Despite the historical continuity of street gangs, each new generation tends to perceive the street gang as a new phenomenon generated by particular contemporary conditions and destined to vanish as these conditions vanish. The subtle and intricately contrived relations among cliques, leadership, and crime reveal the gang as an ordered and adaptive form of association, and its members as able and rational human beings. The gang serves the lower-class adolescent as a flexible and adaptable training instrument for imparting vital knowledge concerning the value of individual competence, the appropriate limits of law-violating behavior, the uses and abuses of authority, and the skills of interpersonal relations. The main reason that people have consistently mistaken the prevalence of gangs is the widespread tendency to define them as gangs on the basis of the presence or absence of one or two characteristics that are thought to be essential to the "true" gang. For many people there are no gangs if there is no gang warfare. Evidence indicates that the core characteristics of the gang vary continuously from place to place and from time to time without negating the existence of the gang.