HEREVER God does something great, men are sure to try to regulate it. Such was the case with the salvation of the gentiles. Great progress was being made, but a distraction came along to slow things down a bit. In Antioch of Syria, there were teachers who came in teaching that the physical rite of circumcision was necessary for salvation. It's like teaching that baptism is necessary for salvation, or that law-keeping is needed for salvation. It simply isn't true. Paul and Barnabas fought this heresy hard and loud, but the dispute was sharp enough that the church sent these two missionaries down to Jerusalem to get an official word from the apostles on this debate (Acts 15:2). There is no reason to wonder whether Paul and Barnabas knew what the answer would be or not. They knew God was working among the gentiles without circumcision, without the law, and without interference. In fact, on their way to Jerusalem, Paul and Barnabas continued to spread the good news of God's grace to the uncircumcised (Acts 15:3). They weren't exactly unbiased researchers, but their bias was on the side of the truth.
So, the church in Jerusalem convened their first council/convention. They came together to formulate an official statement to send to new gentile believers. In this meeting, Peter reminded the church leaders of his experience with Cornelius. Peter's perspective was boldly gracious & true (Acts 1:10). Paul & Barnabas spoke in defense of the gentiles as well. Then James spoke. He seemed to be the final voice on this matter. As he quoted appropriately & powerfully from the Old Testament, the issue was settled.