The second question Wilkins and Moreland ask in Jesus Under Fire is “Are the Biblical Sources About Jesus Accurate?” To answer this question we might need to talk a little bit about manuscripts and the copying process, but what is really at stake here is the intention of the original authors. Were they interested in writing an accurate history of Jesus? Everyone accepts the fact that the gospels are theological documents, but that something is a “theological document” does not mean that it is historically inaccurate.
When Historical Jesus scholars approach this question, they usually construct several tests for any given saying or event in the Gospels in order to determine the likelihood that the story really happened. For example, the Jesus Seminar uses several criteria of authenticity to dismisses much of the gospels as inaccurate, fanciful, or at best, a reflection of what might have happened to the real Historical Jesus. There is an assumed distinction between the “Jesus of History” and the “Christ of Faith.” The Jesus of History is virtually unknown, all we really know about is what the faithful believers who wrote the New Testament said about him One only needs to know the Christ of Faith for salvation, but that does not mean that he has to believe in the Jesus of History quite the way the Bible presents him.
A serious problem with these criteria is that they are only employed to support the scholar’s preconceived opinion. In most cases, a particular criterion could be used to prove or disprove a particular event or saying is an accurate reflection of Jesus. One example is the saying in Mark 10:45, which appears in a number of “layers of tradition.” The saying is not quite what we would expect from a Jewish perspective (“Messiah as a ransom” is not a common view in the Second Temple period). Nor is it particularly what the early church might have created to put in Jesus mouth (a “ransom” is not a pervasive metaphor for salvation in other NT documents). Yet the saying is rejected by the Jesus Seminar since it is too theological for their Jesus to say.
Is it likely that the biblical writers passed along information accurately, or were they inclined to “make things up” in order to present Jesus in a better light? Based on documents that are clearly later “fanciful” creations of Christians (such as the Infancy Gospel of James), the Gospels are sober-minded and historical treatments of the events of Jesus’ life. Unless one is inclined to some sort of conspiracy theory, Luke’s claim to be writing an ““accurate account” of the life of Jesus seems to mean that he thought his story was “what happened.”
I suppose that someone could say this is a circular argument since Jesus does miracles which could be described as “fanciful.” But the miracles found in the gospels are all signs of the messianic age drawn from the Hebrew Bible. That the Messiah would heal the sick and even raise the dead makes perfect sense after reading Isaiah 61 or Ezekiel 37. Even the Feeding of the 5000 (a miracle recorded in all four gospels) is an allusion to Israel’s wilderness experience. Jesus declares he is the good shepherd who provides food for true Israel in the wilderness. The reason for the miracles is drawn from the Hebrew Bible, not Greco-Roman myth. Jesus would look quite different if Luke (or anyone) were trying to write the Jesus story to imply “Jesus is like Apollo.”
I find many of the miracles in the post-biblical Gospels less grounded in the Hebrew Bible, reflecting a later, Greco-Roman sense of the miraculous. To me, that is a hint they were created by later writers and ought to be deemed as legend. In contrast, the miracles of Jesus are the sorts of things one would have expected from the Messiah after reading the Hebrew Bible.
Obviously there is more to this, but I think that the writers of the New Testament Gospels were interested in telling the story of Jesus accurately, but they were also interested in explaining what happened theologically. The combination of those two ideas are what bothers some scholars. A “theological document” does not necessarily mean a “historically inaccurate document.”