In 1973 travellers wrote of millions of men and women dressed in uniform blue and green, of young women with short pigtails and married women with ugly bobbed haircuts. It was a conformity that visitors read according to their tastes. The "Friendship Tourist" saw it as evidence of a new society in harmony with the ambitions of its towering leader, Mao; the sceptic as a vast prison where individuality had been sacrificed to the totalitarian desires of a mad dictator. Neither vision was entirely true, though the sceptics' view was closer to reality, and even travellers on the Friendship Tours sometimes detected a sinister undertow.
The mid-Seventies saw a pause in the struggle for China's future between Mao's vision and that of his enemies in the Party, between his ideologists and the opposing pragmatists. The ideologists were in control, ruling in the name of the ailing leader, and voicing dissent was unthinkable in a nation where so many played the policeman, either out of conviction or to save themselves. But as soon as Mao died in 1976, his followers were overthrown and China's dramatic process of evolution started again.
This process had begun with the rude arrival of the Western powers in the middle of the last century, which had spelled the end of the imperial system. The West saw in China a vast market for its goods and its religion. China saw upstart barbarians who had grown unaccountably and unjustly powerful enough to humiliate "the world's greatest civilisation". The story of the last hundred years has been, in part at least, that of China's attempt to identify and adopt the power of the "barbarian" West in order to restore its own past pre-eminence.
It was easy in the Fifties, when Marc Riboud began his work in China, to exaggerate the degree to which the nation had changed under Communism. Its new leaders wanted to transform the country entirely, to erase the Confucianism that they blamed for its weakness and humiliation. They tore down the physical memorials to the glories of past dynasties - the walls of the capital and the temples built with imperial wealth. They built monuments to the new gods of industrial power and rural transformation. They declared that miracles were not only possible but a matter of everyday currency and when the miracles failed, they blamed the gods of nature. But underneath the new uniforms of Maoism an older reality persisted. The rhythm of annual festivals remained, dressed up in Communist clothes. The balladeers and travelling opera troupes still performed, telling old stories with new names. Around the new factories, the peasants bent their backs to the same tools that their ancestors had used - the hoe and the carrying pole. Even if now they worked harder for a new collective ideal and ate less well, they were familiar with the essential demands their new government made - obedience to the local officials and the prompt payment of taxes - and learnt to repeat the words their new masters taught them, mindful, as they had always been, that power dislikes contradiction.
Even the start of the Cultural Revolution in 1966 - when Mao tried to turn build a power-base among China's youth strong enough to fight off his enemies in the higher reaches of the Party - had echoes of past events. A hundred years earlier, Hong Xiuchuan, a young man from the countryside who had failed his imperial exams, took elements of Christianity and, declaring himself the brother of Christ, set out on a path of violent revolution to create the Kingdom of Heavenly Peace, a new puritan society that he and his millions of followers believed would transform China.
In the end Mao's vision foundered on a misperception of the talents and desires of his own people. "China," he once wrote, "is poor and blank." Any story he wanted, he thought, could be written on the nation. But if the Chinese people have a gift for collective action they have a greater talent for enterprise. What kept them back in the years of the socialist utopia was the well-founded fear of persecution. When Deng Xiaoping let them off the leash in the Seventies and told them it was now okay to get rich, they took to their new task with an energy that belied the years of obedience to the egalitarian ideal.
From the blue chrysalis of the Sixties and Seventies, there emerged the multi-coloured creature of the Eighties and Nineties. In the cities, men and women abandoned the uniform of collectivism and began a cult of high fashion and conspicuous consumption. Former Red Guards bought mobile phones and began to deal in information technology. Pornography, Tai-wanese pop music and Hollywood movies displaced the official propaganda of Madame Mao's model opera; Mao himself became a hybrid of a Pop Art icon and a household deity.
There are few gods left now in China save modernity. Her rulers have the authority of power, but not of ideology. In the Sixties it was as dangerous to possess an antique statuette as to read a forbidden book or hold a dissident idea. Now you may possess what you wish, but the book and the idea are still items that carry a risk. There are opportunities, but no rights; freedom to consume but not to dissent. There is licence to grow rich and to make others poor.
For now, China has found a route to economic success that allows it to heal the wounds of the last hundred years and to meet the only national goals left from the era of socialism: the restoration of the imperial boundaries of the Qing Dynasty, most potently represented by the recovery of the lost territories of Hong Kong and Taiwan. The first is imminent; to achieve the second may require the transformation of its politics.
Twenty years ago, Hong Kong would have been an indigestible economic morsel, too rich for the Chinese diet. Now, south China has been transformed into a high-rise hinterland and there is little to mark the material difference with capitalist Hong Kong. There will still be a border, a new fence erected by China to hold back those who still have a fortune to make and will want to make it in the newly recovered territory. There will be another border, too, but one that Peking is bent on erasing rather than reinforcing - that border between a place where there is freedom to consume and one where there is what China sees as an unacceptable freedom to think and speak.
China has effected an economic transformation big enough and swift enough for it to absorb Hong Kong without indigestion. Hong Kong's politics and her freedoms are fragile enough to pose little threat, and the circumstances of history have meant that China was not required to present its political credentials before she signed the contract.
But now the completion of the national myth requires the "recovery" of Taiwan, an altogether more complicated proposition. If Hong Kong was China's economic alter ego, Taiwan is its political one. Taiwan is no colonial possession to be reclaimed when its time is up, but a democratic mirror in which China can see another facet of its own identity. To possess Taiwan, China must either break that mirror or face up to the long- postponed and uncertain aspect of its own transformation - the one that the imprisoned dissident Wei Jingsheng calls the fifth modernisation - democracy.
Marc Riboud's `Forty Years of Photography in China', Barbican Art Gallery, EC1 (0171 382 7105), 19 June to 17 August. To coincide with the show, Thames & Hudson has published a book, price pounds 35, with the same title.