Does the spread of nuclear weapons make the world safer or more dangerous? ‘Nuclear weapons in the age of terrorism’ considers this debate's relevance now and in the future. The debate is built largely on speculation and ambiguous historical experience. Nuclear weapons remain attractive to insecure or ambitious states. The prediction of mass destruction has so far proved false, but is that because of effective efforts to stop the spread of nuclear weapons, or is it just luck? Nuclear proliferation remains urgent. Optimists argue that if deterrence works, then there is less to be feared in the spread of nuclear weapons. Pessimists state that if it does not work, the international arena becomes more complicated and dangerous.