"Nothing can separate us. We are one family."
So said Chinese President Xi Jinping after becoming the first president of China to shake hands with a president of Taiwan.
The meeting between Mr Xi and Taiwan's President Ma Ying-jeou was undoubtedly historic. And yet Mr Xi's talk of "family" reminded me of the way that a Hollywood mafia don might use the term - in a manner that mixes charm with menace.
The fact is that Beijing still insists that Taiwan is a rebel province, and reserves the right to attack its family member should Taiwan ever declare independence.
The ambiguities do not end there. On one level, Mr Xi's decision to break with decades of ostracism was the act of a confident leader. Yet the Chinese President's boldness probably reflects anxiety as much as confidence. For when he looks out at China's near abroad, he confronts a sea of troubles.
The politics of Taiwan are moving against China. Beijing is also under increased pressure from the United States over its territorial ambitions in the South China Sea.
Mr Xi has troubles on dry land too. America and 11 other nations have just agreed to the Trans-Pacific Partnership, a trade agreement that excludes China, challenging its central position in the economy of the Asia-Pacific.
Meanwhile, pro-democracy protests in Hong Kong last year have left a legacy of bitterness with the mainland, raising the prospect that Beijing's "One China" policy could be challenged in Hong Kong and Taiwan simultaneously.
What is more, all this is taking place against the background of a slowing domestic economy, see-sawing stock markets and a Chinese elite that has been deeply destabilised by Mr Xi's anti-corruption campaign.
Given all these other problems, the last thing the President needs is a new Taiwan crisis.
His decision to meet Mr Ma comes two months before a presidential election in Taiwan which is likely to result in a victory for Ms Tsai Ing-wen, the leader of the independence-minded Democratic Progressive Party (DPP), a group abhorred by the Chinese government. Last Friday's handshake looks like an attempt by Mr Xi to boost Mr Ma's Kuomintang party (KMT). But the DPP is so far ahead in the polls that the gambit is likely to fail.
If the DPP wins power and is too explicit in its rejection of Beijing, Mr Xi may feel compelled to resort to more threatening language. That, in turn, would ratchet up security tension with the US at a time when there is already a mini-crisis in the South China Sea.
During the most recent Taiwan Strait crisis, from 1995 to 1996, the US sent an aircraft carrier to the region, in response to China's military intimidation of the Taiwanese.
Since then, Beijing has adopted much subtler tactics, relying on burgeoning economic and travel ties to draw the "rebel province" gradually back into its orbit. The election of a pro-independence president in Taiwan would suggest these tactics have failed.
In the past 20 years, the military balance in the Taiwan Strait has probably tilted towards Beijing, but it would be a bold Chinese president who puts this proposition to the test.
In all this jostling for influence, China's strongest card remains the power of its economy. Almost all the nations of South-east Asia do considerably more trade with China than with the US. But that makes the TPP potentially threatening to China.
Some Chinese analysts have even called the TPP "an economic Nato", since they see it as an alliance aimed explicitly at isolating China.
America says that eventual Chinese membership remains a possibility. And it is clear that many of the signatories of the TPP, including Singapore and New Zealand, would genuinely like China to join the new trade bloc. They do not like the economic or political implications of excluding Beijing.
But the two biggest signatories of the pact, the US and Japan, are more sceptical. Some of the provisions of the TPP, such as commitments on labour and environmental law, and on cyber space, might have been designed to make it hard for China to join.
Long-term exclusion from the TPP could make China less attractive as a production base, just at the time when rising costs are eroding the country's competitiveness.
Issues such as the South China Sea and the TPP - however difficult for Beijing - are, at least, largely about government policy. The questions of Hong Kong and Taiwan are more unpredictable, and therefore dangerous, because they involve something Beijing cannot control: public opinion.
In both Hong Kong and Taiwan, there is growing evidence that the young are less and less inclined to treat Beijing's edicts with respect.
Hong Kong, which is now part of China, had its "umbrella" movement last year, demanding free elections. Taiwan has the "sunflower" movement, which also rose up last year in protest over a new trade agreement with China.
These are fiercely difficult problems for Mr Xi. But they are also problems of Beijing's own making. By insisting with such ferocity on stale political formulas, such as "rebel province" and "one country, two systems", the Chinese government has boxed itself into a corner.
Meeting the president of Taiwan is a powerful symbol of flexibility. But if Mr Xi really wants to calm his sea of troubles, he needs to change the substance of Beijing's approach to Taiwan and Hong Kong.
THE FINANCIAL TIMES