THE THEORY of detente, as spun out first by Henry Kissinger and as practiced now by Jimmy Carter, is to draw the Soviet Union into continuing negotiations across the whole range of East-West issues and matters of common concern. By this process of cummulative interaction, it is hoped, the Russians will come better to believe that their own best interests lie in a deepening of East-West engagement, rather than in lone, undisciplined freewheeling. President Carter seems himself ready to accept a similar commitment to submit to the bargaining process some questions that the United States formerly reserved the right to decide on its own.

Not everyone is equally ready, of course, to yield up freedom of action for the uncertain fruits of Soviet-American cooperation. On the particular question of sales of conventional weapons, however, the case is strong for the sort of formal dialogue that, the administration reports, is about to begin. In the absence of explicit East-West consultation, Washington and Moscow now ship billions of dollars, worth of arms a year to allies, established clients, the internationally newly rich, and assorted targets of political opportunity. They use sales not just to care for their and their allies' security, but also to make money and lower the cost of their own procurement, and to extend their own influence or presence or prestige. Some of these transfers are reasonable, some are not. Discriminating between them needs to be regarded as a sensitive diplomatic act affecting not only the supplier's relations with the recipient but with other great power as well.

The situation is bad but not unrelievedly bleak. Americans and Russians sometimes recognize that, by shipping arms abroad, they export a capacity for independent action and troublemaking. Moscow, for instance, decided in and after the 1973 war in the Middle East not to grant Egypt's every weapons request. For this politically costly example of restraint it has received, in arms-control terms, scant credit. Right now, Washington is turning aside Somalia's call for arms. It is willing to risk losing immediate favor for the sake of calming down the Horn of Africa as a whole. These are the kinds of choices that a conventional-arms dialogue would presumably nurse along.

Some officials suggest that it is a victory of sorts to win Soviet agreement to enter arm-sales talks. This line of thinking is, at best, indiscreet. The impulse of Soviet conservatives, as their American counterparts, is to regard Soviet-American negotiations, in any forum, as a trap. Americans should not be encouraging this suspicion. There is no assurance that these talks, and others, will succeed. But if they cannot be described and conducted in a way that serves mutual advantage, they will surely fail.