This paper discusses the likelihood that terrorists will detonate or threaten to detonate a nuclear device. The author considers whether terrorists are technically able to acquire a nuclear device, but finds that the real argument centers around terrorists' motives and goals: their desire to be watched exceeds their desire to kill large numbers of people. The author also finds that terrorists are limited by self-imposed constraints that derive from moral or political considerations: the belief that indiscriminate violence is immoral, the fear of alienating their perceived constituents, and the danger of creating a split within their own group. Circumstances may also erode the constraints: terrorists may become brutalized by long years of struggle; they may feel compelled to escalate their violence to keep the public's attention; and their perceived enemies may be an entire ethnic group. The author concludes that the use of nuclear threats by terrorists is not impossible, but also is not imminent or inevitable.