Terrorism is typically defined as premeditated, politically motivated attacks or threats of attacks by substate actors (that is, groups that are smaller than states) against noncombatants. Terrorists are those people who carry out or aid and abet in such attacks. Still, no widely agreed-upon definition exists. Definitional debates center on two issues: first, whether states as well as substate actors should be called “terrorists,” and second, whether the term is so misused and inexact that it should be discarded altogether.

It is remarkable that an agreed-upon definition does not exist for a term as widely used in the media, academe, and common parlance as terrorism. Indeed, some scholars even argue that the term is so imprecise that it should be dropped altogether. The U.S. Department of ...