The concept of culture not only seemed to provide the definitive refutation of the notion of a universal human nature, but it appeared to be a refined tool for understanding group differences in behavior. Since human behavior is culturally determined, and since cultures vary enormously, the only valid generalization that can be made about human nature is that it is enormously malleable. The chapter argues that in the traditional conception, “culture” referred to all aspects of a group’s environment, except the physical, and to all aspects of man, except the biological. Culture determinist theories of behavior and of personality were developed in the first instance as alternatives to and refutations of biological determinism. In sum, when personality is viewed as a system with differentiated structures and functions, the simple isomorphism between culture, behavior, and personality postulated by the internalization-of-culture model is frequently found wanting.