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It's simply the way Bayesian statistics work: if the prior probability of something happening is very low, then for me to flip from thinking "didn't happen" to
by ewjordan 16y ago
It's simply the way Bayesian statistics work: if the prior probability of something happening is very low, then for me to flip from thinking "didn't happen" to "did" it will take some new information that is very powerful.
If you think that's illogical, I'd ask you to consider why a teacher is more likely to accept the excuse "my dog ate my homework" than "aliens kidnapped me and stole it". You seem to be arguing that given that the evidences are equal (a mere statement from a kid), the teacher should properly consider both occurrences to be equally likely.
- lukev 16y agoThis is true, but I'd add a caution: just because something seems outlandish or improbable doesn't mean it actually has a low prior probability. Human intuition on what's weird and what's not is not a reliable oracle of prior probability. If you're going to give the prior an actual number, you better base it on actual facts. In your example, based on existing data, it is indeed fair - some dogs do sometimes eat homework, whereas there are no verified accounts of aliens stealing it. So that's a legitimate adjustment of priors. Particularly if you actually have data on the incidence of paper-hungry dogs. But in science and philosophy, there's lots of important questions for which we can't legitimately calculate priors, and "it would be too weird" is not at all relevant when determining their values.
- phob 16y agoBut we do have reasonable priors on parapsychology from its wasteland of unreplicated, flawed studies, with no convincing results despite decades of effort.