First, a delinquent must be detected early in his/her criminal career; this requires efficient policing that targets where crime is occurring. Second, the delinquent youth must be punished quickly and efficiently. This means limiting his freedom and autonomy, either for part of his/her time under the supervision of the probation service or for all the time in prison. The severity of the punishment is far less important than its certainty and speed. Third, while the offender is being punished, he/she must be trained in the virtues essential to law-abiding behavior. This means offering the offender the opportunity of joint activity with others, of learning a real skill or social joint practice. Giving a youth the experience of having to learn a skill from and with others develops virtue. Finally, when due punishment is over, every effort must be made to usher the youth into some positive social grouping where he/she can be guided into lawful ways of doing useful activities with others. Preventing delinquent behavior in the first place requires, at a minimum, setting up programs in inner cities so that youth have something to do and learn joint skill from others that develop virtue.