Some skeptics suggest that we do not have accurate sources in the Gospels because they were written too late (often assumed to be 40-50 years after the crucifixion). This claim makes some major assumptions. It assumes that no one was passing on the traditions in any reliable way before they were written down. It is as if the evangelists sat down a generation after the events, tried to remember what they could and filled in the rest with their imagination.
This is not an accurate picture by many means. I really appreciate what James Dunn says about the nature of an oral society in his essay in The Historical Jesus: Five Views.
We think in a box of literary dependency, of copying and editing. And we are the more confident of the results of our analysis of that tradition because they are so containable within the box. But the box is one construed by the fifteenth-century invention of printing, and it prevents us from seeing outside of its containment. We shut out the reality of what an oral society must have been like, and have failed to think through the character of the traditioning process in an oral society. We think that the results of reconceptionalizing the process of oral transmission would be destructive of our grasp of the tradition’s “authenticity” because of orality’s inherent stability. And the outcome is that we cut ourselves off from the Jesus we want to discover and hear again afresh in his own terms. (p. 210)