Radical probabilism is a hypothesis in philosophy, in particular epistemology, and probability theory that holds that no facts are known for certain.
If the learner subsequently learns that B is true, nothing in the axioms of probability or the results derived therefrom tells him how to behave.
[2] The dynamic Dutch book argument for Bayesian updating has been criticised by Hacking,[1] Kyburg,[3] Christensen,[4] and Maher.
[9] In this case Bayes' rule isn't able to capture a mere subjective change in the probability of some critical fact.
It seems reasonable, as a starting position, to adopt the law of total probability and extend it to updating in much the same way as was Bayes' theorem.
[2] Jeffrey advocated this as a rule of updating under radical probabilism and called it probability kinematics.