Introduction

Due to the historical, political and cultural conditionality in defining, the concept of radicalization as a process that leads certain individuals and groups towards the manifestation of violent extremism and acts of terrorism has been differently interpreted. Apart from objective difficulties in the definition, the reasons for the lack of consent lie in global political interests and consequences that its principled determination may have. It is best illustrated by Serbia's experience where the western powers, under the guise of "human rights protection" of the Albanian minority, first illegitimately conducted the 1999 military intervention, and then some of those powers also recognized the self-declared secession of the Autonomous Province of Kosovo and Metohija, which actually took place through the process of mass radicalization that led to terrorism.

The issue of violent extremism and terrorism arose in western countries in the 21^st century particularly after the 2001 terrorist attacks in the USA, and then in many places in the EU member states by the Islamic State of Iraq and the Levant (ISIL). In the official EU documents, terrorism is considered a major security threat to the European Union (EUROPOL, 2020). According to EUROPOL data (EUROPOL, 2020), in the three-year period from 2017 to 2019, there were as many as 453 acts of terrorism committed in the EU member states, and 3,279 people were arrested. In 2019, in the acts of terrorism in the EU member states 10 people were killed while 26 people were injured (EUROPOL, 2020, p. 11).

Radicalization and extremism form a potential framework for manipulation of those who organize politically motivated violent behaviours, as well as the state representatives who may use the fight against extremism to spread "the fear culture" among citizens and to endanger human rights under the veil of security concerns. In numerous media reports, but also in scientific literature, the concepts of radicalization, extremism and terrorism are frequently seen as synonyms, although there are clear differences among them.

Therefore, from the scientific perspective, it is important to place the notion and concept of radicalization in the space of the conceptual-theoretical debate. The first aim of this paper is to analyze the concepts of radicalization, extremism and terrorism. The first aim is to classify and explain different concepts of radicalization. Finally, the third aim is to make a framework for the development of a comprehensive and integrative theory of radicalization.

The methodological approaches used in the paper are: analysis - which on the basis of general concepts of radicalization derives specific facts about the nature of this phenomenon; synthesis - which on the basis of individual findings about the concepts of radicalization derives general elements that may serve as a framework for the development of an integrative theory of radicalization; classification - which organizes the findings about radicalization into categories enabling its clearer understanding.

The concept of extremism and terrorism

Historically, the word extremity was first used in public by Stephen Gardiner, an English bishop, in 1546 to describe his enemies (Bötticher, 2017). Etymologically, the notion of extremism refers to consistency, extremeness, and intransigence in ideas or actions. Extremism is the "behaviour that is on the border of the permitted, with the tendency of crossing the marked border" (Đorić, 2014, p. 21). Permitted behaviours are defined by positive legislation, as well as cultural, customary or moral norms.

The definitions of extremism in anti-terrorist strategies of many countries are often unclear and too broad, which enables holders of power to use such circumstances to fight against their internal political and ideological opponents, and to weaken their opposition potential (Neumann, 2017). The determination of extremism is permeated by ideologies, narrower group interests, culture-value and legal systems.

If extremism was to be determined from the aspect of human rights and negative social consequences, several conclusions could be made. Extremism is a context of both broader social violence and the result of the process of individual and group radicalization. It is a complex social phenomenon, founded on overemphasized biological needs of self-defence from "others" and the xenophobic version of understanding of a certain identity. Behind extremism, there is a system of beliefs that serves for forming and justifying violent behaviours directed towards other racial, religious, ethnic and political groups which are perceived as hostile (Simeunović, 2009).

Extremism is not a belief or behaviour originating only from religious motives, which has become a dominant discourse in interpreting Islam-motivated terrorism in the western public nowadays. The problem with this approach is the simplification and potential stigmatization of the religion that takes on different forms, from Wahhabism, postmodern Islam, radical Islam to Euro-Islam (Duhandžija-Ilić, 2017).

Extremist behaviour is present in all spheres of the society: politics, economy, sports, inside peer groups and social media, Extremist motives are often intertwined with the spheres of religion, politics, historical experience, economic and social situation and cultural beliefs.

In democratic systems, extremism is understood as an ideology of intolerance and exclusion, which is directed against the principles of democracy and human rights. An extremist is "a person whose goal is to accomplish his/her ideological belief by attacking life, freedoms and human rights" (Yu Byung-hu, 2017, p. 13). The one who has adopted violent extremist beliefs usually supports acts of terrorism and potentially is willing to participate in them. In striving to profile this concept as clearly as possible, the term of violent extremism is made.

The concept of terrorism originates from Latin words terrere and terre, meaning "to frighten" or "to intimidate".

Terrorism is defined as "a complex form of organized group and, less frequently, institutional political violence. It is characterized not only by frightening brachially physical and psychological, but also sophisticated technological methods of political struggle, usually in times of political and economic crises, and rarely in the conditions of achieved economic and political stability of a society. Through acts of terrorism, there is an attempt to achieve 'great goals' in a morbidly spectacular manner" (Simeunović, 2009, p. 80).

This form of political violence always involves violence for the purpose of achieving political goals through causing fear in the society, since it is usually accompanied by indirect victims, i.e. the suffering of innocent citizens. Psychological effects of terrorist attacks in terms of causing fear, panic and social anxieties among citizens, are considered one of the most important goals of this type of political violence. Terrorism is also a security problem, as well as a social deviation, because it endangers significant social values such as people's lives, freedom, property and the country's political system (Živaljević, Jugović, 2014).

However, it is also important to note that terrorism is not the only form of politically motivated violence, and all political violence is not the same as terrorism either (Beriša, 2013). There are multiple forms of political violence in addition to terrorism such as: threat of force, coercion, pressure, psycho-physical abuse, repression, political murder, assassination, terror etc. (Simeunović, 1993). Moreover, political violence can sometimes have a positive role, particularly when it comes to the fight against terrorism or to defensive war (Đorić, 2013).

From the political perspective, approaches to terrorism are often inconsistent and interest-based: identical violent political activities of individuals or groups in one case are labelled as terrorism, while in another they are promoted as progressive ideas directed towards achieving human and national rights and freedoms.

When types of terrorism are analyzed, it is associated with ideological sources, motives or extremist beliefs. Although motives for terrorism may be various, usually one ideology is dominant. Therefore, according to EUROPOL (EUROPOL, 2020, pp. 94-95), in the EU member states there are five forms of ideologically motivated terrorism. Those are: 1) jihadist; 2) right-oriented; 3) left-oriented and anarchist; 4) ethno-nationalist and separatist; and 5) focuses on a single social problem.

Radicalism and radicalization

The concept of radicalism (Latin radicis, radicalis - root, from the root) usually refers to political ideas about the necessity of an overall change of a social or political system. This approach to social change may be also understood as a driving force of the society (Yu Byung-hu, 2017). Throughout history, radical movements had many progressive and liberal political ideologies. The concept of radicalism is also found in the names of political parties within groups of the so-called extreme right or left political orientations. Moreover, radicalism is associated with certain social and religious groups as well, so the term "religious radicalism" is also used. Historically, radical movements have been more oriented towards progressive reformism than utopian extremism and glorification of mass violence (Bötticher, 2017).

On the other hand, radicalization refers to the process that leads to certain political beliefs being accompanied by the willingness of individuals to give direct support or be engaged in acts of violence (Dalgaard-Nielsen, 2010). Being prepared for an act of violence, which is perceived as the only means in political action, is the ultimate outcome of the process of radicalization. For that reason, radicalization is most often associated with political violence as its key feature (Neumann, 2013).

Political violence is part of social violence occurring through the direct or indirect (latent) use of force in the sphere of politics or political processes. It refers to the use of force over conscience, body, life, will or material goods of an actual or potential political opponent (Simeunović, 1993).

Radicalization can be defined as a process of building extremist beliefs, feelings and behaviours that are opposite to basic social values, democratic principles and universal human rights. These beliefs advocate the supremacy of a group that is based on racial, religious, economic or social affiliation (Trip, S., et al., 2019). Radicalization is a "process in which a person becomes an extremist" (Borum, 2011, pp. 9).

In literature, the narrower term of terrorist radicalization is also mentioned in literature. That is the process during which an individual or a group of people are openly exposed to ideological terrorist messages and systems of beliefs, undergoing the transformation of their beliefs from relatively moderate ones to the adoption of terrorist views, ideals and aspirations which may lead to committing an act of terrorism (Kisić, Barišić, Đukanović, 2019). This process is conditioned by historical, social, cultural, political, psychological and religious factors.

Concepts of understanding radicalization

By analyzing the scientific and expert literature that deals with radicalization, we see that the phenomenon can be classified through three general approaches with their respective concepts (Table 1).

Table 1. General approaches and concepts of radicalization
Табела 1. Општи приступи и концепти радикализације

Општи приступ/General approach	Концепти/Concepts
Структурални контексти радикализације/ Structural contexts of radicalization	– Социјална дезинтеграција/Social disintegration – Политички покретачи радикализације/Political drivers of radicalization – Медијска изложеност и употреба/Media exposure and use – Концепт погодујућих услова и ресурса/Concept of favourable conditions and resources
Фактори ризика радикализације/ Risk factors of radicalization	– Когнитивни и бихејвиорални фактори ризика/Cognitive and behavioural factors – Фактори одбијања, привлачења и контекста/Push, pull and contextual factors – Политичка социјализација у условима дуготрајних сукоба/Political socialization in long-lasting conflicts – „Усамљени вук“/“Lone wolf”
Развој или ток радикализације/ Development or course of radicalization	– Постепени ток развоја радикализације/Gradual course of radicalization development – „Степенице ка тероризму“/“Staircase to terrorism” – Линеарни процес/Linear process – Групна динамика/Group dynamimcs

Structural context approaches to radicalization

The concept of social disintegration. Structural characteristics of those societies that produce large inequalities in the sphere of economic, political, ethnic and cultural rights create in increased risk of the occurrence of radicalization. The risk groups regarding the development of violent extremism include those groups that are more experienced in social exclusion in terms of poor life chances, discriminations, frustration, betrayed expectations, social deprivation, marginalization, social non-integration, poor economic opportunities, inaccessibility of social rights and education, forced migrations, involvement in illegal economic activities etc. Those individuals who experience repression and humiliation in their everyday life may be more susceptible to highly politicized and emotional images of their compatriots' suffering (USAID, 2017). Some studies confirm the connection between social exclusion, non-acceptance of the cultural identity and radicalization (Doosje et al., 2012).

The concept of political drivers of radicalization. When explaining radicalization, some approaches particularly emphasize political drivers of this process, so in that respect the following are listed (USAID, 2017, pp. 6–7): denial of political rights and civil freedoms; severe government repression and grave violations of human rights; foreign occupation; political and military interference of other countries; endemic corruption and impunity of closely-connected elites; isolated regions with low population density; local conflicts and the inability of governments to overcome them; discredited governments and weak political opposition; intimidation and coercion by extremist groups, where government bodies cannot provide protection to their citizens; the perception of the international system as essentially unjust, hostile and discriminatory towards some societies and nations; "proactive" extremist (e.g. religious) programs present in the community.

The concept of media exposure and use. Through this discourse, radicalization is perceived as a media-mediated phenomenon and process. Digital and traditional media are seen as the space and instrument of different stages of radicalization - from propaganda, when the followers of ideas are found and messages of extremist organizations are promoted, to the training for committing acts of terrorism: bomb making, weapons use or attack coordination. The concept of terrorist propaganda through demagogy, populism and extremist narratives involves demonizing the enemy, assuming the role of a victim, sending messages about one's own superiority, creating beliefs about religious and ideological purity, creation of an emotional relationship with the surrealist "god's orders" etc. A special area of radicalization is building motivation and training for committing cyberterrorism through attacks on computer networks and information with the aim of intimidating or forcing the government and other political subjects to realize some interests of the terrorists.

The concept of favourable conditions and resources. This concept starts from the need to understand suitable conditions and resources for the development of radicalization. The conditions refer to the dominant cultural atmosphere in a narrower social environment, relations of power and authority within a community, the degree of organization of the network that motivates and recruits group members, method of conspiratorial action, financing activities and instruments of resource mobilization necessary for conducting terrorist attacks (people, transportation, flats, weapons etc.).

Radicalization risk factor approaches

The concept of cognitive and behavioural risk factors. According to Dzhekova (Dzhekova et al., 2017), radicalization is a process taking place through the effects of two groups of risk factors. They are behavioural (such as changes in someone's behaviour or appearance) and cognitive (expressing opinions, beliefs and attitudes verbally). Each of these two factors, depending on the risk degree, can be divided into 3 categories: suggestive, warning and high-risk ones (Dzhekova et al., 2017).

Cognitive suggestive factors are: open expression of dissatisfaction towards social or personal life conditions; expression of a dichotomous view of the world (us-them); disrespect or renouncement of the legitimacy of authorities; negative narratives towards certain groups (such as LGBT community, other ethnic, religious and political groups). Warning cognitive signs are: spreading ideas about illegitimate radical changes of the democratic society; open expression of support to terrorist organizations and goals; open expression of violence-supporting attitudes.

Suggestive behavioural indicators consist of: termination of ties with families and friends and social withdrawal; visible changes in practising religious rituals and other everyday habits; exposure to the influence of religious and ideological leaders and recruiters of extremist groups; acceptance of extreme political rhetoric; social isolation of some social groups or entire communities as a consequence of marginalization. Warning behavioural indicators are: possession or distribution of extremist literature and propaganda contents, organizing, leading or attending protests with the aim of providing support to extremist ideas and goals; contact with extremist groups or membership in them; involvement in criminal activities.

High-risk indicators are: travelling to the countries with high political risks and conflicts, taking part in combat and military training; purchase of weapons and necessary material for conducting a violent act of terrorism.

The above-mentioned factors are an indicative set of potential signs pointing to the higher probability of radicalization, but not necessarily to its development in the end. The reason for it is that risk factors also interact with protection factors such as: social competencies, level of self-esteem, intelligence, adults' support to the young, pro-social and non-extremist environment etc.

The concept of push, pull factors and conceptual factors. This concept distinguishes the impact of three groups of factors on the development of radicalization (Kisić, Barišić, Đukanović, 2019, pp. 11–13).

Push factors refer to negative social, cultural and political characteristics of a certain social environment, such as: social exclusion, inequality, poverty, discrimination, limited access to good-quality education, unemployment, the feeling of social injustice, deprivation of civil rights and freedoms, non-acceptance of group identities, cultural oppression, political dissatisfaction etc.

Pull factors are of a personal nature and indicate positive characteristics and benefits offered to some people by their membership in an extremist organization. These factors include; the feeling of belonging and importance, close people who are already members of an extremist group, attractiveness of the leader, spiritual fulfilment, employment, financial aid, adventure, social status, peer respect, self-confidence and personal empowerment, feeling of perspective, perception of an extremist group as morally proper, cult building of (radial, religious or gender) superiority of the group in relation to other communities in the society.

Contextual factors refer to the attitude of government institutions that encourages radicalization. Those are: repressive actions of government bodies; endangerment of human rights; non-functional management and public citizen services; crime and criminal parts of town rarely visited by the police; weak security apparatus of a country, deeply rooted corruption; undemocratic society, autocratic concept of rule with poor or fictitious opposition etc.

The concept of political socialization in the conditions of long-lasting ethno-national and religious conflicts. The radicalization process may also have its sources in historical-political relations existing in some parts of the world and countries. Individual and group radicalization occurs much more frequently in those regions with historically persisting political and ethno-religious conflicts. The examples of long-lasting unresolved conflicts of Israelis and Palestinians, of Irish Protestants and Catholics, and of Turks and Kurds, are some of the indicators as to how violent extremism develops in the permanent conflict conditions. There is a vicious circle of violence that is difficult to break. Violence through wars and terrorism always takes victims, and therefore each side in a conflict gets "legitimacy for revenge" and defence of national or religious honour. The conflicting sides in these conflicts create historical memories and their own truths about the cause and victims of the conflict. In such circumstances, political socialization develops towards adopting the model of intolerance, the feeling of national and ethnic endangerment and "rectification of historical injustices". This only increases the potential for the development of radicalization.

The "lone wolf " concept. "Lone wolf terrorism" is a phenomenon existing ever since the 19^th century as a part of different anarchist beliefs advocating the idea of "individual resistance with no leadership". This concept explains violent extremism and acts of terrorism of those people who do not belong to terrorist organizations or groups. Those are individuals who commit politically motivated violence, but without any direct relationship the like-minded people or with the organizers of violent extremist actions. They are self-radicalized people who are difficult to detect from the position of security services and to assess the degree of their motivation and willingness for acts of terrorism (Spaaij, 2012).

"Lone wolf " radicalization is explained as "a multi-factor process involving several risk factors: 1) looking for the meaning in self-sacrifice for higher goals; 2) moral belief that "justice" and "revenge" are accomplished by a violent act against an imaginary or real enemy; 3) some psychopathological features of an individual, such as antisocial personality disorder, obsessive-compulsive disorder, schizophrenia, excessively lone wolf nature of a person; 4) influence of a dysfunctional family, in particular the one with prevalent aggressive-paranoid behaviours; 5) motivation and emotionalization by an ideology; 6) the use of the Internet and cybergroups for developing an ideology and independently conceiving acts of terrorism. The 2011 case of radicalization of extreme right-wing Anders Behring Breivik, who killed 69 and injured 60 teenagers in a youth summer camp of the Social Democratic Youth in Oslo, is one of the best known examples of "lone wolf" terrorism in Europe (Bartlett, 2014).

Radicalization development course approaches

The concept of the gradual course of radicalization development. This approach indicates that radicalization occurs gradually, through the action of social movements and ideologies that give the meanings of political reality to individuals. Therefore, radicalization is understood as a process of obtaining the identity that leads towards political extremism and the desire to get involved in terrorist activities. This process may take place through a group, an organization or via media. Individuals exposed to political socialization that promotes violent extremism as an instrument of political struggle, undergo stages during which they gradually develop their motives for violent political acting. Those are usually four general stages: 1) exposure to a new view of the world and the existence of the cognitive openness, 2) ideological creating of the meaning of the context of the problem and the aspirations of the group an individual belongs to; 3) enticing group narratives about the history of problems and conflicts, group endangerment, ethics of struggle, legitimacy of violent acting; and 4) joining a group.

The "staircase to terrorism" concept. According to this concept, radicalization is a psychological process of the individual's transition leading to violent extremism (Moghaddam, 2005). Radicalization, symbolically speaking, takes place as a process of "climbing the staircase". Every individual decides which stair to stop on, if he/she beliefs that his/her opportunities for terrorist action are reduced. This begins with the individual's feeling of dissatisfaction with the social position, and the perception that his/her identity is endangered so that he/she is deprived of the values of the society he/she lives in. According to Moghaddam's model, people always strive to improve their social position. If this attempt is unsuccessful, it leads to despair or fury. These emotions are projected on the "enemy" that is considered the cause of a personal failure. The "enemy" can be another ethnic group, individuals from the system of power, or a political order. When fury against the "enemy" is created, some individuals accept violent extremist ideologies and show disposition towards terrorist activities. Then they join extremist groups and isolate themselves from the community. Some of them also decide to take direct part in acts of terrorism. This concept indicates that an individual can always return to the "stair below" too, and thus embark on the deradicalization process.

The linear process concept. This concept served to explain the development of jihadist terrorism among the citizens of Islamic religion who live in western countries. According to the concept, radicalization has four stages (Silber, Bhatt, 2007, pp. 1) "pre-radicalization" - the time preceding the individual's exposure to Islamic fundamentalism; 2) "self-identification" - through studying Salafi Islam, individuals accept ideological doctrines and join other followers of Islamic fundamentalism; 3) "indoctrination" - the strengthening of radicalization through commitment to the fundamentalist ideology and its followers; 4) "jihadization" - accepting jihad and fulfilment of personal obligations in violent activities.

The group dynamics concept. According to this approach, radicalization is a social-psychological process. An individual develops extremist political beliefs under the influence of the group he/she belongs to. Social psychology shows that individual behaviours change under the group influence. The group is able to create a higher level of the individual's courage and a lower level of rationality in decisions, a lower level of behaviour self-control, as well as to strengthen prejudice against other social groups. Moreover, the self-responsibility degree is also reduced within the group. The group effect has a particularly strong effect on those individuals that are isolated from the broader society, where the group offers social acceptance and awards for the desired behaviour. This also increases the degree of the individual's obedience and easier acceptance of group requirements, even when they are of a violent extremist nature. The research of radicalization from this concept particularly opens the question of the group's action in the conditions of life in prison. Prisons often facilitate the spread of the extremist ideology, giving prisoners the opportunity to make alliances, exchange experiences and recruit potential perpetrators of an act of terrorism (Rushchenko, 2019).

Conclusion

As this paper shows, radicalization is explained by different concepts. In the scientific community, there is no comprehensively developed and integrative theory to explain this complex dynamic phenomenon. Some concepts have been made for the purpose of the action of security services, e.g. detecting risk factors because of early identification of radicalized individuals and groups. Other concepts are based on general psychological and social theories, such as the theory of the group. The third group of concepts explains political, social, economic, media, cultural and historical contexts that contribute to the development of radicalism. The fourth group deals with individual and group conditions of political socialization contributing to radicalization etc.

The closest to the comprehensive theory is Moghaddam's concept of the "staircase to terrorism", which perceives radicalization in an interactive psycho-social process that gradually takes place among individual-group-community-society. However, its weakness is the fact that it neglects more broadly connected political, historical and resource causes of radicalization.

The comprehensive theory of radicalism should take into account different mutually conditioned and connected dimensions of this process. In our opinion, it could be called the integrative theory of radicalization development. The basic starting point is that radicalization is a process taking place at three levels: micro (individual psycho-social features), meso (features of a narrower community) and macro (the broader society and the global political situation). The conditions of this process have subjective and objective characteristics.

The causes of radicalization can be seen as structural, economic, cultural, social, resource, historical and individual. Radicalization also has direct risk factors or drivers, like a set of mutually conditioned factors relevant to its development. Radicalization is manifested at three basic levels - individual, group and mass. It is a process with the interactive course, "mechanisms" or stages of development. In addition, radicalization takes place through instruments such as media and propaganda as well.

The connection between these dimensions is reflected in the interactive relationship existing between, for example, conditions, causes and factors of radicalization, and its stages and course. Moreover, while structural causal factors are contextual factors, the specific features of individuals and narrower communities are direct drivers of radicalization. Concurrent action of several causes and risk factors contributes to higher probability of the negative radicalization outcome, i.e. the development of violent extremism and terrorism. The comprehensive theory, apart from the scientific significance, is also socially significant because it more broadly and systematically points to the directions of the prevention of radicalization, as well as the steps in the deradicalization processes of those individuals and groups which are at one of the stairs of development leading towards violent extremism.