This article examines the concept of "brotherliness" as presented in Max Weber's sociological studies of religion. It argues that Weber presents a complex, if at times implicit, understanding of a number of contrasting forms of brotherliness: charismatic, Puritan, mystic, and medieval Christian. The article suggests that although these contrasting forms have been largely overlooked by Weberian scholars, they add an important dimension to Weber's understanding of the costs and paradoxes of Western rationalization.