Not every bombing, no matter how many civilians are killed or how terrifying it is, is terrorism. The Boston Marathon atrocity on Monday afternoon may qualify or it may not. Since the discourse around terrorism in the U.S. is an exceptionally fraught one, here's how to think through the issue.
Terrorism is not just violence aimed at civilians. Terrorism is violence aimed at civilians with a political objective — most often, designed to cause a spectacle.
The Boston Marathon attack brought violence against civilians: three are dead and over 150 injured, several critically. The bombs were placed near the marathon's finish line at Copley Square, where banks of video cameras and spectator smartphone caught the race's end, so it's safe to say it caused a spectacle. We don't yet know whether it carried a political objective, and that's the crucial criterion.
No one — group or individual, foreign or domestic — has taken responsibility for the attack. If and when someone or some group does, it may not be definitive: as last September's Benghazi attack showed, claims of responsibility are not always genuine. A press conference on Tuesday morning by the Boston investigative team underscored that law enforcement is just beginning to understand what happened 18 hours ago.