This chapter focuses on political extremism, on both the left and right, and how it and other forms of nonreligious ideological extremism can spawn terrorist activities. It identifies and describes specific ideologies, factions, and issues that have been associated with terrorism and then looks more closely at specific extremist groups that are like most others in some ways and unusual in others, to exemplify the problem of extremism and its variants and how the common product of extremism – isolation – can have deadly consequences, both for members of extremist groups and for others.

Extremist Ideologies

Terrorism grows typically out of a constellation of factors, but it is almost always a product of extremist belief. In the post-9/11 era, discussions about extremism are usually about religious extremism. However, in the more than two centuries since the word “terrorism” was first used, terrorism has been linked predominantly to political, racial, and ethnic extremism, rather than religious extremism (George and Wilcox, 1996; Hewitt, 2003; Pape, 2005). In the case of both political and religious extremism – and recognizing that it is not always a straightforward matter to disentangle the two – one of the great puzzles has been that of figuring out how to reduce or eliminate the tensions that emerge from extremist factions and give rise to acts of aggression.