gentile—and the Law cannot change that, because, although it is able to show us what sin is, it is powerless to make anyone righteous. Therefore, Paul’s point is made that brethren should not separate themselves over one’s personal religious traditions.
 On December 5, 2012 I wrote a blog entitled The ‘Men from James’ where I argue that these men were probably wealthy, powerful Jews from Jerusalem. They were probably false brethren of the caliber of Ananias and Sapphira (Acts 5:1-10), who came into the believing community in order to bring believers under their power and waited for an opportune time to make their move (cp. Acts 5:13).