Terrorism is, to a significant degree, a problem of perceptions and the associated difficulties with credible commitments. Sometimes it is possible to distinguish among competing hypotheses about terrorism by changing our own behavior. This is precisely the process that led to progress toward peace in the Middle East and in Northern Ireland. Our examination of terrorism in this chapter has highlighted how beliefs can promote policies that produce unintended consequences. Only through a change in behavior—that is, through a calculated risk—is it possible to break, or at least diminish, the cycle of terrorist violence. But we can¬not blithely call for such a gamble without considering the real risks and costs associated with it, including one side’s reneging on its commitments and, if counterterrorism efforts fail, an increase in violence implemented by the remaining, more extreme terrorists who acquire additional resources when more moderate factions compromise with government. By improving our understanding of how perceptions and strategic conditions influence choices, we can help foster progress toward peace throughout the world.