Inference to the Best Explanation Made Incoherent

Abstract

Defenders of Inference to the Best Explanation (IBE) claim that explanatory factors should play an important role in empirical inference. They disagree, however, about how exactly to formulate this role. In particular, they disagree about whether to formulate IBE as an inference rule for full beliefs or for degrees of belief, and, if it is formulated as a rule for degrees of belief, how this rule relates to Bayesianism. In this essay I advance a new argument against non-Bayesian versions of IBE that arises when we are concerned with multiple levels of explanation of some phenomenon. I show that in many such cases, following IBE as an inference rule for full belief leads to deductively inconsistent beliefs, and following IBE as a non-Bayesian updating rule for degrees of belief leads to (synchronically) probabilistically incoherent degrees of belief.