This volume marks the culmination of the Fundamentalism Project , a series that brings together scholars from around the world to explore the nature and impact of fundamentalist movements in the 20th century. Based on an interdisciplinary programme conducted by the American Academy of Arts and Sciences, the series is dedicated to promoting an understanding of fundamentalism at a time when misinformation and misperceptions have exacerbated national and international conflicts. The four previous volumes provide information on the social, political, cultural and religious contexts of fundamentalism in the major religious traditions. In this fifth volume, the contributors return to, and test, the project’s beginning premise: that fundamentalisms in all faiths share certain family resemblances . Several of the essays reconsider the project’s original definition of fundamentalism as a reactive, absolutist and comprehensive mode of anti-secular religious activism. Some contributors challenge the idea that fundamentalism is a distinctively modern phenomenon, while others question whether the term fundamentalist can accurately be applied to movements outside Christianity, Judaism and Islam. Several of the essays also employ new approaches, drawn from literary criticism and from psychology, in their assessments of the problems of comparing fundamentalisms. This book concludes with a capstone statement by R. Scott Appleby, Emmanuel Sivan, and Gabriel Almond that builds upon the entire Fundamentalism Project. Identifying different categories of fundamentalist movements, and delineating four distinct patterns of fundamentalist behaviour toward outsiders, this statement provides an explanatory framework for understanding and comparing fundamentalisms around the world.