Theoreticians associated with different schools of thought have been participating in spirited exchanges about the nature of membership in society for more than a century. Theory users cannot afford disciplinary chauvinism but must borrow from many of these traditions. Theories for Practice crosses disciplinary boundaries and draws from psychology, sociology, economics, biology, the cognitive sciences and other disciplines as they contribute to the practical understanding of social membership processes. It provides social workers, applied sociologists, and other human service professionals with practical tools for developing fluency in many theoretical languages.