Abstract

Almost everyone agrees, under some interpretation, that a world is nomologically accessible if and only if it obeys the laws of the base world. This surface agreement, however, has led many to attach little importance to different interpretations, thereby conflating two distinct concepts of nomological accessibility. According to the Shared Law Account (hereafter SL), a target world is nomologically accessible from the base world if, and only if, all and only the laws of the base world are laws at the target world. The Compossible Events Account (hereafiter CE) holds that a target world is nomologically accessible from the base world if, and only if, all events of the target world are compossible with the laws of the base world. After demonstrating that these accounts are distinct, I shall show that the distinction matters. Not only is the correct modal system for nomic necessity determined by which characterizes accessibility, but some arguments against Humean supenfenience depend upon SL. In the final section I show that CE is the correct interpretation.