Joseph Stack, the Texas man who burned his house down and then recently flew a plane into an IRS building, killing one person, has some stark similarities to the the suicide bomber I write about in The Hidden Brain. Like Stack, Larry Layton was white and American — which apparently makes it difficult for some commentators to think of his action as an act of terrorism. In an ongoing Newsweek debate, senior editors are asking whether the label terrorist should be applied only to foreign actors. It’s intellectually muddled — what happens the next time Al Qaeda recruits an American to carry out a terrorist attack in the United States? Would that be terrorism — foreign actors were behind the mission — or not an act of terrorism, since it was an American who actually carried out the attack? The debate over whether Stack should be called a terrorist shows how problematic the definition of terrorism continues to be. I’ve long been in favor of using the consistent definition that terrorism expert Brian Jenkins utilizes: Terrorism is theater. The central difference between terrorist violence and other kinds of violence is that terrorists uses violence symbolically — the real target is not the person/building/institution being attacked but everyone who is watching. When you are angry at some group of people and you pick someone from that group at random to attack, you are engaging in terrorism, because the point of the attack is to send a message to everyone else in the group. Terrorists devalue their victims by turning them into props, and that is exactly what Joseph Stack did when he flew a plane into an IRS building. It did not matter to Stack which IRS worker he killed, just as it did not matter to Al Qaeda which Americans were in the Twin Towers on the morning of 9/11, because the real targets of these attacks were not the victims directly affected but everyone else who was watching.