Abstract
For the past half century, behavior therapy has served as the theoretical basis for successful inquiries into the nature and treatment of many emotional disorders. Although there are core principles shared by all behavior therapies, two primary approaches, traditional cognitive behavior therapy (CBT) and acceptance and commitment therapy (ACT), have emerged as the most viable treatment approaches, even though they achieve their success through different methods and are predicated in different assumptions, principles, questions, and scientific strategies. In this special series, theorists and therapists with allegiances to one of these two approaches articulate the philosophical and theoretical underpinnings of their approach, summarize the evidence to date, point out current gaps or inconsistencies, and map out future directions with predictions informed by theory. The series concludes with a capstone paper that seeks to find common ground within the family of behavior therapies while also positing ways for behavior therapy to remain relevant in a world that increasingly emphasizes neuroscience and biobehavioral approaches to understand and reduce human suffering.