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)<\/a> are worried that \u2018salad bar\u2019 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)<\/a> 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)<\/a> is worried that new kinds of extremist violence are emerging that are not connected with old categories of ideology. And Cassam (2026)<\/a> 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.<\/p>\n\n\n\n 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<\/em> with action frame<\/em> in studying the role of ideas in lone-actor violence.<\/p>\n\n\n\n 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? <\/p>\n\n\n\n Terrorism is a form of intergroup conflict, in particular a form of asymmetric conflict in which terrorism is the \u2018warfare of the weak.\u2019 (There is another form of asymmetric conflict in which the state makes war on a minority\u2014terrorism from above<\/em> or politicide<\/em>\u2014that 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?<\/p>\n\n\n\n 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: \u201c\u2026how 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?\u201d<\/p>\n\n\n\n The U.S. Government (The White House, 2011, p.1) first defined violent extremists as \u201cindividuals who support or commit ideologically-motivated violence to further political ends.\u201d Later government definitions were even broader: \u201c\u2026individual 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.<\/p>\n\n\n\n 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): <\/p>\n\n\n\n “Ethnically Motivated Violent Extremism<\/em>: 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, \u2026<\/p>\n\n\n\n Anti-Government or Anti-Authority Violent Extremism<\/em>: 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. <\/p>\n\n\n\n Animal Rights\/Environmental Violent Extremism<\/em>: 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. <\/p>\n\n\n\n Abortion-Related Violent Extremism<\/em>: 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. <\/p>\n\n\n\n All Other Domestic Terrorism Threats<\/em>: 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.”<\/p>\n\n\n\n So why not put \u2018salad bar\u2019 extremism in the All Other<\/em> category? \u2018Salad-bar\u2019 extremists indeed combine \u201ccomponents of different ideologies to develop a personalized belief system that they use to justify violent, criminal action.\u201d Horgan and Shayler (2026) also mention Nihilistic Violent Extremism (NVE) as part of the no-or-mixed ideology problem. Putting NVE under All Other<\/em> looks easier since the government charged NVE-accused Baron Martin with terrorism (Baumgartner & Jonas, 2025).<\/p>\n\n\n\n <\/p>\n\n\n\n Some clues to why not All Other<\/em> emerge in the first three papers. From Horgan and Shayler (2026, p. 11): \u201cAfter all, a defining characteristic of terrorism is that it is ideologically motivated violence.\u201d From Perliger (2026, p. 1): \u201cBut 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?\u201d And from Baele (2026, p. 4): \u201cSecond, the UK and US examples evoked above, together with multiple similar observations, encourage us to consider \u2018MUU\u2019-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 \u2018terrorism\u2019 or even \u2018extremism\u2019. (\u2026) 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\u2026\u201d.<\/p>\n\n\n\n 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\u2014one 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. <\/p>\n\n\n\n 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). <\/p>\n\n\n\n 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. <\/p>\n\n\n\n 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\u2014status, friendship, escape, thrill-seeking\u2014and may only later come to join in the group\u2019s official ideology. <\/p>\n\n\n\n They also agree in suggesting that groups can be motivated by ideology even if individual members are not. \u201cIt 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\u201d (Horgan & Shayler, 2026, p. 14). \u201cIdeology 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\u201d (Perliger, p. 3).<\/p>\n\n\n\n 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.<\/p>\n\n\n\n Returning to my earlier question, why not put both \u2018salad-bar\u2019 combinations of ideology and Nihilistic Violent Extremism into the All Other<\/em> category of Violent Extremism? There must be something difficult or dangerous about putting new forms of lone-actor violence into this category. <\/p>\n\n\n\n What is different about this category is that it does not refer to ideology. The first four categories refer to \u201c\u2026use or threat of force or violence in furtherance of ideological agendas relating to \u2026\u201d (FBI\/DHS, 2023, pp. 4-5). The fifth, All Other,<\/em> category instead refers to \u201cuse or threat of force or violence\u2026in 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\u201d (FBI\/DHS, 2023, pp. 4-5).<\/p>\n\n\n\n The All Other <\/em>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. \u201cAs increasing numbers of individuals \u2013 mainly young men \u2013 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\u201d (Cassam, 2026, p. 5).<\/p>\n\n\n\n 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.<\/p>\n\n\n\n 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.<\/p>\n\n\n\n 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<\/em>) can be a part of ideology.<\/p>\n\n\n\n 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. <\/p>\n\n\n\n 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\u2014ideology\u2014that is seldom measured. <\/p>\n\n\n\n Third, trying to understand terrorists and violent extremists as motivated by ideology puts the focus on cognition\u2014bad ideas\u2014and takes attention away from emotions. Interviews with terrorists and violent extremists find these individuals awash in emotions\u2014fear, 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. <\/p>\n\n\n\n Fourth, trying to understand terrorism and violent extremism as motivated by ideology puts the problem out there<\/em>, in their<\/em> heads. The interactions of group conflict become invisible as we study only them, their bad ideas and how to combat these ideas.<\/p>\n\n\n\n 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<\/em> 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.<\/p>\n\n\n\n A collective action frame is usually considered to have three dimensions. The diagnostic <\/em>dimension identifies a problem or injustice, and who or what is to blame (in psychology and political science often called grievance<\/em>). The prognostic<\/em> dimension is a proposed solution to the problem\u2014what needs to be done to make things right. And the motivational<\/em> 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. <\/p>\n\n\n\n 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.<\/p>\n\n\n\n The three dimensions are also general enough to apply to violent extremists and their targets. The diagnostic dimension (grievance) for Ethnically Motivated Violent Extremism <\/em>is an ethnicity or race or religion seen as threatening or victimizing. For Anti-Government Violent Extremism, <\/em>a grievance against the government or police is held by anarchists, militias, and \u2019sovereign citizens.\u2019 For Animal Rights\/Environmental Violent Extremism<\/em>, the grievance is perceived harm to animals or environment. For Abortion-Related Violent Extremism, <\/em>the grievance is against pro-life or pro-choice opponents. For All Other Domestic Terrorism Threats, <\/em>the grievance can include many different kinds of perceived injustice, including personal injustice (school shooters), personal and group injustice (incels), and political injustice (assassins). <\/p>\n\n\n\n To threaten as violent <\/em>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<\/em>). 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<\/em>). <\/p>\n\n\n\n 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 \u201cgrievance-fueled violence\u201d (McCauley et al., 2013).<\/p>\n\n\n\n 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<\/em>, 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.<\/p>\n\n\n\n The author declares no competing interests.<\/p>\n\n\n\n\n\n\n Baele, S. (2026). Why the \u2018salad bar\u2019 might actually help extremism research \u2013 A reply to Horgan and Shayler. advances.in\/psychology, 1<\/em>, e359159. https:\/\/doi.org\/10.56296\/aip00060<\/a><\/p>\n\n\n\n Baumgartner, L., & Jonas, B. (2025). How the DOJ is prosecuting Nihilistic Violent Extremism as Domestic Terrorism. Just Security<\/em>, December 25. https:\/\/www.justsecurity.org\/126226\/prosecuting-nihilistic-violent-extremism-domestic-terrorism\/<\/a><\/p>\n\n\n\n Cassam, Q. (2026). Extremism without ideology. advances.in\/psychology, 1<\/em>, e945134. https:\/\/doi.org\/10.56296\/aip00062<\/a><\/p>\n\n\n\n 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<\/a><\/p>\n\n\n\n Horgan, J., & Shayler, M. (2026). Why the \u2018salad bar of ideologies\u2019 does not help us understand contemporary violent extremism. advances.in\/psychology<\/em>, 1<\/em>, e607682. https:\/\/doi.org\/10.56296\/aip00057<\/a><\/p>\n\n\n\n McCauley, C., Moskalenko, S., & Van Son, B. (2013). Characteristics of lone-wolf violent offenders: A comparison of assassins and school attackers. Perspectives on Terrorism<\/em>, 7(1), 4-24. https:\/\/pt.icct.nl\/article\/characteristics-lone-wolf-violent-offenders-comparison-assassins-and-school-attackers<\/a><\/p>\n\n\n\n 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,<\/i> 26(1), 69-85. <\/p>\n\n\n\n https:\/\/doi.org\/10.1080\/09546553.2014.849916 <\/a> 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<\/em>, 38, 211\u201337. https:\/\/journals.sfu.ca\/jd\/index.php\/jd\/article\/view\/869<\/a><\/p>\n\n\n\n McCauley, C. (2025). Can we leave ideology behind? Diagnostic, prognostic, and motivational action frames in tracking radicalisation and deradicalisation. Perspectives on Terrorism<\/em>, XIX(4). https:\/\/doi.org\/10.19165\/ntzz3710 <\/a><\/p>\n\n\n\n Perliger, A. (2026). The erosion of conceptual clarity in the study of political violence. advances.in\/psychology, 1<\/em>, e824472. https:\/\/doi.org\/10.56296\/aip00059<\/a><\/p>\n\n\n\n The White House. (2011). Empowering Local Partners to Prevent Violent Extremism in the United States. https:\/\/obammawhitehouse.archives.gov\/sites\/default\/files\/empowering<\/a>_local_partners<\/p>\n\n\n\nWhy Is Non-ideological Violence a Problem?<\/h2>\n\n\n\n
Trying to Save Ideology<\/h2>\n\n\n\n
An Alternative to Ideology<\/h2>\n\n\n\n
Conflicts of Interest<\/h2>\n\n\n\n
References<\/h2>\n\n\n\n
McCauley, C. (2017). Toward a psychology of humiliation in asymmetric conflict. American Psychologist,<\/em> 72(3), 255-265. https:\/\/doi.org\/10.1037\/amp0000063<\/a><\/p>\n\n\n\n