In the first section, the author argues that it is not possible to fully distinguish between leading crime theories by focusing on the effect of independent variables because the theories share many of the same independent variables in common. In the second section, the author contends that leading crime theories are best distinguished in terms of their specification of crime motives. Such motives may be either positive or negative, and they explain why independent variables lead to crime. With certain exceptions, such motives have been neglected in empirical research. The nature of these motives is discussed, and suggestions for their measurement are offered. Consideration is paid to social control, self-control, strain, differential association, and social learning theories. 111 references and 9 notes