What extremism is, how extremist ideologies are constructed, and why extremism can escalate into violence.

A  rising tide of extremist movements threaten to destabilize civil  societies around the globe. It has never been more important to  understand extremism, yet the dictionary definition—a logical starting  point in a search for understanding—tells us only that extremism is “the  quality or state of being extreme.” In this volume in the MIT Press  Essential Knowledge series, J. M. Berger offers a nuanced introduction  to extremist movements, explaining what extremism is, how extremist  ideologies are constructed, and why extremism can escalate into  violence. Berger shows that although the ideological content of  extremist movements varies widely, there are common structural elements.

Berger, an expert on extremist movements and terrorism, explains  that extremism arises from a perception of “us versus them,”  intensified by the conviction that the success of “us” is inseparable  from hostile acts against “them.” Extremism differs from ordinary  unpleasantness—run-of-the-mill hatred and racism—by its sweeping  rationalization of an insistence on violence. Berger illustrates his  argument with case studies and examples from around the world and  throughout history, from the destruction of Carthage by the Romans—often  called “the first genocide”—to the apocalyptic jihadism of Al Qaeda,  America's new “alt-right,” and the anti-Semitic conspiracy tract The  Protocols of the Elders of Zion. He describes the evolution of identity  movements, individual and group radicalization, and more. If we  understand the causes of extremism, and the common elements of extremist  movements, Berger says, we will be more effective in countering it.