As I have learned in Organized Crimes class, the definition of terrorism is the use or threat of repeated violence in support or opposition to some authority where violence is employed to induce fear of a similar attack in as many non-immediate victims as possible so that those so threatened accept and comply with the demands of the terrorists. Terrorism is simply a means to an end. The terrorists can have a valid objective. They use terrorist means to gain their objective.
These are characteristics of a terrorist
a. dissatisfaction with life
b. "true believer"
c. attribute "evil" motives to those outside their group
