Here’s a good explanation of Bayes theorem, and its limitations. It isn’t a magic explanation, it is a limited tool to be used in assocation with an appropriate probability model.

This post follows from the previous review of Richard Carrier’s “Proving History”, which attempts to use Bayes’s Theorem to prove Jesus didn’t exist. In my review I point out a selection of the mathematical problems with that book, even though I quite enjoyed it. This post is designed to explain what Bayes’s Theorem actually does, and show why it isn’t particularly useful outside of specific domains. It is a journey through basic probability theory, for folks who aren’t into math (though I’ll assume high-school math). It is designed to be simple, and therefore is rather long. I will update it and clarify it from time to time. [Edit: There is also a new post on errors, which follows on from this].

Let’s think about the birth of Christianity. How did it happen? We don’t know, which is to say there are a lot of different things that could…

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