 This says that your credence in q should be whatever you take the maximally rational credence to be for your situation, an idea that seems hard to argue with. It is a variant of a principle used by Haim Gaifman (1988) to construct a theory of higher-order probability. There the role of \(P_{M}\) was given to what has become known as an expert function corresponding, in his use, to the probabilities of a subject who has maximal knowledge.