“Extremism” and “radicalization” are so-called “fuzzy” terms: although it is fairly easy to tell a view that is truly extreme from one that is obviously mainstream, there is a large gray area in which it is not obvious whether a view is or is not extreme. Tools other than common sense are therefore called for.
One approach is to look at the core meaning of the terms involved. In principle, a distinction might be made between the terms “extreme” and “radical” on the basis that “extreme” indicates the degree of the position taken on some issue while “radical” indicates a particular approach: going to the root (Latin radix) of an issue. A radical change to a system is thus more extensive than a mere reform.1 In contrast, it is possible to be extreme in one’s resistance to change as well as extreme in one’s insistence on change. In practice, however, the distinction is rarely made and the terms are used interchangeably. “Radicalization” thus denotes movement towards an extreme position as well as a radical one. Occupying such a position can be described as “extremism” or “radicalism,” though the latter term is rarely used.
The problem, of course, is that while the mean may often be golden and extremes therefore inherently undesirable, radical change is sometimes needed. That a view is extreme does not always mean it is wrong. We always have to ask: extreme in relation to what? And in what circumstances? In most European countries, questioning the acceptability of homosexuality is an extreme position; in most Muslim countries, it is advocating the acceptability of homosexuality that is extreme. Whether or not a view is extreme, then, does not on its own get us very far.
If “extremism” cannot be defined in abstract principle, it might be helpful to see how it is defined by states. This varies. In contemporary Denmark, the government considers it extremism to show “lack of respect for other people's freedom and rights” or to hold “simplified world views… where particular groups or social conditions are seen as threatening.”2 This certainly covers the so-called Islamic State, but it also covers a lot more. Many people have simplified world views, including some who occupy high office, and most electoral campaigns identify particular groups or social conditions as threatening.
Official definitions of “extremism” are not always so wide. Some countries refer not to “extremism” but to “violent extremism.” According to the FBI, violent extremism is “encouraging, condoning, justifying, or supporting the commission of a violent act to achieve political, ideological, religious, social, or economic goals.”3 The emphasis here is not on the type of view—whether it is respectful or simplified—but on its impact on violence, which solves many problems. Definitions of “violent extremism” are not always so narrow, however. The European Union, which is also concerned with “violent extremism,” understands radicalization in terms of “ideology that could lead to the commitment of terrorist acts”4 (my emphasis), which raises the problem of how to understand extremism that does not lead to terrorism. In the United Kingdom, violent extremism is “vocal or active opposition to fundamental British values, including democracy, the rule of law, individual liberty and mutual respect and tolerance of different faiths and beliefs.”5 There is no requirement, then, for any connection with violence whatsoever, and lack of respect is extremism in the UK, just as it is in Denmark.
One reason that official definitions of extremism are so wide may be that extremism is not really the issue. It is actually not obvious that ideology plays a decisive role in violent radicalization. Much research into recruitment into both terrorist and religious groups shows the importance of social networks, and of experiences that jolt people into action.6 The arrest or killing of a close relative is an obvious example of an event that can cause violent radicalization without ideology playing any significant role. Many studies of religious conversion show that networks are more important than theology: people join the group first and accept its teachings later.7 The same may well be true of violent radicalization.
This has led to a schizophrenic approach by Western governments, which on the one hand emphasize the importance of extremism in principle and on the other hand look for non-ideological factors in practice. One of the more advanced models, produced by the Danish government, assesses not only a person’s views, rhetoric, and attitudes to violence, which might or might not be extreme, but also their criminal record, social relations, self-esteem, social competences, cognitive skills, alcohol use, relations with parents, participation in “organized free-time activities,” and school performance, among other things.8 This model focuses on factors other than extremism.
For these and other reasons, attempts to measure the extent of violent extremism have generally failed. Although it has often been said that one person’s terrorist is another person’s freedom fighter, the real problem is that one person’s terrorist is often another person’s combatant. Major armed conflicts often involve groups that can be seen as terrorists and tactics that can be seen as terrorism, and so may be understood in terms of violent extremism. Recent and continuing conflicts in Iraq, Syria, and Afghanistan provide obvious examples of this. An attempt to count the causalities of violent extremism thus easily ends up listing civil wars, since attacks and causalities in a civil war always vastly outnumber those in a country that is mostly at peace.
The real problem may not be violent extremism, but civil war or even interstate conflict. Long-running civil wars tend to involve other states, and while interstate wars have recently been declining in frequency, it is not clear that state engagement in civil wars in other states has declined in the same way.
Civil wars are as old as humanity, and probably older than interstate wars, as there were doubtless organized group conflicts before there were states. Humans evolved to join groups and to struggle against other groups. Today, the nation-state is seen as the primary group with which everyone should identify, and for which everyone should be prepared to make sacrifices. The nation-state, however, probably dates only from the French revolution, and other groups still matter—sometimes political groups, but usually ethnic, religious, or both. The existence of stateless nations from the Kurds to the Chechens and the Uighurs provides non-state groups that have wide appeal and is one of the major causes of conflict. Stateless nations are now often made up of Muslims, but that reflects recent political history. During the nineteenth century, the stateless nations were the Greeks, the Bulgarians, and the Armenians, all Christian. In most of these cases, now as in the nineteenth century, religion and ethnicity merge. On a global scale, mismatches between ethnic identity and nation-states have certainly caused much more death and suffering than any variety of extremism. Perhaps that is where the real problem lies.
 Paz, O. (1978). The Labyrinth of Solitude. New York: Grove Press, 21–22.
 FBI. (ND). What is Violent Extremism? https://www.fbi.gov/cve508/teen-website/what-is-violent-extremism, accessed April 8, 2019.
 European Commission. (ND). Radicalisation. Migration and Home Affairs. https://ec.europa.eu/home-affairs/what-we-do/policies/crisis-and-terrorism/radicalisation_en, accessed April 8, 2019.
 HM Government. (2013). Tackling extremism in the UK: Report from the Prime Minister’s Task Force on Tackling Radicalisation and Extremism. London: Cabinet Office.
 Sageman, M. (2004). Understanding Terror Networks. Philadelphia: University of Pennsylvania Press, 137-173.
 Stark, R. & Sims Bainbridge, W. (1980). Networks of Faith: Interpersonal Bonds and Recruitment to Cults and Sects. American Journal of Sociology 85(6), 1376–95; Barker, E. (1984). The Making of a Moonie: Brainwashing or Choice? Oxford: Blackwell.
 Nationalt Center for Forebyggelse af Ekstremisme, Vurderingsværktøj til anvendelse ved bekymring for ekstremisme: Analyse af risiko & trussel, and Vurderingsværktøj til anvendelse ved bekymring for ekstremisme: Analyse af trivsel & modstandskraft, https://stopekstremisme.dk/filer/redskab-3-til-vurderingsvaerktoj-risiko-og-trussel.pdf and https://stopekstremisme.dk/filer/redskab-3-til-vurderingsvaerktoj-trivsel-og-modstandskraft.pdf, accessed April 8, 2019.