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Special Issue: Psychology of Violent Extremism

The end of ideological violence

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Received: July 14, 2026. Accepted: July 16, 2026. Published: July 17, 2026. https://doi.org/10.56296/aip00066 · © 2026 The Author(s)

Author Details

: Department of Psychology, Bryn Mawr College

*Please address correspondence to Clark McCauley, cmccaule@brynmawr.edu, Psychology Department, Bryn Mawr College, 101 N. Merion Ave, Bryn Mawr. PA 19010, USA

Transparent Peer Review

This commentary was only editorially reviewed, in accordance with the journal policies for this publication format.

Abstract

Why does non-state violence without a clear ideology represent a problem for terrorism scholars? This comment on Horgan and Shayler, Perliger, Baele, and Cassam suggests that lone-actor perpetrators with no-or-mixed ideology are the beginning of the end of defining terrorists and violent extremist as ideologically motivated. An alternative is available that does not privilege broad conceptions of ideology. The role of ideas in radicalization to terrorism and violent extremism is better understood in terms of the three dimensions of a mobilization frame: diagnostic, prognostic, and motivational framing.
Editor Curated

Key Takeaways

  • The commentary argues that a growing number of lone-actor attackers—overwhelmingly young men—commit mass violence with no clear or consistent ideology, which challenges the long-standing definition of terrorism and violent extremism as 'ideologically-motivated' violence. This makes 'salad bar' (mixed-ideology) and nihilistic cases hard to fit into traditional research categories.
  • McCauley proposes replacing ideology with the concept of 'collective action framing' drawn from Social Movement Theory, which uses three dimensions: diagnostic (identifying the grievance or blame), prognostic (the proposed violent solution), and motivational (who should act). This framework applies to both attackers and their targets and to all official FBI/DHS categories of violent extremism.
  • The author identifies four problems with relying on ideology: there is no agreed definition, no reliable way to measure it, an over-focus on 'bad ideas' that ignores emotions like anger and humiliation, and a tendency to locate the problem only 'in their heads' rather than in the interaction between conflicting groups. Nihilistic Violent Extremism, driven by fascination with violence rather than grievance, is treated as a genuine exception even to this action-frame approach.
Keywords:

Introduction

These four papers offer different interpretations of the recent increase in lone-actor perpetrators of violence who do not fit easily into the usual categories of political violence (jihadist, right-wing, left-wing). Horgan and Shayler (2026) are worried that ‘salad bar’ combinations of ideologies justifying violence are too many and too fuzzy to make useful research categories; they offer a taxonomy for making sense of such combinations. Perliger (2026) is worried that research is not digging deep enough into the intellectual roots of extremist ideologies to see the continuities in recent perpetrators. Baele (2026) is worried that new kinds of extremist violence are emerging that are not connected with old categories of ideology. And Cassam (2026) joins Baele (2026) in worrying about non-ideological violence, arguing that a proper definition of ideology leaves some recent lone-actor violence with no connection to ideology.

In this comment I try to show that, despite their differences, the first three papers show an attachment to the power of ideology that gets in the way of understanding recent examples of non-ideological attacks. I join Cassam (2026) in focusing on non-ideological violence and its implications for the category of violent extremist, then offer suggestions for replacing ideology with action frame in studying the role of ideas in lone-actor violence.

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Why Is Non-ideological Violence a Problem?

All four papers start from the same problem: how to understand perpetrators of violence who show no-or-mixed ideology? Most of these perpetrators are lone actors. Why should scholars of terrorism find it a problem that there are individuals who kill for reasons that have nothing to do with ideology?

Terrorism is a form of intergroup conflict, in particular a form of asymmetric conflict in which terrorism is the ‘warfare of the weak.’ (There is another form of asymmetric conflict in which the state makes war on a minority—terrorism from above or politicide—that does not need to be unpacked for this discussion.) No doubt there are individuals who kill for reasons that have nothing to do with intergroup conflict. These individuals are studied by criminologists, but why are they a problem for terrorism scholars?

To be fair, all four papers talk more about violent extremism than about terrorism. Surprisingly, none of the first three papers tries to define violent extremism. Cassam (2026, p. 2) defines it in a question: “…how can there be an extremist for whom ideology is not relevant, given the assumption that a defining characteristic of extremism properly so called is that, like terrorism, it is ideologically motivated?”

The U.S. Government (The White House, 2011, p.1) first defined violent extremists as “individuals who support or commit ideologically-motivated violence to further political ends.” Later government definitions were even broader: “…individual who seeks to further political or social goals, wholly or in part, by unlawful acts of force or violence dangerous to human life (FBI/DHS, 2023, p. 3). The extremism of violent extremism is thus an extremism of ideas, understood as an extreme version of a political or social ideology.

Since 2018, the Federal Bureau of Investigation and the Department of Homeland Security have used five categories of violent extremism (FBI/DHS, 2023, pp. 4-5):

“Ethnically Motivated Violent Extremism: This threat encompasses the potentially unlawful use or threat of force or violence in furtherance of ideological agendas derived from bias, often related to race or ethnicity, …

Anti-Government or Anti-Authority Violent Extremism: This threat encompasses the potentially unlawful use or threat of force or violence in furtherance of ideological agendas, derived from anti-government or anti-authority sentiment, including opposition to perceived economic, social, or racial hierarchies, or perceived government overreach, negligence, or illegitimacy.

Animal Rights/Environmental Violent Extremism: This threat encompasses the potentially unlawful use or threat of force or violence in furtherance of ideological agendas by those seeking to end or mitigate perceived cruelty, harm, or exploitation of animals and/or the perceived exploitation or destruction of natural resources and the environment.

Abortion-Related Violent Extremism: This threat encompasses the potentially unlawful use or threat of force or violence in furtherance of ideological agendas relating to abortion, including individuals who advocate for violence in support of either pro-life or pro-choice beliefs.

All Other Domestic Terrorism Threats: This threat category encompasses threats involving the potentially unlawful use or threat of force or violence, in violation of federal law, in furtherance of political and/or social agendas which are not otherwise exclusively defined under one of the other threat categories. Such agendas may derive from, but are not limited to, a mixture of personal grievances and beliefs, political concerns, and aspects of conspiracy theories, including those described in the other DT [Domestic Terrorism] threat categories. Some actors in this category may also carry bias related to religion, gender, or sexual orientation. Several DVEs [Domestic Violent Extremists] have combined components of different ideologies to develop a personalized belief system that they use to justify violent, criminal action.”

So why not put ‘salad bar’ extremism in the All Other category? ‘Salad-bar’ extremists indeed combine “components of different ideologies to develop a personalized belief system that they use to justify violent, criminal action.” Horgan and Shayler (2026) also mention Nihilistic Violent Extremism (NVE) as part of the no-or-mixed ideology problem. Putting NVE under All Other looks easier since the government charged NVE-accused Baron Martin with terrorism (Baumgartner & Jonas, 2025).

Trying to Save Ideology

Some clues to why not All Other emerge in the first three papers. From Horgan and Shayler (2026, p. 11): “After all, a defining characteristic of terrorism is that it is ideologically motivated violence.” From Perliger (2026, p. 1): “But why has a field that spent five decades constructing increasingly refined models of ideological mobilization become so willing to conclude that ideology itself is receding?” And from Baele (2026, p. 4): “Second, the UK and US examples evoked above, together with multiple similar observations, encourage us to consider ‘MUU’-type [Mixed Unclear and Unstable ideologies] violence as a subset of a much larger interest in committing mass fatality attacks, rather than a form of ‘terrorism’ or even ‘extremism’. (…) What we face is a pool of young people (overwhelmingly men) captivated and attracted by extreme violence and keen to join the list of mass crime offenders…”.

These quotations begin to make clear what is at stake in the name given to perpetrators of violence who do not fit into the usual categories of ideology. Decades of research have assumed that non-state political violence can be understood in terms of ideology—one or another set of bad ideas. Now we are looking at cases of non-state violence, including mass-casualty violence, mostly by lone-actors, that cannot be connected to one ideology, or sometimes to any ideology. The first three papers find a way to react to this news without giving up on terrorism as ideologically-motivated violence.

One way is to doubt that the new cases are so different, and to suggest that study of ideological combinations can make sense of what appears at first a mishmash (Horgan & Shayler, 2026). A second is to double down on doubt that the new cases are really different by assuming that serious scholarship can find a thread of consistency in the mishmash (Perliger, 2026). The third is to frankly admit that the new cases are a new problem, something different from terrorism or extremism (Baele, 2026).

The first two reactions, doubting how much is new or assuming a hidden ideological consistency, cannot comprehend the cases where there is no sign of ideology in the perpetrator (Cassam, 2026). The third reaction can comprehend such cases but raises doubt that terrorism scholars have expertise relevant to understanding or responding to the new cases of violence.

There is another issue to be raised regarding ideology. Horgan and Shayler (2026) agree with Perliger (2026) that ideology is not the same as motivation. Individuals can join a militant or terrorist group for many reasons—status, friendship, escape, thrill-seeking—and may only later come to join in the group’s official ideology.

They also agree in suggesting that groups can be motivated by ideology even if individual members are not. “It can be very tempting to consider ideology a general proxy for motivation, and per our earlier points, even more tempting to invoke this at an organization or movement level as opposed to the individual level” (Horgan & Shayler, 2026, p. 14). “Ideology rarely operates as a private psychological engine. It operates as a collective framework that defines enemies, selects targets, legitimizes tactics, and supplies the narrative within which personal grievances acquire political meaning” (Perliger, p. 3).

A concern here is that it is not clear why individuals are more subject than groups and organizations to personal and emotional interests outside of ideology. If we think back to U.S. reactions to the 9/11 attacks, it seems clear that feelings of anger and humiliation dominated ideology in a rush for revenge that took the U.S. to Afghanistan and Iraq.

Returning to my earlier question, why not put both ‘salad-bar’ combinations of ideology and Nihilistic Violent Extremism into the All Other category of Violent Extremism? There must be something difficult or dangerous about putting new forms of lone-actor violence into this category.

What is different about this category is that it does not refer to ideology. The first four categories refer to “…use or threat of force or violence in furtherance of ideological agendas relating to …” (FBI/DHS, 2023, pp. 4-5). The fifth, All Other, category instead refers to “use or threat of force or violence…in furtherance of political and/or social agendas which are not otherwise exclusively defined under one of the other threat categories. Such agendas may derive from, but are not limited to, a mixture of personal grievances and beliefs, political concerns, and aspects of conspiracy theories, including those described in the other DT threat categories” (FBI/DHS, 2023, pp. 4-5).

The All Other category of violent extremism replaces reference to ideology with reference to social agendas. If ideology is only one possible contribution to a violent agenda, it is only one possible contribution to violent extremism. “As increasing numbers of individuals – mainly young men – engage in extreme violence for its own sake or in pursuit of pseudo-causes, the standard conception of extremism as fundamentally ideological will come under greater pressure” (Cassam, 2026, p. 5).

For some scholars and for some government officials, the danger is more far-reaching: the new cases of violence challenge the definition of terrorism as ideologically-motivated violence. If ideology is only one possible contribution to a violent agenda, perhaps ideology is only one possible contribution to terrorism. Ideology then may be a part of understanding terrorism, but not part of the definition of terrorism.

An Alternative to Ideology

There is a way of understanding terrorism and violent extremism that does not depend on privileging the role of ideology. This way begins with seeing terrorism and violent extremism as expressions of intergroup conflict. To understand group conflict we have to study both sides. For terrorism this means studying both the terrorists and their targets: the perceived threats, emotions, and actions of both sides. Similarly for violent extremism, this means studying both the extremists and their targets: the perceived threats, emotions, and actions of both sides. For both terrorists and violent extremists, it is the interaction of the two sides over time that is the focus.

Ideology can play a part but not a big part in understanding the interaction, for four reasons (McCauley, 2024; McCauley, 2025). First there is no agreement about the definition of ideology. For some it is reduced to one or more attitudes (liberal vs. conservative, Democrat vs. Republican); for others it is as broad as culture, so that even music (a nasheed) can be a part of ideology.

Second, and relatedly, there is no agreement about how to measure ideology. Everyone agrees that ideology is not static, that it develops and changes in response to real world events. But we have no polls tracking change in political ideology over time, unless we are ready to reduce ideology to something like a mark on a seven-point liberal-conservative scale.

Terrorism research, and four of the five categories of violent extremism, are thus in the uncomfortable position of defining the problem in relation to a concept—ideology—that is seldom measured.

Third, trying to understand terrorists and violent extremists as motivated by ideology puts the focus on cognition—bad ideas—and takes attention away from emotions. Interviews with terrorists and violent extremists find these individuals awash in emotions—fear, anger, shame, humiliation (McCauley, 2017). Terrorist targets, and the targets of violent extremists, are also swept up in emotions: Think of the U.S. after the 9/11 attacks, or Jewish Americans after the Pittsburgh synagogue shooting in 2018.

Fourth, trying to understand terrorism and violent extremism as motivated by ideology puts the problem out there, in their heads. The interactions of group conflict become invisible as we study only them, their bad ideas and how to combat these ideas.

Fortunately, there is a way to think about group conflict that does not depend on conceptions of ideology (McCauley, 2024; McCauley, 2025). Along with political opportunity and resource mobilization, collective action framing is a basic concept of Social Movement Theory (SMT; Wilson, 1973). SMT aims to understand how individuals come together in social movement organizations (SMOs) to work for social change.

A collective action frame is usually considered to have three dimensions. The diagnostic dimension identifies a problem or injustice, and who or what is to blame (in psychology and political science often called grievance). The prognostic dimension is a proposed solution to the problem—what needs to be done to make things right. And the motivational dimension identifies who should feel responsible to act, including rewards for action and a grand vision of the world to be achieved by successful action.

The three dimensions are general enough to apply to both sides of an intergroup conflict, including the conflict between terrorists and their targets. For a government and its citizens, the diagnostic framing claims that terrorists are guilty of unprovoked attack. The prognostic framing is often a war on terrorists that includes new powers for police, military, and intelligence agencies. The motivational framing emphasizes patriotic appeals to defend the nation and its values. McCauley (2024) provides examples of measuring the three dimensions with questions appropriate for polling research with terrorist sympathizers and terrorist targets.

The three dimensions are also general enough to apply to violent extremists and their targets. The diagnostic dimension (grievance) for Ethnically Motivated Violent Extremism is an ethnicity or race or religion seen as threatening or victimizing. For Anti-Government Violent Extremism, a grievance against the government or police is held by anarchists, militias, and ’sovereign citizens.’ For Animal Rights/Environmental Violent Extremism, the grievance is perceived harm to animals or environment. For Abortion-Related Violent Extremism, the grievance is against pro-life or pro-choice opponents. For All Other Domestic Terrorism Threats, the grievance can include many different kinds of perceived injustice, including personal injustice (school shooters), personal and group injustice (incels), and political injustice (assassins).

To threaten as violent extremists, individuals must have a prognostic frame that justifies violence and personal motivation to move to violence. For lone-actors, there may be two sources of such prognostic-motivational frames (McCauley & Moskalenko, 2014). Some individuals feel the suffering of others so strongly that they feel a personal responsibility to defend or revenge the perceived victims (caring compelled). Some individuals are social loners, often with mental health issues, who have a grievance and weapons experience; their turn to violence is an escape from unhappy life experience (disconnected disordered).

This perspective leaves one kind of violent extremist unaccounted for: Nihilistic Violent Extremists (NVEs) seem to have no grievance. Rather they are fascinated by violence and violent heroes; they are attracted to violence and the arousal value of thinking about, seeing, and participating in violence. I agree with Baele (2026) that this is something different, not to be understood as “grievance-fueled violence” (McCauley et al., 2013).

With this exception, the three dimensions of collective action framing are well able to describe the role of ideas for both terrorists and violent extremists. The three dimensions were originally suggested by John Wilson in his 1973 text, Introduction to Social Movements, in an effort to clarify and specify the role of ideology in the development of social movements. It appears that collective action framing may be a useful alternative to more abstract conceptions of ideology for understanding the role of ideas in radicalization to terrorism and violent extremism.

Conflicts of Interest

The author declares no competing interests.

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Frequently Asked Questions

  • What is 'non-ideological violence' and why is it a problem for researchers?

    Non-ideological violence refers to attacks—often by lone actors—committed for reasons that have little or nothing to do with a recognizable political ideology such as jihadism, right-wing, or left-wing extremism. As McCauley (2026) explains, this is a problem because terrorism and violent extremism have traditionally been defined as ideologically-motivated violence. When perpetrators show no clear ideology, or a personalized ‘salad bar’ mixture of ideas, scholars struggle to fit them into existing categories. The commentary notes that individuals who kill for purely personal reasons are usually studied by criminologists, so the rise of ideology-free mass violence forces terrorism researchers to question whether ideology should remain part of the very definition of their field.

  • What alternative to ideology does the author propose?

    According to McCauley (2026), the role of ideas in violence can be better understood through collective action framing, a core concept of Social Movement Theory first outlined by John Wilson in 1973. A collective action frame has three dimensions:

    1. Diagnostic – identifying the problem, injustice, or who is to blame (a grievance).
    2. Prognostic – proposing a solution, which for extremists justifies violence.
    3. Motivational – identifying who should feel responsible to act, plus the rewards and vision driving them.

    McCauley argues these dimensions apply to both attackers and their targets, capturing the interaction between conflicting groups over time rather than treating ideology as a private ‘engine’ inside one side’s head.

  • Why does McCauley (2026) say ideology is unreliable for studying terrorism?

    McCauley (2026) offers four reasons for demoting ideology from its central place in terrorism research. First, there is no agreed definition—some reduce it to a single attitude while others stretch it as broadly as culture. Second, and relatedly, there is no reliable way to measure it, since ideology constantly changes with real-world events yet is rarely tracked in polls. Third, focusing on ideology emphasizes cognition and ‘bad ideas’ while ignoring the powerful emotions—fear, anger, shame, humiliation—that interviews with extremists repeatedly reveal. Fourth, it places the problem entirely ‘in their heads,’ rendering the two-sided interaction of group conflict invisible. Together these limitations, he argues, make action frames a more practical foundation.

  • What is Nihilistic Violent Extremism, and how does it fit the framework?

    Nihilistic Violent Extremism (NVE) describes perpetrators who appear to have no grievance at all but are instead fascinated by violence and violent heroes, drawn to the arousal value of imagining, witnessing, and committing violence. McCauley (2026) notes that the U.S. government has already prosecuted an NVE-accused individual under terrorism charges. Importantly, McCauley treats NVE as a genuine exception even to his own action-frame model, because the framework depends on a diagnostic ‘grievance’ dimension that NVE cases lack. He agrees with Baele (2026) that this represents something distinct and should not be understood as ‘grievance-fueled violence.’ For every other category, however, the three action-frame dimensions apply well.

References

Baele, S. (2026). Why the ‘salad bar’ might actually help extremism research – A reply to Horgan and Shayler. advances.in/psychology, 1, e359159. https://doi.org/10.56296/aip00060

Baumgartner, L., & Jonas, B. (2025). How the DOJ is prosecuting Nihilistic Violent Extremism as Domestic Terrorism. Just Security, December 25. https://www.justsecurity.org/126226/prosecuting-nihilistic-violent-extremism-domestic-terrorism/

Cassam, Q. (2026). Extremism without ideology. advances.in/psychology, 1, e945134. https://doi.org/10.56296/aip00062

FBI/DHS. (2023). Strategic Intelligence Assessment and Data on Domestic Terrorism. https://www.dhs.gov/sites/default/files/2023-07/23_0724_opa_strategic-intelligence-assessment-data-domestic-terrorism.pdf

Horgan, J., & Shayler, M. (2026). Why the ‘salad bar of ideologies’ does not help us understand contemporary violent extremism. advances.in/psychology, 1, e607682. https://doi.org/10.56296/aip00057

McCauley, C., Moskalenko, S., & Van Son, B. (2013). Characteristics of lone-wolf violent offenders: A comparison of assassins and school attackers. Perspectives on Terrorism, 7(1), 4-24. https://pt.icct.nl/article/characteristics-lone-wolf-violent-offenders-comparison-assassins-and-school-attackers

McCauley, C., & Moskalenko, S. (2014). Toward a profile of lone wolf terrorists: What moves an individual from radical opinion to radical action. Terrorism and Political Violence, 26(1), 69-85. 

https://doi.org/10.1080/09546553.2014.849916
McCauley, C. (2017). Toward a psychology of humiliation in asymmetric conflict. American Psychologist, 72(3), 255-265. https://doi.org/10.1037/amp0000063

McCauley, C. (2024). Research Note: The role of ideas in radicalization to terrorism: Ideology and narrative vs. diagnostic, prognostic, and motivational action frames. Journal for Deradicalization, 38, 211–37. https://journals.sfu.ca/jd/index.php/jd/article/view/869

McCauley, C. (2025). Can we leave ideology behind? Diagnostic, prognostic, and motivational action frames in tracking radicalisation and deradicalisation. Perspectives on Terrorism, XIX(4). https://doi.org/10.19165/ntzz3710 

Perliger, A. (2026). The erosion of conceptual clarity in the study of political violence. advances.in/psychology, 1, e824472. https://doi.org/10.56296/aip00059

The White House. (2011). Empowering Local Partners to Prevent Violent Extremism in the United States. https://obammawhitehouse.archives.gov/sites/default/files/empowering_local_partners

Wilson, J. (1973). Introduction to social movements. New York: Basic Books. https://doi.org/10.1093/sf/53.1.146 

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