What does 1 Corinthians 15:7 mean?

To believe in the physical, bodily resurrection of Jesus from the dead has never required blind—"evidence-free"—faith. When Paul wrote these words in the first century, evidence of Christ's resurrection was even easier to encounter. Yes, it is necessary to believe in the resurrection of Jesus in order to believe the entire gospel and be saved. The difference between now and then was that those who really wanted to know about the resurrection could interview those who saw Jesus alive again with their own eyes. The people of the early Christian church had access to those who walked and talked with Jesus both before and after His death on the cross.

Paul is building a list of who that includes. He has added Peter, the other disciples, another 500 people, most of whom were still living. He then includes James, Jesus' half-brother, and the rest of the apostles. Since Paul already mentioned the 12 disciples, later known as apostles, the "apostles" he references here must have described another group of leaders in the early church.

That's a lot of people who saw Jesus alive after He was dead and buried.