This essay proposes to reframe the twentieth-century history of Islam by rethinking the relationship of that history to some dominant categories of twentieth-century sociology, especially the secularization thesis. The global history of Islam since the late nineteenth century has been shaped by an apparent paradox between its two most significant features. The first of these has consisted of persistent calls for Muslim revival, reform, and unity across the world, tending toward a unification or transcendence of the older forms of variation within the tradition. The second, countervailing tendency has been an increasing fragmentation of structures of authority within the tradition, a proliferation of the meanings attributed to it and of the forms of practice taken to embody it, and a renewed acuity of internal sectarian conflict. This is a paradox that only an understanding of Islam as social practice embedded in the forms of secularity characteristic of modern societies—and emphatically not one of Islam as “medievally” religious and uniquely “secularization-resistant”—can apprehend.