In my last post, I addressed a common excuse atheists use to avoid dealing with testimony of God’s interactions with history: misuse of prior probability. Just because a particular event does not have precedent doesn’t mean it can be handwaved; a prior probability that is undefined cannot be treated as a prior probability of zero. Before July 16, 1945, there had never been such thing as a nuclear bomb, but that didn’t stop Trinity from going off.
As an example, I suggested a botched alien landing, evidenced for archeologists in the testimonies of a prehistoric people and a handful of complex mathematical engravings. Now, whether that is sufficient evidence doesn’t matter; the point is that we’d theoretically be willing to evaluate this evidence despite having no prior experience with alien landings and no reasonable way to estimate the prior probability of an alien landing.
However, several commenters responded by arguing that the analogy of an alien landing was improper, that these hypothetical aliens would necessarily be part of nature. An alien landing, while unprecedented, wouldn’t break any of the laws of physics, and so it’s not on the same level with a miracle. Read more of this post
When it becomes apparent that Christians like myself are depending primarily on history for empirical evidence of God’s involvement in history (imagine that!), atheists quite often appeal to probabilities….specifically, Bayesian probability.
Now, Bayesian probability is a complicated subject, but the relevant point here is that the probability of a particular event (or of a particular explanation being true) depends on its prior probability: the base rate of that particular event within the general population of events. Simply put, if a particular event is already known to be extremely rare, this “rareness” needs to be included in evaluating evidence for that event.
Bayes’ Theorem (image by mattbuck)
This becomes particularly important when we’re comparing competing explanations. Even if the evidence seems to point more toward one explanation, that explanation might not be the most probable if it was already very unlikely. For example, hearing a loud thunderous roar outside is good evidence that there’s a thunderstorm….unless, of course, you live in the desert outside Baghdad, where thunderstorms are vanishingly rare and roadside bombs are much more frequent. Read more of this post