Sunday, May 08, 2011

On the use of probability theory in the philosophy of religion

I have a take on the role of probabilistic arguments that might be of help here. Look, when it comes to the resurrection of Jesus, a person's decision to accept or not accept the Resurrection is likely to be a combination of the evidence specific to the Resurrection, and a prior assessment of how likely the background beliefs that are behind belief in the resurrection are to be true. We know that people who are thinking about the Resurrection are bound to differ about whether the claim that Jesus rose from the dead is antecedently plausible. There's going to be people who find the fact that something would have to be explained as a divine miracle grounds for giving it as close to a probability of zero as you can get. There are some people who are already committed to some form of supernaturalism, and who are not going to be deterred by the fact that the explanation involves the miraculous. So, how can we carry on the discussion? One way of doing it is to ask merely whether the evidence in more like what we should expect if the Resurrection happened, or whether it's more like what we should expect if it didn't.  In other words, is there anything in the reports coming out of the first-century church that is more like what you should expect if Jesus was raised than if Jesus was not raised. If the answer to that question is yes, then the evidence confirms the resurrection, but it might still be rejected by reasonable people on the grounds that a Resurrection would commit you to the existence of God, or other features of Christianity that you consider to be improbable. Fine, but you can at least say, in response to the evidence, that the evidence directly bearing on the resurrection of Jesus is easier to explain if the Resurrection occurred than if it didn't. In other words, we can isolate one particular piece of evidence from the total evidence we have that bears on the issue and ask whether this piece of evidence supports the Christian claim that Jesus was resurrected or not.

Similarly, we can ask, concerning the fact of pain and suffering, how it impacts the credibility of theism. It could turn out that yes, pain and suffering adversely affects the credibility of theism, but it does not show that anyone who believes in the existence of God is just being delusional.

I understand that some people do Bayesian probability theory to get a correct final conclusion based upon agreed-upon methods for ascertaining probabilities. That's legitimate, but we also might like to isolate the impact of a piece of evidence on the overall plausibility of theism and Christianity. I find Bayes' theorem to be a helpful tool in doing that, even though I do not expect an agreed-upon conclusion concerning the Resurrection after we are done. To me, it's not a misuse of Bayes' theorem, just a different use.


Brenda said...

I think it highly likely that the people of that time *believed* that Jesus rose from the dead and that their belief fully explains the historical the accounts we have. I can see no reason whatsoever to think such an event actually happened or is even possible.

I don't happen to believe that the existence of pain and suffering make theism untenable. I know people who seek to be free of suffering. We call them junkies.

Still, what one believes is possible is going to strongly influence how you asses the probability of some event happening so it is important to be sure that one's basic assumptions are based in reality or science, what is in fact the case, rather than one's fantasy or desire about what one believes ought to be the case.

David B Marshall said...

Prior probability is, indeed, almost as important as the historical evidence itself. Evangelicals often concentrate on the latter, and forget the former -- though I think a good case can be made that prior probability is quite high.

Or to give this a little twist, what probability would you assign a report that Osama bin Laden rose from the dead?

I don't know how important the actual numbers are, though -- it's all pretty rough, of course. I'm glad Tim explained his thinking on that -- I'd read his article, but had recently seen a gross misrepresentation of it, linked from John Loftus' site.

cl said...


I'd imagine you've seen it, but if not DePoe on Bayes and the Resurrection:

“…my goal is to apply EBT to testimonial arguments for the historicity of the Resurrection as an objective tool to disentangle mere personal opinion from evidential support.” DePoe recognizes the difficulty of assigning specific figures and opts instead for ranges he hopes “the atheist and theist alike could be happy with.” Generous indeed, DePoe is willing to disqualify all but 10 of the 520 witnesses recorded in the New Testament. After noting that “even with charitable values for each term the evidence for R is compelling,” DePoe turns to objections from John Earman, one of which is to claim defect in Bayesian analysis of multiple witnessing or Bayesianism itself, two of which essentially consist of assigning non-charitable prior probabilities without sufficient reason. After brief but compelling responses to Humean critique of miraculous testimony, DePoe concludes: “…the EH account presents a plausible way to demonstrate the overwhelming evidential case for the Resurrection–even while using diminished values for the evidence that many non-believers would find acceptable. Therefore, it is rational to believe that the eyewitnesses testify truly…”

The full PDF can be downloaded from the "Papers" tab on my blog, if anyone's interested.

Victor Reppert said...

DePoe got his Masters at Western Michigan University.