@article{Belnap2007-BELPAP,title = {Propensities and Probabilities},volume = {38},number = {3},year = {2007},journal = {Studies in History and Philosophy of Science Part B},author = {Nuel Belnap},pages = {593--625},abstract = {Popper's introduction of ``propensity'' was intended to provide a solid conceptual foundation for objective single-case probabilities. By considering the partly opposed contributions of Humphreys and Miller and Salmon, it is argued that when properly understood, propensities can in fact be understood as objective single-case causal probabilities of transitions between concrete events. The chief claim is that propensities are well-explicated by describing how they fit into the existing formal theory of branching space-times, which is simultaneously indeterministic and causal. Several problematic examples, some commonsense and some quantum-mechanical, are used to make clear the advantages of invoking branching space-times theory in coming to understand propensities.}}@