De Finetti and Savage on the normative relevance of imprecise reasoning: a reply to Arthmar and Brady

This paper examines the claim that de Finetti and Savage completely rejected the notion of indeterminate, as distinct from imprecise, probabilities. It argues that their examination of imprecise reasoning refers both to descriptive and normative issues, and that the inability for a decision-maker to commit to a single prior cannot be limited to measurement problems, as argued by Arthmar and Brady in a recent contribution to this Journal. The paper shows that de Finetti and Savage admitted that having an interval of initial probabilities may sometimes have normative relevance, thereby leaving an opening for indeterminate probabilities.