On last week's 25th anniversary of the Tiananmen Square massacre, the contrast between China's political capital, Beijing, and its banking capital, Hong Kong, was dramatic and cause for concern.

In semi-autonomous Hong Kong vast crowds gathered for a candlelight vigil in memory of the students killed by the Chinese army a quarter century ago. Some estimates placed their number at 180,000. In Beijing there was no mention of the event. Authorities reportedly took unusually repressive steps to silence any memorial activity, including spiriting away the head of an organization of mothers who lost children during the 1989 crackdown.

Tiananmen Square in Beijing was the most famous site of that crackdown, but student demands for a dialogue with the Chinese leadership and its repressive reaction, including killing demonstrators, occurred in hundreds of Chinese cities.

Ordinary human psychology suggests that the longer Chinese authorities deny the violence they unleashed on Chinese students in 1989, the harder it will be to find any reconciliation between themselves and those, like the Hong Kong demonstrators, who have kept alive demands for less repressive, more representative government.

Recent accounts from China suggest that the authorities may be girding themselves for another confrontation. Economic growth is slowing and economic dislocation is likely to accompany any needed reforms. Meanwhile, public disaffection is growing with the evident corruption of the privileged members of China's leadership circles.

Jerome Cohen of the Council on Foreign Relations, who follows Chinese legal and human rights issues, says, "The failure to develop and use institutions to give vent to the growing sophistication and demands of the increasingly educated populace will create the greatest threat."

Some China watchers draw a parallel between the leadership's fear of another Tiananmen and the government's recent belligerent talk and actions regarding China's expansive claims of territorial rights in the South China Sea.

The flag waving is popular and deflects criticism. And the leadership probably also sees a need to shake up the armed forces and make sure of their support.

China watchers say that when Chinese leader Deng Xiaoping launched an unsuccessful invasion of Vietnam in 1979, he did so partly to challenge the military and consolidate his political power in Beijing. They draw a parallel to the aggressive military steps China has taken since President Xi Jinping assumed office in 2012.

Deng was the father of China's extraordinary economic growth through the introduction of more free-market practices. But in 1989 it was he who pushed out members of the leadership who favored dialogue with the students and called in military units from the countryside to crush the protests.

Now after 25 years of growth hundreds of millions of educated Chinese have moved into the middle class and millions have become rich.

Yet a fundamental question still faces China despite its rise as an economic powerhouse:

How can a government that denies its role in crushing the 1989 student movement, and that continues to oppress any meaningful political dialogue, long retain the trust and allegiance of the world's largest population?

And that presents this persisting challenge to the United States and other major nations:

How can we most effectively encourage China to recognize not just the financial advantages of free enterprise, but the overriding benefits of human freedom?