MOSCOW -- The Soviet Union, which built an empire of Communist satellite states in Eastern Europe with zeal and determination over four decades, now seems to be watching its breakup with surprising equanimity--and even approval--as one ally after another embarks upon a course of political reform that could take it out of Moscow's orbit.

When Poland prepared to install the first non-Communist government in Eastern Europe since the early days of the post-World War II era, Soviet President Mikhail S. Gorbachev telephoned Mieczyslaw F. Rakowski, the first secretary of the Polish United Workers Party, at a crucial moment with the advice necessary to reach a breakthrough agreement with the Solidarity opposition.

When the Hungarian Socialist Workers Party, a product of Soviet military occupation as much as of ideological evangelizing of the region, transformed itself this month into a party of social democrats in the Western European mode, Soviet commentators applauded the move as a progressive reform that Moscow itself might study.

And when East Germany was slow in assessing mounting street demonstrations there and a surge of emigrants in recent weeks, Gorbachev tartly reminded his allies in East Berlin that "those who are late are punished." East German leader Erich Honecker, 77, retired 10 days later amid expectations that his nation, one of the staunchest of Soviet allies, also was about to plunge into the maelstrom of change in Eastern Europe.

In the conventional wisdom of Western political commentators, all this adds up to the failure of socialism. The Cold War is over, they have argued, and capitalism is the clear victor. They believe the Soviet satellites, those "captive nations," are finally spinning out of Moscow's control.

Yet for Gorbachev, the changes constitute the reformation of socialism, not its collapse--and in this renewal he finds political strength, not weakness, and a process to be encouraged, not stifled.

Although some in Moscow are uneasy about the developments in Eastern Europe--Soviet newspapers have published letters expressing fear for the country's security if Poland or Hungary "go West"--Gorbachev appears to view the changes as part of his broader vision for the reform of socialism.

Speaking here this week with Willy Brandt, the former West German chancellor, Gorbachev acknowledged that some see developments in the socialist countries as "the fiasco of socialism, of the very idea of socialism."

"We are striving to find socialism's optimum response to the challenge of the times," he told Brandt, who is now president of Socialist International, made up of social democratic parties. "The further development of socialism should be visualized in the context of the overall development of contemporary civilization. It should pool all the benefits that can be found in the experience of other societies and other political movements."

This, along with an intense preoccupation with its own domestic problems, probably explains the Soviet Union's calm acceptance of developments in Eastern Europe that in the past would have precipitated international crises.

"A couple of years ago, this would have interested me a great deal," a Soviet official remarked to a Western diplomat this week as the Hungarian Parliament amended the country's constitution to end Communist rule there. "But now I am more interested in trade with South Korea."

Yet set against the patterns of postwar history, the changing relationship between Moscow and its allies--and its implications--is indeed dramatic and reflects the fundamental political and economic shifts under way throughout socialism.

In strategic terms, the Soviet Union is more than loosening its iron grip on Eastern Europe: Moscow is consciously promoting the reintegration of the continent, in part from the recognition that this, better than a military alliance, will ensure its own security and in part to assure itself of a place there in the 21st Century.

The Soviet Union, anticipating both that the East-West confrontation will fade and that the North Atlantic Treaty Organization and the Warsaw Pact soon will begin reducing their huge standing armies, launched a discussion this month on the future of the Warsaw Pact as a political rather than a military grouping. Equally to the point is a debate within Comecon, the socialist trading bloc, about its future as the much larger European Community integrates its economies.

And what Soviet reformers say they hope will emerge around Moscow will be a "socialist commonwealth," linking the Soviet Union with other socialist countries, transforming the Soviet Union and its constituent republics into a far more federal system and developing ties with Europe's social democrats.

In ideological terms, the present Soviet leadership sees "common human values," not class struggle, as the basis for progress. The ideals of socialism remain, but their achievement is now seen as taking far longer. So uncertain is Moscow now about its political philosophy that there is even a debate here about whether the Soviet Union is socialist, that perhaps it has never fully corrected the policies of the dictator Josef Stalin.

"What you see is not a failure of socialism, but of Stalinism," a Soviet political scientist said this week. "Why should we defend Stalinism?"

Hungary and Poland consequently argue, with great effect, that the establishment of their one-party socialist governments after World War II was a political error by Stalin that should be corrected. If the Soviet Union is unsure what constitutes socialism, East European leaders now ask, how can their countries be criticized for political and economic experimentation?

In political terms, Gorbachev is looking for allies--other leaders who see the achievements and flaws of socialism as he does, and who also see in it potential as a political and economic system and share his pragmatic brilliance. He believes he has found some kindred spirits in Hungary and Poland and thought he had in China with Zhao Ziyang, who was subsequently removed as general secretary of the Chinese Communist Party.