Terrorism is a sensational but widely used label for the sort of "warfare from below" which challenges state authority and spreads fear among a wider circle than those who are directly harmed. We know that it is not senseless violence perpetrated by lunatics; it is often violence in the calculated service of an ideal. Neither wars nor acts of private violence for public reasons are more tolerable because we understand the reasons for which they are enacted, but addressing those reasons rather than isolating and demonizing their adherents is likely to be more effective than a violent or repressive response to political violence. As the "terrorism scares" of the 1980s abated, scholarly interest in small group political violence likewise lessened. After the bombing of the Oklahoma City Federal Building, the assassination of Prime Minister Rabin, and continued acts of violence by militants at home and abroad, we encourage further investigations of the ideas and emotions which sustain people willing to use violence for their cause.