On a glorious, sunny day in Berlin, I found myself in the dimness of the Stasi museum -- a two-story concrete building that exhibits the tools that East Germany's secret police used to spy on most of its citizens' lives.

I came to this museum not out of perversity, but because I was impelled by the German movie "The Lives of Others," which just won the Oscar for best foreign film.

It offers a chilling and emotionally powerful portrait of Stasi surveillance of a fictional writer and artist couple. Directed by a young West German named Florian Henckel von Donnersmarck, the movie is drawing huge crowds in Berlin, even though it's 17 years since the fall of the Berlin Wall.

I believe the film also has significance for Americans at a post-Sept. 11 time of heightened concern over security surveillance in the United States.

No, I don't think we are headed toward a Stasi regime in our country. But East German history reminds us of what happens when there are no checks on government power.

Germans tell me this is the first film that provides a realistic view of the suffocating surveillance methods of the Stasi. By 1989, about 92,000 secret police and 170,000 informers were taking compulsive notes on their victims in a country of only 16 million; they had produced paper files that, laid end to end, would stretch 173 kilometers.

Most of these files were salvaged by East German opposition groups before the Stasi could destroy them. I witnessed one of these citizen takeovers in Leipzig in November 1989. Twenty-four local men and women, drawing courage from a huge anti-communist demonstration in the city center, demanded that the Leipzig Stasi let them into its headquarters. They took me in with them. I will never forget the faces on the secret police officials who clearly wanted to arrest us, but understood that their world was collapsing.

Standing in the Stasi museum, it is easy to understand that pent-up anger. The secret police invaded every aspect of people's lives (although most East Germans had no idea of the extent of the surveillance until after the wall fell).

You can see exhibits of the special tools they used to enter people's homes and the tiny bugging devices they installed behind light switches. You can observe a row of yellow cloths, in glass jars, that were used to collect body odor samples by swabbing chairs in kitchens or studies. You can look at rows of old-fashioned tape reels that collected data from bugged phones, and photos of refrigeration trucks that parked in residential areas with surveillance cameras.

Andreas Shultze, the spokesman for the federal authority that maintains the files, himself was punished and spied upon as a conscientious objector in East Germany. I asked him whether he worried about a new era of government intrusion. "Since 9/11, I've asked myself over and over whether we could go back," he replied. "In special situations it might be legitimate to leave the way of freedom, but we have to keep the opportunity for a way back. If a special situation becomes a normal situation, then begins the problems."

This is another way of saying that democracy needs checks and balances to limit executive power. A glimpse into the unchecked world of the Stasi reminded me that those limits define the difference between their world and ours.

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