For some SALT critics, the gloom caused by the Soviet invasion of Afghanistan appears lightened by their belief that it shows that they've been right, that "the Russians can't be trusted" and that strategic arms control doesn't belong in the real world. Some suggest that this egregious Soviet conduct requires a drastic change in our foreign policy and new people to conduct it. Their mistaken assumptions are that SALT rest on trust, that SALT supporters blindly believed the Soviets to be a bunch of Boy Scouts and that pursuit of nuclear arms control is inconsistent with a sound defense policy.

I would be surprised if many who have dealt closely with the Russians are all that surprised by recent developments -- appalled, of course, and perhaps disappointed, but certainly not startled. Soviet incursions into neighboring states have had the periodicity of a plague of 12-year locusts -- Hungary in 1956, Czechoslovakia in 1968 and now Afghanistan.

Nor does this new proof that Soviet military power remains a threat to world peace mean that arms control efforts should be abandoned. Instead, the current crisis confirms the wisdom of trying, through strategic arms limitations, to lessen the risk that U.S.-Soviet confrontations will lead to mutual nuclear devastation.

Admittedly, it is uncongenial to try to reach agreements with a government that often sets its own international rules. But if we are to get anywhere in controlling nuclear arms, we must not continue to confuse SALT with detente, as do the advocates of "linkage." Detente connotes a lessening of frictions, of dangers to world peace. As detente fades, the urgency of arms control increases. We can only guess whether prompt approval of SALT II and active negotiations on theater nuclear forces and other Salt III issues would have forestalled the present crisis. But we should know that without the Salt II treaty we are now less secure. Detente should remain a long-range goal. But control of strategic nuclear weapons is an immediate necessity.

Disputes about Cubans in Africa and about Soviets in Cuba and Afghanistan show that the differences between the United States and the Soviet Union are serious and continuing. We have regrettably little in common. What we do share, and what makes nuclear arms control feasible, is a common interest in survival and in avoiding nuclear weapons proliferation. Because of this common interest, SALT negotiations could start the year after Soviet force ended the Prague Spring and while Soviet-supplied weapson were killing Americans in Vietnam.

Whether the present Soviet aggression is a response to a particular concern or part of ann overall design does not affect the seriousness with which it must be treated. No state is entitled to seek perfect security for itself at the sacrifice of that of another. And if conduct of this kind goes unchallenged, a limited original purpose may be converted into something more ambitious.

The Soviet leadership seems to be losing sight of the cardinal rule of superpower competition -- that neither side improves its own security by endangering that of the other. Pursuit of a plan to bring the Persian Gulf states under Soviet control would constitute a direct and massive threat to our interest. In contrast, we have very wisely made it clear that our new relationship with the People's Republic of China will not evolve in a way that threatens the security of the Soviet Union.

At best, the world is in for a troubled time. At worst, the crises will be played out with no controls over nuclear weapons, with each side trying to gain greater strategic nuclear strength, and thus posing a greater threat to the other's security. For both, the cause of national survival would be best served by prompt entry into force of the SALT II treaty and renewed efforts to obtain more sweeping controls on nuclear arms. But "linkage" here seems destined to conquer logic.

Recognizing that we cannot trust the Russians (and with no reason to believe that they trust us), we still need to avoid the immense risks of further nuclear escalation. The real world needn't include nuclear anarchy.

In his State of the Union address, President Carter cited the need "in a time of great tension" to observe the mutual constraints of Salt I and SALT II. In fact, since October 1977, when the SALT I Interim Agreement expired, there have been no formal controls over offensive nuclear weapons. Each country then announced separately that it intended to do nothing in contravention of SALT I limits. These undertakings have been honored.

Important SALT principles have been fully worked out and could be implemented and verified without a ratified treaty. (The U.S.-Soviet treaty limiting nuclear weapons test to yields of 150 kilotons is treated as binding although the Senate has never acted on it.) A U.S. statement could detail our intention to abide by these key principles provided that the Soviet Union does the same.

Continued in the reciprocal restraints should be the freeze on the ICBM silos, the most deadly and yet the most vulnerable of the nuclear weapons delivery systems. In matching statements, the sides would commit also to freeze the maximum number of multiple independently targetable reentry vehicles (MIRVs) on any type of existing missile, to flight-test no more than one new ICBM and to limit the new missile to 10 MIRVs. Of crucial importance, each country should state also its intention to refrain from concealment measures or other interference with national technical means of verification.

This approach would leave us free to proceed as planned with the modernization of each part of our nuclear deterrent triad. It would, of course, leave us far short of the benefits of the full SALT II treaty, such as the-equal ceilings and sub-ceilings that would require actual reductions in existing Soviet forces, and the chance for speedy negotiation of tighter controls.

As with a formal SALT treaty, there could be no guarantee that the Soviets would live up to their commitments. But our national technical means of verification would tell us if they were not, and would also tell us if they were interfering with those means and trying to conceal nuclear weapons developments.

To support SALT is not to suggest that it is the panacea for all international problems. And to continue to pursue strategic arms control is not to condone Soviet misbehavior. But the new realism doesn't require that we emulate the Roman andabata , who was thrust into the combat arena fully armed and armored, but sealed sightless in his helmet.