Thomas Kelly

Epistemic partialism is the view that friends have a doxastic duty to overestimate each other. If one holds that there are no practical reasons for belief, we will argue, one has to deny the existence of any epistemic duties, and thus reject epistemic partialism. But if it is false that one has a doxastic duty to overestimate one’s friends, why does it so often seem true? We argue that there is a robust causal relationship between friendship and overestimation that can be mistaken for a constitutive relationship; we also argue that one can still accept some of the normative intuitions that motivate epistemic partialism even if one rejects epistemic partialism itself. Along the way, we consider and reject a watered-down version of epistemic partialism—call it epistemic partialism-light—according to which one has a duty to take steps to create in oneself a disposition to overestimate one’s friends.

Deference principles are principles that describe when, and to what extent, it’s rational to defer to others. Recently, some authors have used such principles to argue for Evidential Uniqueness, the claim that for every batch of evidence, there’s a unique doxastic state that it’s permissible for subjects with that total evidence to have. This paper has two aims. The first aim is to assess these deference-based arguments for Evidential Uniqueness. I’ll show that these arguments only work given a particular kind of deference principle, and I’ll argue that there are reasons to reject these kinds of principles. The second aim of this paper is to spell out what a plausible generalized deference principle looks like. I’ll start by offering a principled rationale for taking deference to constrain rational belief. Then I’ll flesh out the kind of deference principle suggested by this rationale. Finally, I’ll show that this principle is both more plausible and more general than the principles used in the deference-based arguments for Evidential Uniqueness.