What does Acts 6:8 mean?

We don't know a lot about Stephen; Scripture does not mention him beyond the context of his story in Acts 6—7. He is a Hellenist Jewish-Christian, meaning he is Jewish, but is not from Jerusalem; he was raised elsewhere in the Roman Empire where the primary language was Greek instead of Aramaic. He is "of good repute, full of the Spirit and of wisdom" (Acts 6:3) and other church members choose him to be one of the first deacons (Acts 6:5). However long he has been a Jesus-follower, he has used his time to good effect; other Hellenist Jews cannot match his wisdom, in large part because he is so submissive to the Holy Spirit (Acts 6:10).

"Wonder" is from the Greek root word teras, and "signs" is from the root word semeion. A wonder is a miracle that reveals a hidden truth, while a sign identifies the miracle-worker as God's messenger. We don't know why the men Stephen is debating refuse to accept the authority represented in the miracles he performs. The reason they give is that Stephen wants to see the temple destroyed. Stephen will succinctly explain why this is a non-issue with a quick recitation of Israel's history (Acts 7:1–50).

The God-endowed protection that God has given the early church in Jerusalem is eroding. The Jewish leadership has arrested and beaten the apostles (Acts 5:17–42). Jesus trained the apostles to expect persecution (John 15:18–20), and it's reasonable to assume the apostles passed on this warning to the new Christians. God knows Stephen's opponents will grow into a mob that will kill him (Acts 7:54–60), but He will effectively use Stephen's sacrifice. The coming persecution will spread Jesus' followers and His gospel message all over the known world.