When Islamic State group militants invaded the Central Library of Mosul earlier this month, they were on a mission to destroy a familiar enemy: other people's ideas. Residents say the extremists smashed the locks that had protected the biggest repository of learning in the northern Iraq town, and loaded around 2,000 books — including children's stories, poetry, philosophy and tomes on sports, health, culture and science — into six pickup trucks. They left only Islamic texts. The rest? "These books promote infidelity and call for disobeying Allah. So they will be burned," a bearded militant in traditional Afghani two-piece clothing...