For individuals ready to engage in terrorism for reasons of passionately held ideology or deeply felt resentment, the force of conventional, social morality may be weak and even the fear of punishment may have little impact. The processes of law enforcement alone are not relied upon to maintain law and order in the case of terrorist bombings because of the degree of harm that may be done before any arrest is made. There are other ways to prevent the terrorist event. Prevention is targeted if intelligence has enabled the government to identify the time and place of a proposed attack or even to identify the individuals who are planning a terrorist strike. The steps of targeted prevention are to isolate the target from the terrorists or sabotage their plans; then arrest the terrorists as soon as all the possibilities for determining their plans, associates, and supporters are exploited. The crucial ingredient is intelligence. The purpose of untargeted prevention is to make it more risky and difficult to carry out a terrorist act and thereby reduce the level of terrorist events by increasing the time, expense, and effort. To accomplish his ends, the terrorist needs to (1) locate the target, (2) get to it, (3) with the needed associates, (4) with the necessary information, equipment, and facilities, and (5) with an expectation of enough safety to justify the risks. Prevention of terrorism requires depriving the terrorist of one or more of these five conditions. In the case of catastrophic terrorism, such as the use of nuclear, biological, or chemical weapons, systematic efforts at prevention are essential. These efforts include denying resources and information to the terrorists, and denying them the support they need from others.