Most scholars who write about the ancient world feel obliged to warn their readers that our knowledge can be at best partial and that certainty is seldom attained. A book about a first-century Jew who lived in a rather unimportant part of the Roman empire must be prefaced by such a warning. We know about Jesus from books written a few decades after his death, probably by people who were not among his followers during his lifetime. They quote him in Greek, which was not his primary language, and in any case the differences among our sources show that his words and deeds were not perfectly preserved. We have very little information about him apart from the works written to glorify him. Today, we do not have good documentation for such out-of-the-way places as Palestine; nor did the authors of our sources. They had no archives and no official records of any kind. They did not even have access to good maps. These limitations, which were common in the ancient world, result in a good deal of uncertainty.
“Preface,’ The Historical Figure of Jesus. E. P. Sanders.