The Introduction examines the academic history of the study of sectarianism among Western sociologists, concluding that the categories established by Weber and his students are not overly helpful in understanding the history of the Muslim firaq. It outlines a new methodology for their study: the narrative-identity approach, which posits that human beings emplot themselves in narratives in order to find meaning and orient themselves, and that sect narratives are some of the narratives that human beings might choose to emplot themselves within. This methodology focuses more on what sectarian actors do, and treats the grand sect narratives as narratives of salvation that offer meaning to those emplotted. It then moves to the sources of Muslim sect narratives, paying particular attention to the problematic genre of heresiography. It ends with a brief discussion of the structure of the work.