Many have remarked, with some chagrin, in the sundry conclusions of academics writing books and articles on the historical Jesus. The lack of unanimity bothers me less than it may others, for historical and religious studies belong not to the sciences but to the humanities, and waiting for a consensus on any noteworthy subject within the latter is like waiting for Godot. The main point here, however, is that the traditional criteria, which were devised as checks and balances for our subjectivity, have not delivered. The scope of diversity proves that we are still as embedded as ever in that subjectivity. All our methodological erudition, our repeated attempts to refine and heed criteria, have failed to impose order on our discipline: the Jesus of one book often does not look much like the Jesus of another book, even when those books employ more or less the same method. Surely we are no closer to any uniformity of results to-day than we would have been had we never heard of dissimilarity, multiple attestation, coherence, and embarrassment.
Doing history, which is an art requiring imagination and conjecture, cannot be identified with the mechanical observances of directives. The rules of chemistry mean that, if you follow the instructions, you will get the same result as everybody else. The criteria of authenticity are more like the rules of language: you can use them to say just about anything.
Dale C. Allison, Jr. The Historical Christ and the Theological Jesus (Grand Rapids, MI: Eerdmans, 2009), location 762 (Kindle edition).