Bayes theorem and the anthropic principle

Years ago I used to teach Bayes theorem to informatics grad students.

I was reassigned to other lectures though. Truth is, I had a hard time focusing on the boring stuff we were doing with Bayes. It just seemed like there was a deep weirdness about the Bayesian model of probability, but I couldn't quite put my finger on it. I was sure someone who understood it deeply would justify my queasiness.

Since then there's been a bit of a renaissance in thinking about Bayes. In Our Time even did a recent programme with a good bit of Bayes. Physicists are all over Bayes these days, and the Bayesian vs. Frequentist combat is out in the open (I knew this stuff was weird).

These days, I could assign students this essay to read:

PHYS771 Lecture 17: Fun With the Anthropic Principle

... So if Bayes' Theorem seems unobjectionable, then I want to make you feel queasy about it. That's my goal. The way to do that is to take the theorem very, very seriously as an account of how we should reason about the state of the world...

Of course that assignment might also shrink the class size ...