Deficiency of Probabilistic Approach for Settling Voltaire’s Objection

According to a popular version of Inference to the Best Explanation (IBE), the hypothesis that provides the best explanation for a group of phenomena is probably true. One of the key objections against this line of thought is Voltaire’s objection. According to this objection, we have no reason to believe that the criteria for selecting the best explanation provide the likeliest explanation. In this paper, we address Voltaire’s objection from probabilistic (Bayesian) point of view. To be exact, we scrutinize this question: based on probability axioms and their consequences, including Bayes’ theorem, is it justified to think of the best explanation as the likeliest one? Considering this question, first of all, we show that, although IBE is a prima facie case of Bayesianism, probabilistic approach is not fundamentally consistent with IBE. Secondly, it will be argued that the best explanation which is favored over its rivals by scientists is not always the likeliest one. Moreover, we show that Bayes’ theorem overlooks the evidence for which the explanatory hypotheses in IBE compete. Thus, probabilistic approach is unable to settle Voltaire’s objection.