  This debate, like almost every debate in criminology, lacks microfoundations. It would certainly be nice to know what is going through people’s mind when they commit crimes, and thus how likely various measures are to change their behavior, but the fact is we do not know. Indeed, there is considerable skepticism among criminologists that a “general theory” of crime is possible. Nevertheless, we can easily imagine criminologists deciding that one particular factor, such as a demographic shift in the population (i.e., fewer young men), is the explanation for the late-20th century decline in violent crime in the United States, and ruling out the other hypotheses. And even though this may be a “half-way” explanation, there is no question that it would represent a genuine discovery, one that we could learn something important from.