The Principle of Total Evidence: Justification and Political Significance

The principle of total evidence says that one should conditionalize one’s degrees of belief on one’s total evidence. In the first part, I propose a justification of this principle in terms of its epistemic optimality. The justification is based on a proof of I. J. Good and embedded into a new account of epistemology based on optimality-justifications. In the second part, I discuss an apparent conflict between the principle of total evidence and the political demands of anti-discrimination. These demands require, for example, that information about the sex of the applicant for a job should not be included in the relevant evidence. I argue that if one assesses the applicant’s qualification in terms of those properties that are directly causally relevant for the job performance, then properties that are merely indirectly relevant, such as sex, race, or age, are screened off, i.e., become irrelevant. So, the apparent conflict disappears.