Since no religious institution has emerged from Islamic religious history that is the sole and binding determinant of legitimate faith, Muslim scholars had to legitimize their religious positions in a different way. Canonisation and censorship processes, this volume argues, played a decisive role in the formation and deconstruction of religious authority. This volume therefore examines how texts, positions and the people behind them gain or lose their authority, and which structural, contextual and institutional factors contribute to the establishment or suppression, but also to the maintenance of this claim. Case studies from different historical periods and regions of the Islamic world show how certain religious beliefs gain legitimacy and others lose legitimacy in a specific historical context.