Abstract Max Weber and Ludwig von Mises were two of the 20th century's foremost theorists of human action. Mises held Weber, his senior by some 17 years, in great esteem and often discussed his theories, even weaving some, such as Weber's model of ideal types, deeply into the fabric of his own social thought. However, at least at first glance, there seems to be a deep rift between the two men's conceptions about the rationality of action. Weber classified “social actions” into several distinct categories, some of which he saw as exhibiting little, if any, rationality. Mises, in contrast, held that all action is rational by conceptual necessity. Various writers have taken their views to be obviously incompatible, among them, Mises himself. This article suggests that the appearance of a conflict is produced by the failure to discern that Weber and Mises were addressing different sorts of questions and constructing frameworks to support different modes of analyzing social phenomena. I contend that, if that divergence of aim is properly understood, then the apparent contradiction will be seen as illusory.