I belong to a fortunate generation. Born in the United Kingdom in 1944, toward the end of a world war that killed between 70 million and 85 million people, I have neither been bombed nor had to fight on any battlefields.

I grew up in a country and continent that were at peace and thus able to enjoy the economic benefits of unprecedented cross-border cooperation. The West repelled the Soviet Union’s military threat without conflict, thereby liberating its European empire to join the rest of a free continent.

In particular, Europe and other parts of the world benefitted from the leadership of the economically and militarily powerful United States. More important than America’s hard power was the power of the ideas that it embraced, exemplified, and exported. The US was far from perfect, and it made mistakes. But overall, it set a prodigious example of generosity and demonstrated the boundless possibilities of well-ordered freedom.

The US system was pluralistic, democratic, and bound by law. As Alexis de Tocqueville had observed in the 1830s in his great book Democracy in America, the popular will was constrained by constitutional checks and by public behaviour and attitudes. The system was democratic, but liberal in the sense that it safeguarded individual and minority opinions and interests (with the admittedly significant constraint of white supremacy).

Others followed suit. Britain liked to give the impression that liberal democracy was its own invention, and its greatest export. Even Karl Marx quietly admired Britain’s parliamentary accountability, independent courts, and strong executive.

For more than a half-century after World War II, liberal democracy was on the march. The Soviet Union’s brand of communism retreated and eventually collapsed, and dictators almost everywhere were threatened by the idea of freedom.

But one huge tyranny thrived and prospered. Following the Soviet Union’s collapse, China, ruled by its own communist regime, resumed the economic status that came with being the world’s most populous country, and took advantage of the open markets secured by the world’s liberal democracies, with their belief in a cooperative international order.

As a young politician, I took the theories about good governance in open societies largely for granted. But when I served as governor of Hong Kong in the 1990s, I saw the benefits that flow from the rule of law, independent courts, freedom of speech, an open economy, and political pluralism in a new light. Governing a city largely inhabited by refugees from a communist dictatorship was a full-on tutorial in all those values that I had long assumed but not really thought through.

Now those values are being stripped from Hong Kong, as the Communist Party of China brazenly and enthusiastically begins to destroy it as a free and open society. The CPC’s assault on Hong Kong’s autonomy is not surprising, because the territory represents precisely those values that China’s leaders regard as a threat to their rule.

Chinese President Xi Jinping and his cronies feared that globalisation, urbanisation, and the internet might endanger their dictatorship. So, they cracked down on dissent, repressed civil society, pursued a policy toward Muslim Uighurs in Xinjiang that amounts to genocide under the United Nations definition, and took aim at all those elements of liberal democracy they regard as incompatible with CPC rule.

Conveniently for those of us outside China, Xi listed these liberal democratic threats in the instructions he issued to party and government officials in 2013, soon after becoming president. They include ‘Western constitutional democracy’, the promotion of universal rules of human rights, media independence, civic participation, and criticism of the CPC’s past. Taken together, they amount to a pretty good description of the values that Hong Kong represented and which Xi’s regime now wants to obliterate.

Standing up to such assaults on liberal democratic values requires a robust response to hostile behaviour. Above all, liberal democracy’s defenders must show that they themselves still believe these values are worth fighting for.

The UK under Prime Minister Boris Johnson is not setting a good example. As incompetent governance takes its toll and the consequences of mendacious populism snowball, there are worrying signs of corners being cut in our political system—for example, a blurring of the boundaries between private and party financial interest and ministerial responsibility.

The UK has no codified constitution, but we had always assumed in the past that the ‘good guys’—irrespective of the party—would know how to behave when in power. The good guys seem thin on the ground just now.

Likewise, the European Union is a community of values as much as an economic and trade bloc. But the behaviour of member states such as Poland and Hungary has called into question their commitment to liberal democracy.

Above all, in the US, President Donald Trump is widely criticised, even by lifelong Republicans, for not respecting or understanding the US constitution and the separation of the executive, legislative, and judicial branches. Does Trump even believe in democracy? Does he want all Americans to vote in November, regardless of race or party affiliation, or only those who will support him? And will he accept the election result if it goes against him?

To save liberal democracy, it is not enough to stand up to external threats. We must also continue to practice what we preach.

—Project Syndicate