A few readers have indicated to me that my recent series of posts on the problematic use of Bayes Theorem for assessing “historical claims” have failed to make their intended point.
Hopefully here I can succinctly explain why Bayes cannot help us decide whether Christianity began with a historical Jesus.
Reason #1: If our question is simply, Did Jesus Exist? then it is meaningless. What is of interest is the question of how Christianity originated. What might Jesus have done that gave birth to the Christian religion? What did others do during the time of Jesus or after him that shaped or established Christianity? Those are the meaningful questions. Simply saying Jesus did or did not exist is somewhat pointless — unless, perhaps, one wants a negative answer in order to irritate believers.
Reason #2: If by using Bayes one concludes that Jesus “probably did not exist” then again, we have to ask, So what? If it appears unlikely that he existed then after weighing up the probabilities on the basis of the various strands of data, that tells the historian nothing useful at all. Simply saying that Jesus fits the pattern of mythical persons, if that’s where Bayesian inference leads, does not answer the question of whether he existed or not. Simply saying that there is, say, an 80% chance he did not exist still leaves open the possibility that he did exist. So what has been achieved? Nothing useful for the historian at all. Likewise, calculating that there is an 80% chance that he did exist would still leave open the possibility that he did not. The historian is no better off with either result.
I suspect King Philip II of Spain saw the odds of his Spanish Armada crushing the English fleet as overwhelmingly high. The odds against an event happening are irrelevant are irrelevant if they happen. And many times the unexpected and “out of the blue” does happen in history. That they may have been judged to have been unlikely at the time makes no difference to the fact that they happened and are part of the historical record.
Most historical events are “unlikely” or unforeseen until after they happen. After they happen commentators and the rest of us can see how “inevitable” they were. We can always predict what will happen after it happens. Carrier’s mythicist hypothesis can predict the type of evidence the historian will find after the hypothesis was originally formulated on the basis of that evidence. One might look at any number of events in the past and ask, What was the likelihood of X happening? The chances that I will be struck by lightning are very slim indeed. But if I were to be struck by lightning this weekend — stormy weather appears to be approaching — the odds against it happening will mean absolutely nothing against the fact (fingers crossed it won’t be a fact) that it “happened”! Odds against something happening are meaningless when investigating “what did happen”.
We don’t need Bayesian calculations to decide whether there was a Roman empire, or whether its emperors were worshiped as deities, or whether the Roman power destroyed the Jewish temple in 70 CE. The kind of evidence we have for the “raw facts” of the past, including who lived and who did what, are grounded in the same kinds of judgments we make in testing the authenticity of modern claims, whether they be events reported in the news or checking the reliability of advertised claims about a product that interests us. Some of us are less careful with respect to such matters than is healthy and easily believe false claims, present and past. When a historian is interested in whether “new facts” can be dug up to throw new light on a question, it is to the archives, to official records, to diaries and letters and reports of various kinds that they turn. These are tested for authenticity and reliability. If there is doubt about any detail it is more likely to find its way into publication by way of a footnote — with its questionable status clearly noted.
The only justifiable approach to reconstructing Christian origins is to build on the sources we have and on what we know about them — not on what we surmise about them. That approach will not allow us to join in the games of imagining what Jesus and his followers may have done. (We have stories of Jesus and we cannot assume — without justification that would pass the test in any other field of sound empirical inquiry — that they must be based on true events.) We will not have the wealth of details we would like if we avoid make-believe games. But the professional will not apologize for tailoring the question and scope of inquiry to accord with the extent and nature of the source material.
Sure, there is room for Bayesian probability when it comes to drawing certain kinds of inferences from archaeological data or for comparing the likelihood of competing hypotheses, but claiming that so-and-so did or did not exist is by itself a rather meaningless exercise for the reason I stated above.
(See also the section of my earlier post pointing out that not even postmodernist historians work with “what probably happened“.)
To address one specific point I referred to in my recent series: It may well be that one can find in literature more mythical persons who fit a Rank-Raglan hero type, but that is irrelevant to the fact that some historical persons did resurface in later literature wearing Rank-Raglan features (born of a virgin, died on a hill, etc). But even Raglan himself understood that the historicity of a figure was unrelated to the fact that fanciful tales were later told about him or her. If Jesus scores more highly than other historical figures on the R-R scale, so be it: such a “fact” would have no bearing whatever on whether or not he might have been historical. Ask Raglan himself.