WHAT'S next? It's dangerous to get caught up in the euphoria of a summit or a historic high in the stock market - just as it's dangerous to be trapped in paralyzing anxiety over mass demonstrations against Pershing 2s, ``evil empire'' talk, or a stock market crash. The best remedy for such emotional swings is to review what brought us to the peak or trough. And then take a hard-headed look at what's likely to come next.
It's quite clear that Ronald Reagan and Mikhail Gorbachev would like to arrive at some version of a ``grand compromise'' by next spring or summer. Such a grand compromise would involve an offensive/defensive trade-off. It would barter (1) deep enough cuts in Soviet (and US) long-range nuclear missiles to make a Soviet first-strike victory too risky, in exchange for (2) sufficient restraint on the pace of US ``star wars'' strategic defense to prevent a breakthrough to a shield for a possible US first strike.
Mr. Gorbachev and Mr. Reagan, and their advisers, do not yet agree on terms for such a grand compromise.
It's also quite clear that in coming months the American Senate will be concentrating as much on the wisdom of a future grand compromise (what in show-biz jargon would be called a major, major deal), as it will spend looking back at the quite major enough deal it will be asked to ratify - elimination of midrange nuclear missiles in Europe and Asia.
It is almost as clear that if Ronald Reagan wins ratification of even the first of these deals, his successor - of either party - will be broadly protected in regard to American public opinion to explore further deals with Gorbachev.
And that makes it likely that Reagan's jilted opponents on the Armageddon far right will resort to two tactics to forestall both a grand compromise and further bargaining beyond it. One of these tactics is already apparent: the savaging of Reagan as a man carried away by utopian dreams. The other tactic is likely to be an increase of claims the Soviet Union cheats on agreements. That will create considerable pressure for visible, precise execution of verification agreements at Soviet and US nuclear missile plants.
The grand compromise sounds climactic and final, a peak to end all summits. It isn't. Such a compromise on long-range weapons adds to European pressure for further agreements on verifiable cuts in conventional forces and chemical and biological weapons.
America's European allies would like to use the leverage of Moscow's desire for the grand compromise to force progress on the conventional arms front. Gorbachev's military advisers have probably argued strongly against conventional-force reductions. In the longer run, labor shortages and civilian resource needs could make some demobilization attractive. But in the shorter run, Gorbachev's industrial restructuring could lead to civilian unemployment. And Politburo strategists simply may not want to deal on conventional arms, where they hold a strong advantage.
Shorn of the complexity and uncertainty which always shroud future war capability, what the Western and Eastern alliances want is protection against a successful first strike via either nuclear missiles or conventional weapons. Because of geography, Western Europe's concerns about such conventional warfare are naturally greater than America's.
(Japan, covered by Washington's nuclear umbrella and subject mainly to conventional Soviet sea and air power, is less concerned. China has taken the calculated risk of cutting its conventional forces unilaterally by 24 percent, knowing a Soviet invasion from Siberia would stretch Moscow's supply lines, open a battlefield quagmire, and perhaps risk US alliance with Peking.)
Moscow's Afghanistan experience provides the Western allies some relief from anxiety about a preemptive Soviet conventional strike. So may the restiveness of Poland and other Warsaw Pact allies of the USSR.
Of all these matters, only the grand compromise seems possible on Ronald Reagan's watch. But that doesn't end the question of what's next. Gorbachev and President X will have a potentially full agenda in 1989 and beyond if events don't sour the new d'etente.
(It should be noted here that the hopeful Eisenhower-Khrushchev ``thaw'' plummeted with the U-2 shoot-down. The Kennedy-Khrushchev test ban and outer-space cooperation eroded with assassination and Vietnam. The Nixon-Kissinger-Ford-Brezhnev d'etente ended with differences of interpretation and with Soviet power plays in Africa, Afghanistan, Cambodia, and Central America.)
On the longer range agenda is the aforementioned conventional, chemical, and biological arms control. Also trade and technology transfer, linked to human rights and Jewish emigration.
If trade and technological access don't increase, Gorbachev's plans for economic rebirth may be in even greater trouble than they are now. His present situation is both more difficult than most Westerners realize, and not as dire as it has appeared since his prot'eg'e Boris Yeltsin was first attacked in August.
What the Yeltsin ouster indicated is that Gorbachev, like Deng Xiaoping in China, must tack against his own reform plans when he runs afoul of entrenched conservative interests. He may, in fact, have to undermine his own reforms more gravely than did the Chinese reformer after the fall of his prot'eg'e Hu Yaobang. But the Politburo old guard still needs Gorbachev as spokesman and symbol as much as a conservative college of cardinals has often needed a moderate pope.
One final note about what's next: Gorbachev has not fully picked up on the meaning of his fourth key word, interdependence of nations. The other three - openness (glasnost), restructuring (perestroika), and sufficiency in nuclear deterrence - have been broadly examined. But the US should be prepared for more initiatives derived from interdependence.
Soviet support for the United Nations as a place for settling disputes is already one such initiative. It would not be surprising to hear Gorbachev launching others. One might be leadership on problems of the world's atmosphere: the greenhouse effect, rain-forest cutting, and rising oceans. Another might be a revival of the idea of a joint US-Soviet Mars mission in the next century.
Earl W. Foell is editor in chief of The Christian Science Monitor.