Chapter 2 discusses the contested meanings of the umma, specifically in Sunni thought. It reviews the ways the concept is understood as having a classical reference point in the era of the Prophet and his immediate successors, and follows its development through medieval and modern scholars. A consistent theme has been that the community of the faith must be tied to proper leadership, but the declining and then dismissed Caliphate in the second decade of the twentieth century, stirred intellectual and political agitation. Today calls for unity, or at least solidarity, contend with debates over how extensive the umma is and how much difference is allowable within it. The chapter argues that the aspiration to both comprehensiveness and internal tolerance is commonly reaffirmed, yet challenged by normative ambivalence within the concept itself.