PROLOGUE: HOW DO WE KNOW WHEN WE ARE ON TO SOMETHING? 1 Albert I. Baumgarten The invitation to the conference whose papers are gathered in this vol- ume noted the problems of different sorts associated with the notions of “sects” and “sectarianism.” In light of these difculties, the par- ticipants were invited to address a series of questions concerning the application of these ideas to a range of moments in Jewish experience, from antiquity to contemporary times. In framing the issues this way, the conference organizers expressed an on-going hesitation by scholars in Jewish Studies concerning the applicability of notions of “sects” and “sectarianism” in their eld, despite decades in which the hitching of the social sciences to historiography has become more and more widely accepted and its value recognized. Not surprisingly, many of the papers presented at the conference, reected in the written ver- sions collected in this volume, are examples of what anthropologists call the phenomenon of “not in my tribe.” That is, after one scholar presents his or her ethnographic study and suggests the potential wider signicance of these results, someone in the audience objects loudly by saying that perhaps the conclusions just proposed may be valid for the tribe studied by the scholar in question, but “not in my tribe.” 2 “Sects” and “sectarianism,” any number of our colleagues proclaim, might be helpful notions in various corners of Jewish history, usually far from their own, but not that useful, for differing reasons, for the specic material they study. The problematic status of the notions of “sects” and “sectarianism” across the spectrum of those who study the Jewish past raises the bar of proof even higher than usual for those scholars who elect to utilize 1 In this written version, to the fullest extent possible, I preserve the oral style, character, and rhetoric of the presentation at the conference. 2 For one example, note Gellner’s comment that the Weberian distinction between sect and church would look completely different, inside out, if the examples taken to dene the paradigm were the cases he studied in North Africa: E. Gellner, Saints of the Atlas (London and Chicago, 1969) 11.