This chapter begins with a view and critique of Karl Popper (1940's and 1950's), a controversial critic of Marxian ideas (utopian social engineering), who favored “piecemeal social engineering” to reduce defined problems causing specific harms. Interventions would be tried to test whether the measures to deal with these harms were having their intended effects and not creating other harms. This social theory of Popper’s was criticized for challenging Marxian ideas. Also criticized was Popper’s “falsificationist” account of scientific development arguing that scientific theories are invented and must be falsifiable and rigorously tested. Then, in the late 1980's, through the Safer Cities program, funding opportunities for crime reduction research and evaluation became available and took part in the piecemeal social engineering advocated by Popper. Situational crime prevention was developed in the Home Office and was used by Safer Cities. However, situational crime prevention, like Popperian social science, elicited similar objections in its failure to address root problems leaving a flawed social structure untouched. Linking the ideas of realistic evaluation, piecemeal social engineering and situational crime prevention can offer a method and set of principles to guide decisionmaking to deal effectively with emerging harms and threats. The best claims of realistic evaluation, piecemeal social engineering, and situational crime prevention lie in their explanatory power and practical application for harm reduction which are contested. The hope is scientific discourses in shaping the criminological agenda will not be squeezed out with the involvement of politics in crime reduction. References