Sometime in the middle of the first century AD, a slave named Epictetus was born in Hierapolis, a city in what is now southwestern Turkey. He was the property of a man named Epaphroditus, a freedman who had himself risen to become a secretary to the emperor Nero. At some point during his enslavement, Epictetus suffered a permanent injury to his leg that left him with a lifelong limp. These biographical facts are among the few that can be stated with confidence about the early years of a man who would become one of the most influential philosophical teachers of...