This book brings together the papers written by the authors over the last fifteen years on the historical and philosophical foundations of Albert Ellis' Rational Psychotherapy (later Rational Emotive Behavior Therapy, REBT) and its relationship to Stoicism, especially the later practical form represented by Epictetus. It goes beneath the well known similarities between Stoic "spiritual exercises" and modern psychotherapy, to look at the cause of these similarities. These lie in the conceptual continuities that connect the Stoics and other ancient philosophies with the modern cultural framework underlying psychotherapy.