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Extremism (represented on both sides of the political spectrum) is any ideology or political act far outside the perceived political center of a society; or otherwise claimed to violate common moral standards. In democratic societies, individuals or groups that advocate the replacement of democracy with an authoritarian regime are labelled extremists; in authoritarian societies, people who espouse democratic or otherwise liberal ideals are labelled as extremists by the ruling class or government.
Extremism is usually contrasted with moderation, and extremists with moderates (for example, in contemporary discussions in Western countries of Islam, or of Islamic political movements, it is common for there to be a heavy stress on the distinction between extremist and moderate Muslims, and it is also not uncommon to necessarily define distinctions regarding extremist Christians as opposed to moderate Christians, as in countries such as the United States).
The term extremism is almost invariably used pejoratively, however the term may also sometimes be associated with person(s) who have different view(s) which is not consistent with the existing norm(s). It need not necessarily imply that the person is a threat to the society or the government or any other agency.
Problem of definition of extremism 
In different realms at different times were many different definitions of "extremism". Dr. Peter T. Coleman and Dr. Andrea Bartoli give short observation of definitions:
|“||Extremism is a complex phenomenon, although its complexity is often hard to see. Most simply, it can be defined as activities (beliefs, attitudes, feelings, actions, strategies) of a character far removed from the ordinary. In conflict settings it manifests as a severe form of conflict engagement. However, the labeling of activities, people, and groups as “extremist”, and the defining of what is “ordinary” in any setting is always a subjective and political matter. Thus, we suggest that any discussion of extremism be mindful of the following:
Radicalism or extremism? 
The terms extremism or extremist are almost always exonymic — i.e. applied by others to a group rather than by a group labeling itself. Rather than labeling themselves extremist, those labeled as such might describe themselves as, for example, political radicals. There is no political party that calls itself "right-wing extremist" or "left-wing extremist", and there is no sect of any religion that calls itself "extremist" or which calls its doctrine "extremism".
The term extremist is used to describe groups and individuals who have become radicalized, in some way, even though the term radical originally meant to go to the root of a (social) problem. The term radical is one not normally regarded as pejorative (except perhaps in the United States of America) and, unlike extremist, is sometimes used by groups in their description of themselves.
The term extremist is often used with reference to those who use or advocate violence against the will of society at large, but it is also used by some to describe those who advocate or use violence to enforce the will of the social body, such as a government or majority constituency. Those described as extremist would in general not accept that what they practice or advocate constitutes violence and would instead speak in terms of acts of "resistance"or militant action or the use of force. The word violence cannot be regarded as value-neutral. Ideology and methodology often become inextricably linked under the single term extremism.
The notion that there is a philosophy which can be described as extremism is considered by some to be suspect. Within sociology, several academics who track (and are critical of) extreme right-wing groups have objected to the term extremist, which was popularized by centrist sociologists in the 1960s and 1970s. As Jerome Himmelstein states the case: "At best this characterization tells us nothing substantive about the people it labels; at worst it paints a false picture." (Himmelstein, p. 7). The act of labeling a person, group or action as extremist is sometimes claimed to be a technique to further a political goal — especially by governments seeking to defend the status quo, or political centrists. In any event, the term extremist — like the word violence— cannot be regarded as value-neutral.
Theories of extremism 
Laird Wilcox identifies 21 alleged traits of a "political extremist", ranging from behaviour like "a tendency to character assassination", over hateful behaviour like "name calling and labelling", to general character traits like "a tendency to view opponents and critics as essentially evil", "a tendency to substitute intimidation for argument" or "groupthink".
Eric Hoffer and Arthur Schlesinger, Jr. were two political writers during the mid-20th century who gave what purported to be accounts of "political extremism". Hoffer wrote books such as The True Believer and The Passionate State of Mind about the psychology and sociology of those who join "fanatical" mass movements. Schlesinger wrote books such as The Vital Center, championing a supposed "center" of politics within which "mainstream" political discourse takes place, and underscoring the alleged need for societies to draw definite lines regarding what falls outside of this acceptability.
Joining extremist groups has been seen to arise from beliefs about the acceptability of aggression towards the group’s target. For example, in Pakistan, beliefs about the acceptability of aggression against Jews were shown to predict who would join an extremist anti-Semitic group. Cultural differences in acceptability about aggression towards certain groups may explain extremism towards certain targets, and as these beliefs can be easily changed through intervention, this may offer a way in which extremism can be discouraged.
"Extremism" is not a stand-alone characteristic. The attitude or behavior of an "extremist" may be represented as part of a spectrum which ranges from mild interest through "obsession" to "fanaticism" and "extremism". The alleged similarity between the "extreme left" and "extreme right", or perhaps between different religious "zealots", may mean only that all these are "unacceptable" from the standpoint of a supposed mainstream or majority.
Economist Ronald Wintrobe argues that many extremist movements, even though having completely different ideologies share a common set of characteristics. As an example, he lists the following common characteristics between "Jewish fundamentalists" and "the extremists of Hamas":
- Both are against any compromise with the other side.
- Both want the entire land of Palestine for their group.
- Both are entirely sure of their position.
- Both advocate and sometimes use violence to achieve their ends.
- Both are nationalistic.
- Both are intolerant of dissent within their group.
- Both demonize the other side, so that the members of Hamas, as viewed by the Israeli fundamentalists, sometimes sound exactly like the Israeli fundamentalists as viewed by Hamas.
Among the loved explanations for extremism is one that views it as a plague. Arno Gruen said, "The lack of identity associated with extremists is the result of self-destructive self-hatred that leads to feelings of revenge toward life itself, and a compulsion to kill one’s own humanness." Thus extremism is seen as not a tactic, nor an ideology, but as a pathological illness which feeds on the destruction of life.
Another view is that extremism is an emotional outlet for severe feelings stemming from "persistent experiences of oppression, insecurity, humiliation, resentment, loss, and rage" which are presumed to "lead individuals and groups to adopt conflict engagement strategies which “fit” or feel consistent with these experiences".
Uses of the term in "mainstream" politics 
Barry Goldwater said, "Extremism in the defense of liberty is no vice; moderation in the pursuit of justice is no virtue" at the 1964 Republican Convention in a sentence attributed to his speechwriter Karl Hess.
Robert F. Kennedy said, "What is objectionable, what is dangerous about extremists is not that they are extreme but that they are intolerant. The evil is not what they say about their cause, but what they say about their opponents."
Since the 1990s, in United States politics the term Sister Souljah moment has been used to describe a politician's public repudiation of an allegedly extremist person or group, statement, or position which might otherwise be associated with his own party.
Other terms 
See also 
- Domestic Extremism Lexicon
- False consensus effect
- Political extremism in Japan
- Political extremism in Switzerland
- George, John and Laird Wilcox. Nazis, Communists, Klansmen, and Others on the Fringe: Political Extremism in America Prometheus Books, 1992. (ISBN 0-87975-680-2)
- Himmelstein, Jerome L. All But Sleeping with the Enemy: Studying the Radical Right Up Close ASA, San Francisco: 1988
- Hoffer, Eric. The True Believer: Thoughts on the Nature of Mass Movements. Various editions, first published 1951.
- Schlesinger, Arthur. The Vital Center: The Politics of Freedom. Various editions, first published 1949.
- Wilcox, Laird. "What Is Political Extremism", retrieved from The Voluntaryist newsletter #27, 1987
- Ronald Wintrobe (2006). Rational extremism: the political economy of radicalism. Cambridge University Press. ISBN 978-0-521-85964-6.
- Dr. Peter T. Coleman and Dr. Andrea Bartoli: Addressing Extremism, pp. 3-4
- G. M. Tamás: On Post-Fascism, Boston Review, summer 2000
- Amjad, N., & Wood, A. M. (2009). Identifying and changing the normative beliefs about aggression which lead young Muslim adults to join extremist anti-Semitic groups in Pakistan. Aggressive Behavior, 35, 514-519
- Wintrobe (2006), p. 5