The world has been remarkably successful, so far, in preventing the spread of nuclear weapons. Six countries demonstrably have them and two others, South Africa and Israel, either have them covertly or are very close to it. But there are perhaps three dozen more that possess the industrial capability to make them. Restraint depends on an international consensus that is unusually broad, but not unanimous. Every five years most of the world's governments meet to review progress under the Nuclear Nonproliferation Treaty that went into effect in 1970, and the third of these review conferences has just opened in Geneva.

These conferences influence the atmosphere in which politicians make decisions about weapons. Since nonproliferation depends on cooperation among governments, most of it voluntary, atmosphere makes a crucial difference. Both of the previous conferences were devoted mainly to quarreling between the nuclear powers and the Third World. It's inevitable that the quarrel will be revived in Geneva over the next several weeks. But it would be a great misfortune, and a waste of an important opportunity, if this conference were to turn out like the one in 1980 that never got to anything else.

The nonproliferation treaty is inherently discriminatory in the sense that it establishes one set of rules for the countries that have nuclear weapons and another for those that do not. To reconcile that difference, the treaty proposed a couple of bargains. The countries with nuclear technology were to share it with the others for generating electricity as long as they renounced its military uses. That part of the agreement has worked well, with a few notorious exceptions. But, unrealistically and unwisely, the original treaty also committed the nuclear powers to pursue arms control -- not only nuclear arms control but "a treaty on general and complete disarmament."

To many of the small countries, the nuclear powers' failure to make much progress there has become an intractable grievance. It's hardly a trivial one, but U.S.-Soviet arms control is a separate subject from nuclear proliferation in the rest of the world, and it needs to be kept separate. To entangle them, to make one dependent on the other, improves no one's security.

Security is, after all, the issue. The right question is whether possession of nuclear weapons by any additional country would actually improve even its own security. The review conference in Geneva will certainly address the shortcomings of the countries with the largest armories. But its real contributions to security are more likely to lie in the painstaking and undramatic work of reviewing sources of supply, strengthening the procedures for monitoring reactors, and improving the audits of the world's expanding nuclear economy.