Paul E Walker is a historian of ideas with special interests in Fatimid history and Ismaili thought. He is currently a research associate in the Department of Near Eastern Languages and Civilizations at the University of Chicago. His previous books include "Early Philosophical Shiism" (1993), "Exploring an Islamic Empire: Fatimid History and Its Sources" (2002), and with Wilferd Madelung, "The Advent of the Fatimids: A Contemporary Shi'i Witness "(2000).