A MAN stands briefly on the stage of history. From a childhood during his country's Terror, he was recruited to manage the system of Terror, and emerged not quite a hero, but at least a seemingly sincere reformer. And finally, as has happened to reformers before, it seems that Mikhail Sergeyevich Gorbachev is being swept away by the forces that he himself unleashed.What are we to make of this man's career? How will he be judged by the historians of the future? He looked impressive and innovative during much of his career at the pinnacle of Soviet society. The 1987 agreement under which the world's two nuclear megapowers agreed to dismantle all their intermediate-range nuclear weapons stands as his greatest achievement. The INF agreement showed clearly that, on both sides, the terrible hostility of the early 1980s had been transcended. The personality, policy smarts, and persistence of General-Secretary Gorbachev were unique resources that he used to persuade both sides' hard-liners to engage in that dispersal of tensions. Two years after the conclusion of the INF agreement, Gorbachev's landmark decision not to use the Red Army to prop up Soviet power in Eastern Europe underscored the distance he had traveled from traditional Soviet thinking. At a time when the whole world needed creative diplomacy to save us from the craziness of continuing the cold war, Gorbachev was the one who provided it. He reframed the relationship between Moscow and Washington from the deadly arms-racing involved in building an ever more powerful "deterrent" into an appreciation of the fact that in today's world security is truly a cooperative affair. Did Gorbachev engage in this reframing because he was a visionary, or because he sat in the one seat on earth from which the bankruptcy of the Soviet system was clearly evident? Maybe, under this latter explanation, the decision to change the terms of the relationship with Washington was less heroic and more like stark necessity? We should remember, though, that in the few years before Gorbachev came to power, three predecessors in succession had sat in his seat, and none gave evidence of having reached the same conclusions. Or maybe, Gorbachev's reframing of relations with Washington was intended as a step toward freeing up resources to revitalize the Soviet system? The true mix of motivations that originally inspired him will probably never be known. But by the time he had launched the associated domestic policies of glasnost and perestroika, revitalizing the Soviet system proved an impossible goal. And yet he continued to strengthen the new detente with the West. Thank goodness he did. If we here in the United States had not had Gorbachev prodding Presidents Reagan and Bush, challenging them to rethink the foundations of the global power balance, at what stage would they have spontaneously undertaken this rethinking on their own? We might still be locked into the massive defense-spending binge that marked the mid-'80s. And how would the almost inevitable breakup of the Soviet empire have looked if a Brezhnev-type figure were still clinging to control in the Kreml in? We are left with a picture of Gorbachev, once he came to power, as a true innovator in foreign policy. His appearance as such was all the more notable because the system which incubated him was not one in which innovative thinking was encouraged. Nor had he himself, prior to acceding to power, given any signs that he was inclined to buck the system. Andrei Sakharov, Gorbachev was not. But, to his credit, after he came to power he finally gave public (if tardy) recognition of the greatness of Sakharov's t hinking. Ultimately, however, as Tip O'Neill was fond of saying, all politics is local. And Gorbachev found himself unable to use the personal skills so successful in foreign affairs to deal effectively with chaos at home. (Is there a parallel with Bush's situation?) Given the scale of the problems that the peoples of the former Soviet Union face, there can be no room for praise or blame for Gorbachev on this score. A man stands briefly on the stage of history, then takes his exit. Let it be a graceful one, marked by our applause. But the peoples whom he once ruled will need a lot more than applause. If ever the term "constructive engagement" had meaning, then that is what the formerly Soviet peoples will need from the international community in the months and years ahead.