Intertranslating Counterfactuals and Updates

We recall that the Ramsey Rule can be seen as axiomatising the relationship of inverse accessibility relations which exists between the notions of update and counterfactual conditional. We use this fact to translate between postulates for updates and postulates for counterfactuals. Thus, Katsuno/Mendelzon's postulates U1{U8 are translated into counterfactual postulates C1{C8 (theorem 6), and many of the familar counter-factual postulates are translated into postulates for updates (theorem 7). Our conclusions are summarised in table 5.