INTRODUCTION

Political extremism is a multidimensional phenomenon. It can be taken to refer to, for example, the tail ends of the distribution of worldviews and beliefs held by individuals in a society, the kind of objectives sought, the means used in the pursuit of those objectives, or the preeminent position accorded to one specific issue over all others. In this chapter, we focus on a particular dimension of extremism – namely the intolerance, unwillingness to compromise, and rejection of evidence contradicting one's beliefs that are often associated with the phenomenon.

We look at the forces, within a social environment, that can contribute to the development of the above attitudes (Section 2). We then look at mechanisms that help reinforce and diffuse extreme positions (Sections 3 and 4). Much of what we say in these sections applies to all forms of extremism – whether religious, social, scientific, cultural or political. We focus on the last.

Political extremism becomes a socially relevant phenomenon when it involves the mobilization of individuals and the formation of groups that pursue objectives and make use of means that impose external costs deemed to be unacceptable.