Beijing ? You have heard of pingpong diplomacy — the exchange of table tennis teams that was the opening move in the series of encounters that ultimately led to the United States and China resuming formal relations a quarter-century ago. Now consider “pingpong journalism,” as defined by a practitioner I met earlier this month in Shanghai.

“You know how the best shots in pingpong are those that barely graze the edge of the table,” he said. “Well, we are playing pingpong journalism, just trying to touch the limits of what is allowed.” Sometimes, newspapers or television stations in this authoritarian nation go too far and are suspended or shut down. In extreme cases, journalists are still jailed. But gradually the controls are being moved back — as opponents in pingpong have to retreat from the table when faced by players who repeatedly skim shots off the very edge.

That metaphor captures one insight gained in lengthy visits to the journalism schools of Fudan University in Shanghai and Wuhan University, and conversations with working journalists, government and Communist Party officials in five cities including this national capital.

Three weeks in a nation of this size and complexity provide far more questions than answers. But if I had to summarize the impressions left with this reporter, two are uppermost. The first is the seemingly inexorable force of the movements in economic, social, business and professional life that are gradually expanding the realm of freedom in China. And the second is the strain this is placing on the society, on families and individuals and on the political structure — and the remarkable fragility of this still unfolding experiment.

To start with journalism — a kind of “canary in the mines” for measuring liberty in any society — the limits on expression are certainly being lifted. One editor explained it this way: “Our relationship to the government has not changed. Newspapers remain state-owned, in whole or in part. Editors are still disciplined by party officials. But our relationship to our readers has changed. In the past, our task was simply to mobilize the masses for whatever project or doctrine the party selected. Now, even state-owned enterprises are expected to make profits, so we must listen to our readers and respond to their interests. They do not want propaganda. So we give them real news about things that affect their lives.” In practice, that competition brings newspaper coverage of not only sports and entertainment, but also of corruption in local government, pollution, traffic problems — all the things that plague this burgeoning economy.

What is true of the working journalists is even truer of the journalism students who will be the next generation of editors and reporters. In seminars at both universities, I found them idealistic, well-informed and unintimidated. I asked one young woman, “What is important to a journalist, do you think?” She paused, then replied, “It is important to respect your readers and their needs. And it is important not to be afraid to ask questions of even important officials.”

They are learning the trade from professors who have lived and worked in the West. And most important of all, these students live on the Internet — the most open forum for ideas in China, full of Web sites that pop up in such profusion that the government cannot effectively control them.

The working journalists are part of an emerging urban middle class that those who have watched China’s changes over decades almost universally regard as the best hope for democracy in this country. A former American ambassador to Beijing, asked what the United States can do to promote democracy in China, said unhesitatingly, “Continue to invest here. Bring more economic opportunity for these talented young people to employ their skills.”

Some, he said, will be made complacent by their new prosperity and accept the constraints of living in a one-party state. But the longer their economic independence continues, the more likely they are to want to expand that autonomy to their whole lives. China, he said, is no longer a totalitarian state — one where every aspect of life was monitored and controlled by party appparatchiks. “The transition that has occurred from totalitarian to authoritarian — where individuals can make more choices for themselves but no organization is allowed to question the rule of the Communist Party — may be more difficult for China,” he suggested, “than the transition to democracy.”

Many of the small-d democrats I met dispute that last statement, and point to the ferocity with which authorities seek to eradicate any group that could conceivably challenge the monopoly of the Communist Party.

That is why China’s experiment is as fragile as it is heady.