TWO things have been amply demonstrated in the six years that have elapsed since the collapse of the Berlin Wall: that communism is dead - and that it isn't.
It is a measure of the halting nature of the revolution that swept communist regimes from the face of Europe that, to a degree, both conclusions are valid.
''If you define communism as dictatorship, censorship, and sealed borders, then communism is dead as a doornail,'' says John Micgiel, director of the Institute on East Central Europe at Columbia University, in New York. ''But if you're talking about a closed system in which an economic oligarchy dominates in an undemocratic fashion, then communism is not dead.''
The ambiguities were underscored most recently in Polish elections, held last month. The balloting ended the presidency of Lech Walesa, who, as head of the Solidarity trade-union movement, led the rebellion that ended communist rule in Poland six years ago.
But diplomatic analysts say the return to power of old communists - like Mr. Walesa's rival and now president-elect, Alexander Kwasniewski - does not presage the return of the old communism epitomized by Lenin and Stalin.
''Even if communism comes back there will never be the same type of dictatorial rule,'' says Veljko Vujacic, of Harvard University's Center for International Affairs. ''What is possible is not totalitarianism but other types of authoritarianism, with at least limited freedom of press and elements of democracy.''
Freedom House, which annually ranks nations according to their polity, listed only five nations as ''communist one-party states'' at the beginning of the year: China, North Korea, Laos, Vietnam, and Cuba. There were 18 just before the Berlin Wall fell.
Except for Yugoslavia and Belarus, all the former Soviet bloc and newly independent states of Central Europe are ranked as ''formal democracies'' by the New York-based human rights group, even though several - including Poland, Lithuania, and Hungary - have elected parliamentary majorities of former communists.
Experts say the communist legacy in Europe is a political culture that is hostile to the excesses that have come with sudden market reforms and that is generally supportive of strong central government that redistributes national wealth.
''There are ingrained ways of thinking that survive,'' says Adrian Karatnycky, president of Freedom House. In practice, communism in its post-cold-war incarnation varies widely.
In countries like Hungary, Poland, and Slovenia, neo-communists who favor a welfare state, private property, and democracy are barely distinguishable from the social democrats of Western Europe or from the so-called ''new democrats'' in their own countries. Leaders like Poland's Mr. Kwasniewski, who was once a Cabinet minister in a communist government, are even eager to join the NATO military alliance - an alliance conceived half a century ago to contain communism and the armies of Soviet bloc nations including Poland.
In Russia and Serbia, on the other hand, communist politicians have acquired a mixed ideology that reminds some experts of the fascism of Germany and Italy during the 1930s: a belief in continued state ownership of some industries, a cartellized bureaucratic system, and a messianic strain of nationalism.
Mr. Karatnycky notes another coincidence that dramatically distinguishes the new communists from the old: In Russia and Serbia, the nationalism of communist politicians is linked to alliance with religious groups.
One example: Russia's resurgent Communist Party, headed by Gennadi Zyuganov, stresses a kinship with Ukraine and Belarus, some of whose Orthodox churches are under the Moscow patriarchate.
''In both countries, there is a desire to recapture lost territory that frequently coincides with the reach of parishes of Russian and Serbian Orthodoxy,'' says Mr. Karatnycky. ''Communist leaders pay homage to religious beliefs as a means of exploiting religious fervor.''
Paradoxically, the return of an ex-communist in Poland will mean the opposite: looser ties between church and state. Kwasniewski has called for strict separation of church and state in the new constitution and favors liberalizing restrictions on abortion that were advocated by the Roman Catholic church and enacted after communist rule in Poland ended in 1989.
One reason communism has survived in any form is that in most of the former Soviet-bloc nations there was no formal process of de-communization comparable to the de-Nazification of Germany that took place after World War II. One consequence is that many institutions with roots in the communist system, like trade unions and sports associations, have survived.
Many former communist leaders have also survived, largely because they retained control over industries, now semiprivatized, that were once bastions of party power. They have used durable political networks to maintain positions of power.
In the Russian context, communism has retained a degree of legitimacy because it is associated with two national achievements: the Soviet Union's emergence as a world power and its resistance to fascism during World War II, which has become a central part of the nation's mythology.
Russia's thriving Communist Party has also tapped successfully into a widespread distrust of the outside world - especially the Western world - which is blamed for Russia's halting progress since the collapse of the Soviet Union.
''In Ziuganov's opinion, the current plight of Russia cannot be considered an accident, but rather the logical consequence of a long-term plan concocted by Western intelligence services to destroy the Soviet state, and carried out with the intentional or unintentional support of their Russian collaborators,'' notes Mr. Vujacic. Neo-communism has also been nourished by the turmoil of transition. With market reforms have come economic disruption, crime, corruption, and uncertainty that, especially among older people and pensioners, have created a longing for the stability and predictability of life under communism.
''It's the longing for security that communism brought: that you could work and expect not to have to work very hard; that at the end of two weeks you would have a paycheck; that every year you would have a vacation,'' says Mr. Micgiel. ''Those perks are an attraction for those who have not made the adjustment'' to a market economy.
''Life under communism was unpleasant but it was safe and predictable,'' adds Charles Fairbanks Jr., a research professor at the Johns Hopkins Foreign Policy Institute. ''Now, nobody knows what will happen to them.''
Even so, few who lived under communism have any illusion that the economic and political system that grew out of the Russian revolution was anything other than a failure. A Marxist-Leninist party at the top of a one-party state is now the dream only of fringe groups. More typical is Russia's Zyuganov, who is eager to renationalize some but not all of Russian industries and is a reluctant advocate of multiparty democracy, private property, and freedom of religion.
''I don't think the pendulum can swing back to communism as the sole force in Russian society,'' says Karatnycky. ''But it may veer in a different direction, toward an ultranationalism bordering on fascism.''