Spring always brings new blossoms, but 20 years ago, spring brought to China an unprecedented flowering. In hundreds of cities, citizens took to the streets in peaceful protests to demand freedom, government accountability and an end to corruption -- and the government, once among the most repressive on earth, stood by and let them.

It was an intoxicating moment that didn't last. By the morning of June 4, the government had reversed course, sending the army to crush the long-running student demonstration in the capital's Tiananmen Square, leaving hundreds dead, and the Beijing Spring was over.

Since that day, China has undergone such a broad transformation that it is almost unrecognizable. The economy has opened up to markets, private property and foreign trade. Living standards have soared. The government that once preached world revolution now provides credit to sustain American consumption. Chinese students go abroad to attend universities in bastions of capitalism.

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But the bloody events of 1989 are still a live issue in China. Last month brought forth the posthumous secret memoir of Zhao Ziyang, the Communist Party chief removed because of his sympathy for the protesters. In it, he denounced the crackdown as "a tragedy to shock the world" and said his country deserved "a state more suitable to a democratic society."

Naturally, the book is not available in China, except to those who elude Internet censors. The government has gone to great lengths to suppress any discussions of the anniversary, even blocking Internet services like Twitter and Flickr.

The sensitivity of the topic, even though most young people know little or nothing about it, is a measure of the impact the 1989 protests had on the people in power. Even today, it troubles their sleep.

But the episode was not what it initially appeared to be: the end of China's evolution toward a more liberal system. It was only an interruption of that process. In the aftermath, the Chinese Communist Party grasped that it could hold onto power only by delivering a better life to its people, which it could achieve only by loosening its grip on their lives.

By now, it has had to abandon its own ideology and invoke Western principles. In his 2007 speech to the national party congress, President Hu Jintao used the term "democracy" some 60 times, while calling for the government to be more open, accountable and limited.

This declaration should not be taken on faith, but it's not just lip service. Democratic elections have become common at the village level. The government clearly strives to take public sentiment into account in making policy. When an earthquake devastated Sichuan province a year ago, foreign reporters were allowed unprecedented freedom to cover the aftermath. A system of law is emerging.

The average person now enjoys far more personal freedom and independence than the Chinese of previous generations. "I am often surprised by how accustomed people in China have grown to expressing political opinions in private, in ways that would have been unthinkable 10 or 20 years ago," Patrick Chovanec, a professor at Beijing's Tsinghua University, told me.

Chinese blogs and websites don't shy from social ills and government abuses, and some 300 million people have access to the Internet. On a recent trip to China, I found access to the Human Rights Watch website blocked. But when I searched U.S. newspapers for criticisms of the Chinese government by the group, they were freely accessible.

The demise of totalitarianism is apparent from the willingness of ordinary Chinese to express their discontent. Last year, there were 120,000 "mass incidents," such as strikes and demonstrations, and the pace has accelerated this year.

There are, however, still grave risks in challenging the government. Freedom House, the New York-based human rights organization, says China's labor camps and prisons hold hundreds of thousands of religious and political prisoners. In a basic way, the regime responsible for the Tiananmen Square tragedy has not changed.

But as societies grow richer, history indicates, they invariably become democratic, as Taiwan and South Korea did not so long ago. China's rulers clearly fear they will eventually fall to the same iron law.

In light of the government's poor human rights record, genuine rule by the people may seem as distant today as it did on June 4, 1989. But if there is one safe assumption, it's that the crucial chapters on Chinese democracy are yet to be written.