Born a slave, the Roman Stoic philosopher Epictetus (c. 55-135 AD) taught that mental freedom is supreme, since it can liberate one anywhere, even in a prison. In How to Be Free, A. A. Long-one of the world's leading authorities on Stoicism and a pioneer in its remarkable contemporary revival-provides a superb new edition of Epictetus's celebrated guide to the Stoic philosophy of life (the Ench…