Principle of Analogy

I recently found the name for a simple and common sense idea that is often abused in apologetics circles, the Principle of Analogy.

Bob Price described it this way:

We don’t know that things have always happened the way they do now.  But unless we assume that, we can’t infer anything about the past.  If we don’t assume that physics and chemistry have always worked by the same laws, we’re just going to believe anything any nut says.  …

[Imagine being confronted with the claim,] “I met a guy today who turned into a werewolf when the full moon came out.”  Wait a minute—I know of no one who has ever seriously claimed to have ever seen that, so there is no analogy to current day experience to such a claim.  But … there are fictional stories and movies where that happens.  I bet this really is one of those.  (Source)

How do we categorize a miracle claim from history?  What’s it analogous to?  Does it look like the plausible activities of ordinary people or does it look like legend?  You can’t say for sure, of course, but which bin does this claim best fit into?

Did a winged horse carry Muhammad?  Did Joseph Smith find golden plates with the help of the angel Moroni?  Can faith healers cure illness that modern medicine can’t?  Science has no analogy to these claims, but mythology and legend do.

Incredibly, I’ve heard Christians reject this principle and argue that an atheist must bring positive evidence against their claims.  Say for example that the question is whether Jesus raised Lazarus from the dead.  The Christian points to this story in the gospel of John—that’s the evidence in favor.  And then he says, “So where’s your evidence against?”

Of course, I have no direct evidence against this particular event.  I have no direct evidence that Jesus didn’t raise Lazarus or that Merlin wasn’t a shape-shifting wizard or that Paul Bunyan didn’t exist.  The plausibility test that we all use helps ensure that we don’t simply believe everything we hear or read.  Well, all of us, I guess, except someone who’s eager to make exceptions to preserve a preconception.

Something can violate the Principle of Analogy only with substantial evidence.  The claim “I can see through opaque objects” properly fit into the magical category until Wilhelm Röntgen demonstrated x-rays.

Until we have an analogy to a miracle story, it properly belongs in the magical category as well.

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  • The Bob Price quote was from a 4/11/2010 interview titled “How to Study the Historical Jesus” from Common Sense Atheism.  The MP3 file is here (go to 13:30).