This is the first post in what I hope will be a series on the historical evidence for Christianity. The views on this are enormous in variation, from those who think Christianity completely unsupported by history to those who believe that the historical evidence for it is so strong that only someone suppressing the truth could remain an unbeliever. My view is in the middle. There is as positive historical case to be made for Christianity, but it depends on what's in the rest of a person's belief system whether that case is sufficient.
The model I’d like to use to discuss this is one using Bayes’ Theorem. I had trouble showing BT on my blog, so I am expressing it here.
P(B) x P(A|B)
Let’s take B to be the thesis that the founding of Christianity involved action by God or some other powerful supernatural agent. Not-B, on the other hand, would be the view that Christianity was founded without the aid of any beings of superhuman power, that ordinary natural causation produced all the events which resulted in the spread of Christianity on earth. A would be the various pieces of historical evidence which can be brought forward to bear on this issue.
P(B) in this theorem would be the initial probability that the founding of Christianity was miraculous, before we examine the specific historical evidence. The problem here is that I know of no way to objectively measure the antecedent probability of anything. In fact, I am pretty much a subjectivist Bayesian. I think that people have personal prior probabilities and they ought to alter those initial probabilities as evidence comes in , but I don’t know of any way to actually prove that one set of initial probabilities is correct and another is not. Some people have maintained that it is possible to go from how frequently an event has occurred in the past to how antecedently likely it is to occur now, but the problem is that every singe event falls under a range of classes. Hume didn’t use Bayes’ theorem, but if he did he would have said that miracles are event-types that occur so infrequently in experience that the prior probability for them so low as to make belief unreasonable no matter what the other figures are. C. S. Lewis’s book Miracles was a book called Miracles: A Preliminary Study, meaning that his argument was designed to show that the antecedent probability for the miraculous should not be vanishingly low. I am going to presuppose that different people will have different priors for miracles.
P(A/B) is the likelihood that the pieces of evidence should exist on the assumption that God was involved in the founding of Christianity. If God were miraculously involved in, say the resurrection of Jesus, should we expect to find a new movement arising based on the claim, would it make sense of a Jewish group arising that changed the Sabbath from Saturday to Sunday, etc.
P(A) is how likely it is that these event should have occurred whether or not there was any miraculous involvement. Is what happened in the life of Jesus and the founding of Christianity likely to have happened. Perhaps human gullibility and fallibility is such that people would have come up with something like this anyway, even without divine intervention.
I’m going to set aside the issue of prior probabilities and ask the question of whether P (A/B) is signiicantly greater that P/A. If it is, then there is a confirming argument for Christianity to be found in history, even if, according to many people’s credence function, it is insufficient to secure acceptance for Christianity. If it is not significantly greater, then there is no confirming argument for Christianity to he had from history.
This is a link to my Infidels essay on miracles, which should help understand the basic concepts.