A summit to build on

THE end of the fourth and likely final summit between President Reagan and Soviet General Secretary Mikhail Gorbachev marks a welcome victory for practicality and realism in the conduct of United States-Soviet relations. The summit provides a stable foundation on which Mr. Reagan's successor can build bilateral ties. When Reagan came to power, US relations with the Soviet Union were souring. For a time, the pendulum seemed to swing from one extreme view to another.

On one side lay the naivet'e that prompted President Carter to say, ``My opinion of the Russians had changed more drastically in the last week than even the previous 2 years'' when the Soviets invaded Afghanistan in December 1979. On the other, vitriolic anti-Soviet rhetoric permeated the early years of Reagan's first term - providing a counterpoint to the heady hopes surrounding detente during the mid-1970s.

In an irony of timing, the Reagan presidency would inadvertently turn the tables on the Soviet leadership. Leonid Brezhnev's tenure overlapped five US administrations. The slow pace of negotiations on arms control, for example, was often interpreted as Brezhnev's attempt to see if he could use the deadline of presidential elections to get a better deal from the next administration. As the first President who will have served two full terms since Eisenhower, Reagan has overlapped the rule of four Soviet leaders.

In Mr. Gorbachev, Reagan has found a Soviet leader it could do business with, to borrow British Prime Minister Margaret Thatcher's phrase.

But for relations to improve, the Soviets needed a Reagan administration they could do business with. That was a difficult prospect when conservative hard-liners occupied key administration posts. Once the hard-liners began to fall away, the prospects brightened for more realistic US negotiating positions at arms control and other talks.

By traditional measures, the Moscow summit's achievements are modest: expanded cultural exchanges; some confidence-building measures in the area of arms control; and agreements on the peaceful uses of outer space, for example.

But the summit is nonetheless valuable in laying a stable foundation for future US-Soviet relations and for the example it sets as an alternative to confrontation.