Patricia Crone is Mellon Professor of Islamic History, School of Historical Studies, Institute of Advanced Study, Princeton. Her numerous publications include Slaves on Horses: The Evolution of the Islamic Polity (1980, 2003), God's Caliph: Religious Authority in the First Centuries of Islam, coauthored with Martin Hinds (1986, 2003), Pre-Industrial Societies: Anatomy of the Pre-Modern World (1989, 2003) and God's Rule: Government and Islam: Six Centuries of Medieval Islamic Political Thought (2005).