How do desires explain motivated reasoning?

A motivated reasoner reasons as she does because of what she wants to believe. But what exactly does the “because” here communicate? That is, how do the motivated reasoner’s desires explain why she reasons as she does? In this essay, I argue that the explanation in question is a manifesting explanation. Just as a glass breaking manifests fragility, motivated reasoning manifests a desire to (not) believe. One significant advantage of this picture is that it helps us understand why motivated reasoning is problematic. Coupled with a few minimal, independently motivated ideas, it reveals that motivated reasoning involves, roughly, a lack of concern for believing in line with the available evidence: a distinctively epistemic defect in the reasoner’s will, analogous to the moral defect in the will of someone who disregards morality’s demands. As a bonus, I’ll suggest, this picture points towards a promising way of thinking about epistemic blameworthiness.