Questions about the authenticity and authority of sunna have long been of central importance to the study of Islam, especially to those concerned with Islamic law. In this fascinating study, Daniel Brown traces the emergence of modern debates over sunna, focusing in particular on Egypt and Pakistan where these controversies have raged most fiercely, and assesses the implications of new approaches to the law on contemporary movements of Islamic revival. Using the case of modern Islam as a starting-point, the author considers how adherents of any great tradition deal with change.