Justifying the principle of indifference

Eur J Philos Sci. 2018;8(3):559-586. doi: 10.1007/s13194-018-0201-0. Epub 2018 Mar 13.

Abstract

This paper presents a new argument for the Principle of Indifference. This argument can be thought of in two ways: as a pragmatic argument, justifying the principle as needing to hold if one is to minimise worst-case expected loss, or as an epistemic argument, justifying the principle as needing to hold in order to minimise worst-case expected inaccuracy. The question arises as to which interpretation is preferable. I show that the epistemic argument contradicts Evidentialism and suggest that the relative plausibility of Evidentialism provides grounds to prefer the pragmatic interpretation. If this is right, it extends to a general preference for pragmatic arguments for the Principle of Indifference, and also to a general preference for pragmatic arguments for other norms of Bayesian epistemology.

Keywords: Accuracy; Bayesianism; Epistemic consequentialism; Principle of indifference.