Given the apocalyptic nature of nuclear weapons, how can states establish an international order that ensures survival while allowing the weapons to be used in controlled ways to discourage great wars, and while allowing nuclear technology to diffuse for civil purposes? How can the possession of nuclear weapons by a few states be reconciled with their renunciation by the majority of states? Which political strategies can best deliver an international nuclear order that is effective, legitimate and durable? These have been central questions in the nuclear age. This article suggests that the effort to construct such an order displayed the characteristics of an enlightenment project, with its emphasis on balance and rationality, the quest for justice and trust among states, the feasibility of instrumental regulation, and the attachment to hope and progress. With the Nuclear Non-Proliferation Treaty at its heart, it necessarily gave precedence to diplomacy and containment over preventive war. The reasons why this conception of nuclear order was discarded by its erstwhile champion, the United States, in favor of one bearing traits of counter-enlightenment, are explored. Its alternative strategy can now be declared a failure. Avoidance of a greater disorder depends on recognition that the problem of nuclear order is more than the problem of proliferation, or of non-compliance, and on recovery whatever the difficulties of the cooperative yet pragmatic sensibility that lay behind the prior approach to order.