Vigilantes have arisen at many times in different regions of the world, taking the law into their own hands as defenders, often by force, of their view of the good life against those they see to be its enemies. They have a strong attraction for some commentators and they rouse equally strong hostility in others. For yet others, who attempt to take a broader view, they are a source of deep ambivalence. Academic interest in the phenomenon has grown strongly over recent years, and this has contributed significantly to an increase in knowledge of its distribution beyond the bounds of western Europe, the United States, and particularly in many parts of Africa. Although vigilantes are most commonly male, increased evidence of women’s vigilantism has also come to light in recent years.
Vigilantism is difficult to define in rigorous terms, partly because of general problems of comparative study, but there are also special reasons in this case. Vigilantism is not so much a thing in itself as a fundamentally relational phenomenon which only makes sense in relation to the formal institutions of the state. It is in several ways a frontier phenomenon, occupying an awkward borderland between law and illegality. Many of its manifestations are short-lived and unstable, nor is it always what it claims to be. For these reasons, definitions of vigilantism are best treated as an “ideal type,” which real cases may be expected to approximate to or depart from. This approach provides the possibility of comparing different cases of vigilantism and also allows one to explore the differences and similarities between it and other “dwellers in the twilight zone,” such as social bandits, mafias, guerrillas, and resistance movements.