When President Barack Obama visited Cairo in 2009 to deliver an address to Muslims worldwide, he followed in the footsteps of countless politicians who have taken the existence of a unified global Muslim community for granted. But as Cemil Aydin explains in this provocative history, it is a misconception to think that the world's 1.5 billion Muslims constitute a single religio-political entity. How did this belief arise, and why is it so widespread?...