The term “terror” is chiefly used in reference to two political practices. The first is an instrument or form of government under which violent repression is used to discipline a people faced with political emergency, to purify them of moral corruption, or both. This usage emerged in the rhetoric of the Jacobin regime in revolutionary France and has occurred since in characterizing the violent politics of the “totalitarian” regimes of the twentieth century. A related but distinct usage emerging since has seen “terror” and more commonly “terrorism” describing (and typically being used to denounce) certain “small war” tactics, especially when used by nonstate groups pursuing political aims such as national liberation or social revolution (though it also encompasses groups on the political right along with those committed to religiously inspired ideology). Moral and political philosophers differ widely on precisely which types or aspects of political violence merit this usually pejorative label and on the specific features that distinguish it from other kinds of wrong. Rival approaches emphasize, respectively, the injustice of the cause that terrorists pursue, the indiscriminate nature of their violence, their use of fear to coerce third parties, and their lack of authority to use force. Moreover, the use of terrorism by those struggling against regimes widely regarded as unjust has led some theorists to ask whether it might not sometimes be justified, with some arguing that it can.