Presented by Jane Hathaway, Professor of History at The Ohio State University, to the Clio Society on April 18, 2016. This talk addresses the historical origins of key “radical” -- or, more appropriately, puritanical or revivalist -- movements in Sunni Islam. The focus is on two main strands of Sunni revivalism: Wahhabism, which originated in the mid-18th century, and the Muslim Brotherhood, which originated in the early 20th century. Both these tendencies seek to root out innovations to the practice of the original Muslim community in the 7th century, but what they regard as innovations and the ways in which they attempt to eradicate them vary widely. Discussion includes a number of groups and movements that have been in the news in recent years, including Hamas, al-Qaeda, and ISIS.