HERE is a hypothesis worth testing: Mikhail Gorbachev may be a Soviet leader with whom the United States could work to produce fundamental, constructive changes in the nature of the superpower relationship. Among some American conservatives, it is an article of faith that the Soviet communist system cannot evolve into something more benign. Soviet totalitarianism, these people believe, cannot change peacefully; nor can the Soviet Union tolerate normal relations with a democratic, capitalist superpower like the United States.
The United States cannot afford, however, to found its foreign policy upon an article of faith. History has surprised too many people too often for Americans to regard their beliefs about what is possible as anything more than hypotheses.
If a transformation of US-Soviet relations were possible, its importance could hardly be overestimated. ``Star wars'' dreams notwithstanding, security in the nuclear age cannot be gained through the technological fix of defensive systems. Our security, rather, is a political challenge: Only when Soviet nuclear weapons threaten us as little as British warheads do today will we really be secure.
Beyond that, the intense superpower struggle is a major obstacle to man's dealing effectively with pressing global problems like environmental deterioration and grinding poverty. Not only do tremendous material resources go into the arms race, but governments preoccupied with their immediate national security give scant attention even to grave long-term challenges. And it is often superpower competition that makes regional conflicts even less soluble than they would otherwise be.
Improvement in superpower relations is obviously desirable. The issue is whether it is possible.
What reason is there to believe - since the Soviet Union remains a repressive, militaristic, imperialist society - that Mr. Gorbachev's leadership might create an opportunity for a fundamental amelioration of world tensions? The question, rather, is if he were that kind of leader, how would he act upon coming to power?
Would he not show greater concern for the internal health of his own society? Would he not seek to root out the corruption in the Soviet political system, and to make that system more responsive to popular will?
Would he not strive to overcome the Soviet system's ingrained unwillingness to confront its shortcomings, allowing more criticism in domestic discussions and telling the world more about Soviet mishaps (as at Chernobyl, and the accident last year with the Soviet submarine)? Would he not seek a way to end his country's occupation of Afghanistan? Would he not seek to deescalate the arms race, and ease chronic tensions with his great neighbor to the south?
All this, of course, is what Gorbachev has been doing in his brief tenure. A great deal more needs to be done before the Soviet Union could be a less threatening presence on this globe. But it was not Gorbachev who ordered the invasion of Afghanistan, nor he who brandished the Soviet sword over Poland in the bright days of Solidarity.
Changes take time, and no sane Soviet leader, whatever his intentions, would seek to dismantle overnight the total apparatus by which the Kremlin for 70 years has sought to protect its power.
Even as un-starry-eyed an observer as Henry Kissinger has been impressed with the pace and directions of the changes Gorbachev has ushered in.
Of course, time may prove the conservatives right in their assumption that Gorbachev is but a more charming version of the same implacable enemy.
But the assumption can be self-fulfilling. Just as the Soviet invasion of Afghanistan gave former President Carter's accommodating approach a bad name and helped usher in the age of Reagan, so also might American implacability doom a truly constructive Soviet leader, or compel him to return to the old ways of confrontation.
It would, conversely, also be dangerous to assume that Gorbachev is what we would like him to be.
But there are ways of testing the hypothesis which do not endanger our security. One is to make a serious effort at arms control. Another would be to seek with the Soviets better ``rules of the game'' in our global interactions, and to explore with them possible ways to reduce tensions in places where we now fight each other through proxies or clients. A third would be to undertake cooperative endeavors for solving less political global problems, such as hunger and disease, and threats to the biosphere.
It is, regrettably, not likely that the Reagan administration will test this crucial hypothesis. In the best of times, its ideological rigidity might well have prevented it. Now - as a lame-duck administration becomes still further hobbled by the injuries from the Iran-contra affair - the chances of this administration's initiating imaginative approaches to diplomatic challenges seem even more remote.
But the race for president in 1988 is already gathering momentum. The nation now has a chance to choose its direction for the years after Reagan. As we look over the candidates who present themselves for our consideration, one important question we might ask is: Which of these people possesses the imagination and subtlety to test the Gorbachev hypothesis?
Andrew Bard Schmookler is the author of ``The Parable of the Tribes; The Problem of Power in Social Evolution.''