Very little has been written on the subject of terrorism from a philosophical viewpoint. What little exists generally presupposes terrorism to be either senseless brutality or romanticized heroism. We argue that it is neither. Many writers conflate terrorism with either revolutionary or criminal activity. We contend that it is a separate and recent phenomenon, defining terrorism as violence directed, as a matter of political strategy, against innocent persons. We consider three possible arguments that may be offered in defense of terrorism. First, the Economy of Scale argument, which supposes terrorism to be the "cheapest form of warfare." Second, the Consciousness-Raising argument, contending that terrorism is warranted provided that it makes the public aware of institutional injustice. Third, the Collective Guilt argument, which holds that the public is sealed by their silence. We argue that none of these arguments holds up under close scrutiny, and we further consider general objections that can be raised against any terrorist activity. We conclude with a look into the terrorist's mind, noting that he or she interprets the world in starkly polar terms between good and evil. We describe the ideological rift that exists between the liberal democratic tradition - of which our arguments are representative - and the ideologies of terrorism.