Radicalization can be defined as a particular repertoire of collective action that involves deliberate infliction or threat of infliction of physical injury or damage for political ends, considered at that time as illegitimate in the dominant culture. Discussed later in this article is how even lone wolf terrorism should be considered part of a collective social process. People can radicalize [Page 684]along two different routes: through participation in radical (or extreme) political parties or through participation in radical social movements.

In addition to a focus on the action repertoire, radicalization can also be considered as a process. Scholars depict the process of radicalization as a staircase. People are located on different floors of the building, but everyone begins on the ground floor. Thought and action on ...