Tuesday, December 03, 2019

Do miracles have a higher burden of proof?

This is something I frequently discuss because it's a mainstay of atheism. Atheists typically say there's an overwhelming presumption against miracles. In addition there are Christian Bayesian theorists who say miracles have a higher burden of proof, but it's not insurmountable. Let's take a couple of comparisons.

Suppose I'm abducted and sedated. Next thing I know I wake up in the middle of nowhere. A wilderness with a river nearby. Is it safe for me to wade in the river?

Some rivers are hazardous.  Some rivers are frequented by crocodiles, anacondas, electric eels, or bull sharks.

What's the antecedent probability that the river is safe or hazardous to wade in? Unless I know where I am, I have no frame of reference. There's no presumption one way or the other to overcome.

I can't begin to calculate the probabilities in a vacuum. I need to know where I am.

Or take another example. Suppose a driver spots a license plate in the parking lot. What are the odds that that car would be at the same time and place he was? In principle, you could consider the number of in-state license plates, and make an educated guess about out-of-state drivers.

But suppose the driver is a bookie on the run from the mafia, and the car with that particular license plate belongs to triggermen who are shadowing him. That drastically changes the odds.

Now in Bayesian probability theory, as I understand it, you divvy up the odds into prior and posterior probabilities. The prior improbability may be high, but that can be overcome with more specific evidence.

But my problem is that if the probability theorist already has all the information when he begins his analysis, why bifurcate the evidence into prior and posterior compartments? Why artificially bracket off some of what he knows to assign a prior probability value, which creates a presumption that must then be overcome? What's the point? It's not like he discovered new evidence in the process of his analysis.

I don't think it's meaningful to lay odds on miracles in the abstract. It depends on the kind for world we live in as well as specific evidence for specific reports.