SUMMARY
In some schools of thought of radicalisation research there is a tacit assumption that individuals become gradually radicalised in their ideas, attitudes, political preferences and worldview, and then motivated by this subsequently radicalise their actions to commit an act of terrorism. This article supports those who question this linear model and I argue that these two processes, which are here labelled as ideological and behavioural radicalisation, must be differentiated. Drawing on ideas from radicalisation in genocide studies, this article contributes to the social movement theory approaches to terrorism. As such, the article differentiates between ideological and behavioural radicalisation processes and argues that these two types of radicalisation can be sequenced with either first. This article posits that it is possible for individuals to engage in radical actions without having extreme preferences, just as it is equally possible for other individuals to have radical ideologies without acting on them, supporting more social movement theory approaches to radicalisation. The article provides a plausibility probe for this sequencing, demonstrating its empirical utility for participation in genocidal violence.