Macro-Level and Micro-Level Chances

This chapter discusses conceptual problems that may arise if we think of the Best System as giving us two (potentially) different chances for the same macroscopic event: one that arises by mathematical entailment out of chancy microphysics, and a second one that is in the system because it supervenes directly on the pattern of events at the macro level. Given the pragmatic approach of HOC, such dual-chance-value situations could exist, though there are formidable conceptual difficulties about how to derive probabilities for macroscopic event-types from micro-level chance laws. It is argued that if such dual-value situations exist in the Best System, one would have reason to apply PP to the macro-level chance rules, but not to the micro-derived chances. The discussion reveals a heretofore hidden limitation of both HOCs themselves, and the validity of the arguments from chapter 4 justifying PP. But the limitation is of no practical consequence.