Abstract: In its ideal form, arbitrariness review is an instrument for promoting “deliberative democracy”—a system that combines reason-giving with political accountability. Under arbitrariness review in its current form, courts tend to embrace the “hard look doctrine,” which has a procedural component, requiring agencies to offer detailed justifications, and also a substantive component, in which courts assess the reasonableness of agencies’ choices on the merits. These are serious constraints on the executive branch, and they also reduce the risk of large-scale instability in government, in which scientific and economic judgments are overridden by political considerations. With respect to regulatory policy, it is not enough to say that “elections have consequences.”