In this article I want to ask what we should do, either collectively or individually, if we could identify by genetic and family profding the 12% of the male population likely to commit almost half the violent crime in our society. What if we could identify some individuals in that 12% not only at birth, but in utero, or before implantation? I will explain the source of these figures later; for now, I will use them only to provide a concrete (...) example of the kind of predictive claims we can expect to be made with some frequency, and some scientific credibility, over the next generation. I will adopt an outlook that one commentator has called “pragmatic optimism,” but which could also be called technological optimism - the belief that a science or technology will achieve many or most of its advertised goals. My optimism will be directed towards human behavioral genetics, the source of predictions like the one I just offered; I will assume that this controversial discipline will achieve a substantial pan of its scientific ambition to identlfy genetic differences among individuals that help predict and possibly explain future behavior, psychological health, and cognitive skill. This optimism is very limited -it concerns the scientific success of behavioral genetics, not the social value of that success. (shrink)