In scarcely a century, Salafism has transformed Sunni Islam. Claiming to be a revival of the purest form of Islam, this movement promotes ultraconservative social and religious norms and rejects all non-Sunni religious groups. In Egypt, its influence has grown to the point of reshaping mainstream conceptions of the faith. How did such a deep religious transformation sweep through Egypt so rapidly? What is the significance of Salafism for the country's...