What does Acts 15:6 mean?

Paul, Barnabas, and others from the mostly Gentile church in Syrian Antioch have come to the church in Jerusalem. They seek a formal decision on whether Gentiles must be circumcised and follow the Mosaic law. That is, do people need to convert to Judaism to follow the Jewish Messiah (Acts 15:1–5). They know the answer is "no," but they do not have the executive authority of the apostles and James, the half-brother of Jesus.

We owe much to the early church leaders for being willing to fight through these theological issues. When Jews followed Jesus, they faced a massive shift in their worldview. While truth had not changed, their perceptions of it were drastically altered. Sacrifices did not save; parts of the Mosaic law, like the Sabbath and feasts, held less relevance than before; and Gentiles, once considered unclean pagans, became brothers and sisters in Christ.

Instead of acting imperiously, demanding Gentiles accommodate their cultural norms, the Jewish church leadership gathers together. They fully debate the issue, refer to Scripture, consider physical evidence, and ask the Holy Spirit (Acts 15:7–21, 28). This method of defining theology continues throughout early church history as more questions arise: the deity vs. humanity of Christ, the essence of the Trinity, the Person of the Holy Spirit, and many others. The debates continue in Christianity, with less universal agreement, on issues such as the sufficiency and integrity of Scripture, the existence of an eternal hell, and—still—the essence of the Trinity.

The "apostles" mentioned here are believed to be the ten remaining disciples of Jesus (James had been martyred; Acts 12:2) plus Matthias, who replaced Judas (Acts 1:26). The elders are presumably lay leaders of the church in Jerusalem. They would be Jews who had been taught directly by the apostles, or, possibly, by Jesus before His ascension.