In 1978 Barbara Pillsbury and I dedicated our coedited book, Muslim–Christian Conflicts: Economic, Political and Social Origins (Westview), with these words: “To those who struggle to demystify religion and to those who suffer and die because the struggle is yet unfinished.” Charles Issawi observes in his preface that the contributors to the volume tend to interpret the conflicts more in economic and political terms than in “religious” terms. In an effort to develop analytical tools, my introduction distinguishes between “religion/religious identity and consciousness” (as theology/theological consciousness) and “sect/sectarianism” (as social organization, relationships, dynamics/group identity, and consciousness). I argue that sectarianism is about how “differences” are constructed; because people can believe they are very different when they are not, the task of the scholar is to describe what differences do exist, how they emerged, and why people believe they are different. Differentiation is a process, I suggest, that operates through the everyday—through socialization, through family systems, and through various other aspects of social organization in both systematic and erratic or contradictory ways.