What then can we conclude concerning claims that none of the gospel writers were eyewitnesses to the events that they describe? First, on one level it must be admitted that this position could be correct—none of the gospels bear explicit identification of the author or date of writing— and it bears repeating that none of the writers had to be an eyewitness for the gospel accounts to be authoritative. Second however, it must be remembered that the goal of undermining the historical reliability of the canonical gospels does not necessarily follow from any conclusion concerning the eyewitness status of the events recorded. As modern studies concerning trial testimony has demonstrated, eyewitnesses can be wrong. Each gospel account must stand or fall on its own historical merits.
Third, it must be emphasized that while we cannot be certain that any of the gospel writers were eyewitnesses, there exists evidence that the writers of Matthew, Mark, and John were in fact eyewitnesses of the events that they recorded. Fourth, Luke’s account, while admittedly not an eyewitness account, relies heavily upon early eyewitness accounts, and remains one of the most historically verifiable sources of ancient western literature. Thus, it must be concluded that while claims that the Gospel writers were not eyewitnesses could be correct, it remains unlikely that none of the gospel writers were eyewitnesses to the life, death, and resurrection of the Jesus of Nazareth, and even less likely that the gospel writers were unhistorical in their research and writing methodologies. Such claims thus falls short of critical acceptance, as does the underlying goal of undermining Christian reliance on the historical reliability and veracity of the canonical Gospel accounts.
There is obviously much more that can be written (as has been) on these issues. What resources would you suggest for future study?