The heuristic use of conditionalisation

Abstract I provide an example in which Bayesian conditionalisation fails to validate plausible claims about rational permissibility. The example suggests that conditionalisation should be treated as a heuristic principle: useful in many situations, but not all. This raises the question of how to characterise the cases in which it is appropriate to use conditionalisation. I show that one can answer this question by appealing to the framework of objective Bayesian inductive logic to provide sufficient conditions for the applicability of conditionalisation.