Virtually all scholars studying Jesus' resurrection, whether conservative, moderate, or liberal, acknowledge that Jesus' earliest followers were convinced not only that Jesus was raised from the dead but also that He had appeared alive to many of them on several occasions. Further, scholars also almost unanimously recognize that two former skeptics, James the brother of Jesus and Saul of Tarsus (Paul), became believers after they, too, were convinced that they had seen the risen Jesus.
Multiple grounds support this early Christian conviction. Even today's most critical scholars agree that Paul, the author of undisputed NT letters, provided eyewitness testimony to Jesus' resurrection appearance. Further, Paul included a crucial report concerning other appearances of Jesus in the exceptionally early creed in 1 Co 15, which is usually dated to the A.D. 30s. Paul carefully checked out this material with other key apostles in Jerusalem on at least two occasions (Gal 1:18-2:10). Paul also knew that the other apostles were preaching the same message regarding the risen Jesus (1-Co 15:10-15). Paul's eyewitnesss testimony at each of these points is crucial.
Moreover, the conversion of James from skepticism, the willingness of the earliest disciples to suffer persecution and even martyrdom, the empty tomb, and the presence of other early reports of Jesus' resurrection especially in Acts are further indications of the apostolic conviction that Jesus had been raised. In brief, the earliest Christian message was that Jesus had appeared to His followers after His death.
Of the many evidences for the resurrection, the most significant is that the earliest disciples were utterly convinced they had seen the risen Jesus. The reason is straightforward. Virtually every contemporary scholar recognizes the strong data showing that Jesus died by crucifixion. So if a number of persons (both individuals and groups) actually saw Him afterward, this would constitute the clearest indication that He had been raised. No other evidence provides such a direct indication of this event. This is clearly what the witnesses proclaimed.
Some critics may counter that, while the early disciples truly thought Jesus had been raised, a natural hypothesis explains their beliefs.
However, now the questioner has a major dilemma. Natural theories have been proposed for centuries and each fails by a large margin to explain the recognized historical data. Incredibly, most contemporary scholars even recognize this failure, Few critics even propose alternative hypotheses!
The earliest disciples clearly taught that they saw the risen Jesus, for which then are plenty of supporting details. What happens when these facts are not naturally explained, as even the majority of contemporary critical scholars admit? The resurrection of Jesus becomes the best explanation of the known data.
All the evidence favors the view that the disciples actually saw the risen Jesus There is no viable evidence to the contrary. So we are left with a succinct conclusion When the many reasons supporting the conviction that Jesus actually appeared to the early Christians are combined with the failure of naturalistic alternative theses, we are justified in concluding that Jesus was actually raised from the dead.
Extracted from the Apologetics Study Bible.