Behavior therapy is an increasingly complex approach to the treatment of human problems, ballooning in the last fifty years to nearly one hundred separate techniques. In this book, leading researchers and clinicians identify the fourteen core principles behind the 400 separate treatment protocols and summarize the theory behind, history of, evidence base, and applications of these core principles of cognitive behavior therapy as they relate to current practice. Students and practitioners will benefit from the perfect balance of history, theory, and evidence base with guidance for real world applications.