extremism
Definition
Extremism refers to positions or behaviours that fall near the outer end of a distribution of stances on violence, ideology, or related commitments, and which may or may not be grounded in a coherent belief system. A longstanding assumption in the field holds that extremism is ideologically motivated, yet this assumption is challenged by cases in which individuals are fixated on violence for its own sake rather than in service of any political, religious, or racial cause. A further category of concern involves actors who assemble fragments of multiple, sometimes contradictory ideological content, a pattern described as 'salad bar' extremism, where the primary interest is the violence itself and ideology functions chiefly to justify or rationalise it. The distinction between 'value extremists,' who regard violence as intrinsically good, and 'violence-fixated individuals' whose extremism carries no ideological content at all, demonstrates that existing taxonomies organised around ideological mixing or migration cannot account for the full range of violent actors. Empirical evidence on these categories remains limited, and there is an acknowledged need for greater conceptual clarity and terminological consistency across research and practice.
Sources: Cassam (2026), Horgan & Shayler (2026)
Applications
Extremism and Ideology
The relationship between extremism and ideology is contested rather than definitional. Some individuals present with multiple ideological commitments that they mix or migrate between, while others commit acts of violence with no identifiable ideological cause, as in the case of one individual whose extremism satisfied none of the four conditions proposed for a belief system to qualify as an ideology, those being subject matter, generality, interconnectedness, and explanatory ambition. A bare commitment to the value of violence lacks the generality, systematicity, and explanatory ambition that ideology requires, which means that ideological taxonomies cannot serve as a universal framework for classifying violent actors. Practitioners and researchers have proliferated terminology precisely because the relationship between ideology and violence is unstable and varies considerably across cases.
Sources: Cassam (2026), Horgan & Shayler (2026)
Extremism and Radicalization
Contemporary patterns of radicalization increasingly involve young people who lack formal ties to designated extremist organisations. Evidence suggests that rising case counts may partly reflect shifts in practitioner classification practices rather than a genuine surge in a new phenomenon. The diminishing influence of hierarchical organisations, combined with rapidly changing online ecosystems, has altered how radicalization proceeds and makes it harder to assign individuals to established ideological categories.
Sources: Horgan & Shayler (2026)
Extremism and Terrorism
Extremism and terrorism overlap but are not coextensive. Under UK law, a violent actor whose violence lacks any ideological purpose may be classified as an extremist while falling outside the legal definition of a terrorist, since a defining characteristic of terrorism is that it is ideologically motivated. The question of how much ideological commitment is required for an act to constitute terrorism remains unresolved, with evidence suggesting that for some actors ideology is the primary driver, while for others it is irrelevant or only a byproduct of sustained engagement with fellow travellers.
Sources: Cassam (2026)
