JAN is no ordinary taxi driver. He speaks five foreign languages: German, French, English, Italian, and Russian. Jan, a silver-haired man with a PhD in economics from Prague's Karlova University, rose to become president of a foreign-trade company - until Soviet troops invaded Czechoslovakia on Aug. 20, 1968, crushing the liberal ``Prague Spring.'' Jan's Communist Party superiors soon summoned him for an interrogation. Two questions were posed: Had ``counterrevolutionary'' forces taken control of the springtime reforms enacted by Alexander Dubcek's communist government? And was it necessary to ask for ``fraternal assistance'' from the Soviet Union to save communism in Czechoslovakia?
``I could only answer `no,''' 64-year-old Jan recalls. ``I put my soul into those reforms.''
Like about half a million other Czechoslovaks, Jan was stripped of his party membership in a massive purge which ended in 1970. He was fired from his job, and replaced his suave gray business suits with the taxi driver's uniform of sneakers and jeans. Some 150,000 other Czechoslovaks decided to emigrate. In this country of 15 million, they were among the country's best and brightest, its academics, its artists, its scientists.
For Americans, with boundless faith in the future, it is hard to imagine an event that happened two long decades ago continuing to loom over a country. Anti-Vietnam war protesters have been able to rise into establishment positions. But in Czechoslovakia, the choice made back in 1968 determines one's place in society.
If you said ``yes'' to the Soviet invasion, you were spared. If you said ``no,'' you were banished into internal exile. Because Prague's present government bases its legitimacy on approving an invasion that crushed economic and political reform, it finds it impossible to copy Soviet leader Mikhail Gorbachev.
``We're still living with the trauma of 1968,'' says Karel Sys, director of the magazine Kmen. ``Until we deal with it, we will not be able to move ahead with perestroika and glasnost without fears of provoking a new crisis.''
Although some voices such as Mr. Sys's are calling for a reevaluation of 1968, the official line seems set in stone. As explained by Ivan Krempa of the Institute of Marxism-Leninism, the Prague Spring started out ``with the historic chance to renew socialism,'' only to veer out of control with the emergence of independent groups challenging the Communist Party's power.
``The process of renewal was taken over by those who didn't want socialism to get better,'' Dr. Krempa explains. ``They wanted to destroy socialism.''
Purged party members hold different memories. Unlike Poland, Czechoslovakia had a strong Communist Party, along with a tradition of sympathy for the Russians, fellow Slavs who had defended their country against Hitler's Germany. After World War II, the communists took 38 percent of the vote in free elections.
``We considered the Russians our friends, our liberators, the only one who could provide us with security,'' Jan recalls. ``The invasion destroyed this sympathy; that's the worst part, being betrayed by our friends.''
For the Czechoslovak reformers, another cruel irony is that Mr. Gorbachev is copying their 1968 cry of ``socialism with a human face.''
``Perestroika is the same thing as the Prague Spring,'' argues historian Jan Kren. ``Just like Gorbachev, we were fighting bureaucracy, encouraging individual initiative, promoting democracy.''
After the invasion, Mr. Kren hoped that many of the reforms could be salvaged. But in April 1969, Prague Spring leader Dubcek was forced from power. The massive purges followed.
Police harassment and prison terms, however, began only after 1977, when about 1,500 Czechs, most purged after the invasion, formed the human rights group Charter 77. Those who signed the manifesto were confined to menial jobs - night watchmen, stokers, window washers - which isolated them from contacts with others.
``We could not be lucky enough to become taxi drivers,'' says Jiri Dienstbier, a Charter 77 founder, who now toils as a stoker at a subway construction site. ``As taxi drivers, we could meet people and poison them.''
Jan, a more typical case, did not join Charter 77 and was not given a job designed to isolate him from human contact. Some doctors and scientists expelled from the party after the 1968 invasion were able to pursue nonideological research, although they were banned from positions of responsibility.
Children with purged parents also suffered. Either they could not enter university or, once admitted, found their paths to responsible jobs blocked. Jan's son was unable to finish his medical studies; now he organizes business conferences.
``That's the hardest thing,'' Jan says. ``It's normal that it affects you, its not normal that it affects your family.''
Like most of the purged, Jan retreated from politics into private life. He putters about his garden with his two grandchildren. This national mood is symbolized by the mass exodus of cars from city and town on Friday afternoons as urban Czechoslovaks head for small wood-and-stucco dachas that dot the countryside. ``You count on your family,'' he says. ``They're the only ones left.''
Jan's mood is sullen, resigned. His main interests are material, obtaining a few dollars or deutsche marks from tourists which he can use on Western goods. He doesn't dream of returning to his old prestigious job.
``It's too late to start over,'' he says. ``I'm too old.''