We Already Use Bayes' Formula

Via John Earman.

I guarantee you that everyone uses Bayes' formula whenever considering new information. We ask ourselves implicitly and/or explicitly what the Pr (probability) is of a new H (hypothesis) given E (evidence) and our K (background knowledge).

That is, when considering a new hypothesis we fact-check it based on the evidence plus our existing background knowledge.  

Of course we do this imperfectly, sometimes woefully so, but we try.

The only question left is when and where should we use the the math.