Principles of Indifference

Abstract

The principle of indifference (PI) states that in the absence of any relevant evidence, a rational agent will distribute their credence equally among all the possible outcomes under consideration. Despite its intuitive plausibility, PI famously falls prey to paradox, and so is widely rejected as a principle of ideal rationality. In this article, I present a novel rehabilitation of PI in terms of the epistemology of comparative confidence judgments. In particular, I consider two natural comparative reformulations of PI and argue that while one of them prescribes the adoption of patently irrational epistemic states, the other (which is only available when we drop the standard but controversial “Opinionation” assumption from the comparative confidence framework) provides a consistent formulation of PI that overcomes the most salient limitations of existing formulations.