On the morning of 9/11, Americans across the country witnessed al Qaeda’s terrorist attacks as appalling images that provoked shock at the slaughter, grief for the victims, and furor toward the perpetrators. Islamist radicals had succeeded in striking an intensely visceral blow. Even though the destruction was great, it once again became brutally clear that the power of terrorist violence derives not primarily from the physical damages it inflicts, but from the states of mind it provokes. This realization dominates our definitions of terrorism, which usually stress its intention to achieve victory by engendering fear. American reactions to 9/11, however, illustrate that we need to recognize the centrality of another emotion—outrage. While accepting the importance of fear in terrorist schemes, this article insists that to understand the dynamics of terrorism we should also grant that many of its most important gains come not by instilling fear but by inciting outrage.