The definition of terrorism lies in the gray area that exists between crime and war, although experts disagree as to its approximate location. Some professionals who have spent their careers closely following the various competing theories have resigned themselves to the conclusion that terrorism resists classification. According to professor of international politics Colin S. Gray, terrorism results from various causes that defy any clear distinction “between the political and the criminal.”

Some people primarily equate terrorism with war. Noted scholar Noam Chomsky, for one, cites a section of U.S. code that describes terrorism as “the calculated use of violence or threat of violence to attain goals that are political, religious, or ideological.” Chomsky argues that this definition of terrorism is essentially the definition of war: It is something that “is conducted by them against us,” with “them” meaning an...