Daily Archives: 2018-07-07 20:36:05 UTC

Clarification needed for my reply to McGrath’s criticism of the use of Bayesian reasoning

McGrath does not tell his readers in the post we are addressing what he has in mind as the “clear-cut” evidence for the historicity of Jesus but from previous posts and comments I am convinced that it is the “brother of the Lord” passage in Galatians 1:19 that he has in mind. If I am wrong then someone will no doubt inform me.

I ought to have made that point clearer in my original post.

If someone can direct me to where McGrath recently made the point about that Galatians passage (was it in response to the reddit discussion about Vridar?) I would much appreciate it.

 

 

Reply to James McGrath’s Criticism of Bayes’s Theorem in the Jesus Mythicism Debate

Aviezer Tucker

James McGrath in a recent post, Jesus Mythicism: Two Truths and a Lie, made the following criticism of the use of Bayes’s theorem in the Jesus Mythicism debate:

. . . . as I was reminded of the problematic case that Richard Carrier has made for incorporating mathematical probability (and more specifically a Bayesian approach) into historical methods. . . .

If one followed Carrier’s logic, each bit of evidence of untruth would diminish the evidence for truth, and each bit of evidence that is compatible with the non-historicity of Jesus diminishes the case for his historicity.

The logic of this argument is based on a misunderstanding of the nature of historical inquiry and how a historian is expected to apply Bayesian logic. (It also misconstrues Carrier’s argument but that is another question. I want only to focus on a correct understanding of how a historian validly applies Bayesian reasoning.)

In support of my assertion that James McGrath’s criticism is misinformed I turn to a historian and philosopher of history, Aviezer Tucker (see also here and here), author of Our Knowledge of the Past: A Philosophy of Historiography. He treats Bayesian reasoning by historical researchers in depth in chapter three. I quote a section from that chapter (with my own formatting):

There have been attempts to use the full Bayesian formula to evaluate hypotheses about the past, for example, whether miracles happened or not (Earman, 2000, pp. 53–9).

We may compare McGrath’s criticism. He is of the impression that the Bayesian formula is used to evaluate the hypothesis that Jesus did exist. This is a common misunderstanding. If you are confused, continue to read.

Despite Earman’s correct criticism of Hume (1988), both ask the same full Bayesian question:

“What is the probability that a certain miracle happened, given the testimonies to that effect and our scientific background knowledge?”

We may compare McGrath’s criticism again. He is of the impression that the historian using Bayesian logic is asking what is the probability that Jesus existed, given the testimonies to that effect and our background knowledge. If you are still confused then you share McGrath’s misunderstanding of the nature of historical inquiry. So continue with Tucker:

But this is not the kind of question biblical critics and historians ask. They ask,

“What is the best explanation of this set of documents that tells of a miracle of a certain kind?”

The center of research is the explanation of the evidence, not whether or not a literal interpretation of the evidence corresponds with what took place.

(Tucker, p. 99)

In other words, biblical critics and historians ask (Tucker is assuming the biblical critic and historian is using Bayesian logic validly and with a correct understand of the true nature of historical research) what is the best explanation for a document that, say, purports to be by Paul saying he met the James, “the brother of the Lord”.

I use that particular example because — and someone correct me if I am mistaken — Jame McGrath and others believe that passage (Galatians 1:19) makes any questioning of the historicity of Jesus an act of “denialism”. (McGrath does not tell his readers in the post we are addressing what he has in mind as the “clear-cut” evidence for the historicity of Jesus but from previous posts and comments I am convinced that it is the “brother of the Lord” passage in Galatians 1:19 that he has in mind. If I am wrong then someone will no doubt inform me.)

No one, I am sure, would mean to infer that the late and highly respected Philip R. Davies was guilty of denialism when he suggested that the historical methods he applied to the Old Testament should also be applied to the New — a method I have sought to apply to the study of Christian origins ever since I read Davies’ groundbreaking book.

Back to the question. It is the question of what is the best explanation for the passage in our version of Galatians that I have attempted to address several times now.

That is the question that the historian needs to ask. Every decent book I have read for students about to undertake advanced historical studies has stressed, among many other duties, the necessity for the researcher to question the provenance, the authenticity, of the documents he or she is using, and to know all the questions related to such questions from a thorough investigation of the entire field. My several posts have attempted to introduce such questions that should be basic to any historical study.

Tucker, from my reading of his book, would not consider such an exercise to be “denialism”, but sound and fundamental historical method — and even sound biblical criticism. read more »