Alternative images of how society develops and uses knowledge in confronting various social problems are sketched, and the different sketches are applied to analyze efforts to expand community policing and to prevent youth violence. A social research and development model is presented in which formal scientific inquiry establishes the size and character of problems nominated for social action, identifies problem causes, supports efforts to devise effective interventions, and disseminates findings and important innovations. The model is evaluated in terms of its strengths and weaknesses. Alternative models are proposed for solving social problems, and points of comparison among the models are noted. Application of the models to community policing and violence prevention is discussed. 41 references