This book is the first comprehensive treatment of the idea that some facts call for explanation. This idea serves as a premise in influential arguments for the inexistence of moral facts, for the inexistence of mathematical facts, for the existence of a god, for the existence of multiple universes, and other topics. Despite its prevalence and importance in debates across fields of study, however, this premise is rarely questioned, and the distinction between facts that call for explanation and those that do not has thus far received little careful attention. According to what Baras calls the naïve picture, facts possess a certain property, which he calls strikingness, to different degrees. To the extent that a fact has this property, it calls for explanation. We feel compelled to figure out what this property is, and what special explanation amounts to, but this approach, Baras argues, leads to a dead end. Attending to this essential and yet strangely neglected issue, Baras argues that if calling for explanation is thought of as a fixed property of facts that justifies explanatory inferences, as many believe it to be, this leads to a futile philosophical project and confusions in reasoning. He develops the view that calling for explanation is merely a figurative form of speech without a fixed meaning. There is no unified property shared by all facts that call for explanation, and there is no unified kind of explanation that all such facts call for.