Bayes’ rule is a mathematical recipe for going from what we already know (the prior) to what we should believe next (the posterior), based on what we are learning now (the likelihood). Priors, likelihoods, and posteriors are often called Bayesian ‘beliefs’ because they represent states of knowledge rather than states of the world. (Note that a Bayesian belief is not necessarily something I-as-a-person believe. It makes equal sense to say that my visual cortex ‘believes’ that the object in front
