Unsharp Best System Chances

Much recent philosophical attention has been devoted to variants on the Best System Analysis of laws and chance. In particular, philosophers have been interested in the prospects of such Best System Analyses (BSAs) for yielding high-level laws and chances. Nevertheless, a foundational worry about BSAs lurks: there do not appear to be uniquely appropriate measures of the degree to which a system exhibits theoretical virtues, such as simplicity and strength. Nor does there appear to be a uniquely correct exchange rate at which the theoretical virtues of simplicity, strength, and likelihood (or fit) trade off against one another in the determination of a best system. Moreover, it may be that there is no robustly best system: no system that comes out best under any reasonable measures of the theoretical virtues and exchange rate between them. This worry has been noted by several philosophers, with some arguing that there is indeed plausibly a set of tied-for-best systems for our world (specifically, a set of very good systems, but no robustly best system). Some have even argued that this entails that there are no Best System laws or chances in our world. I argue that, while it is plausible that there is a set of tied-for-best systems for our world, it doesn’t follow from this that there are no Best System chances. (As I will argue, the situation with regard to laws is more complex.) Rather, it follows that (some of) the Best System chances for our world are unsharp.