But we live in a small world, that of disillusioned western societies with media busy supplying bad news. The disappointments that that arouses distort historical perspective. The 20th century has spread as never before the idea that human happiness is realisable on Earth. Even the poorest can now glimpse the possibility of change in their lives for the better. They are no longer trapped by the conviction of millennia that things will always be the same.
More important still, millions of them have come to believe that beneficient change can be sought, promoted and actually brought about, and even that it ought to be. Politicians build careers telling them so. This has never happened worldwide before. But we all seem to behave as if more of our problems are in principle remediable or soluble than our parents and grandparents thought: that fact embarrasses the NHS as much as it does governments in developing countries which cannot even deliver public order. It is a revolution in human attitudes.
The ultimate roots of such a change, potentially the most fundamental and far-reaching of an era of unprecedented change, of course lie deep in the past. The notion that human destiny is in principle manageable could be traced back to pre-human beings learning to use fire or put an edge on a piece of flint. The abstract idea that such manipulation of the world by mankind could be indefinitely extended, globally though, took shape only much more recently, and in a few crucial places, above all in developed societies. It has become a commonplace only in the last few decades. But it is now taken for granted that people everywhere should and will begin to ask themselves why things should remain as they are when they could evidently be made better.
Material betterment is one great carrier of such change. It is most crudely expressed in a quadrupling of humanity in a century: that implies at the very least a vast increase in wealth in the most obvious form, food. People still starve, but thousands of millions now live much longer than their forbears did a hundred years ago.
Of course, the costs of any sort of change, like its benefits, now global, rarely please the fastidious or fearful. In Delhi and Jakarta, Sao Paulo and Paris alike, the internal combustion engine imposes its brutal demands. Satellite-dish receivers for programmes made for international transmission sprout like fungi on walls and roofs everywhere. But they spread similar images of better lives, whatever the material realities of the slums of Nairobi, Cairo, Calcutta and Mexico City.
Harsh as life still can be, the old iron rhythms of peasant life are everywhere slowly in retreat and perhaps for the first time in millennia a majority of people in the world does not get its living directly from the land.
But we are dismayed to discover places where the 20th century still seems yet to arrive. The last 10 years have displayed in Balkan Europe the full repertoire of medieval barbarity; yet those who launch pogroms, who murder and gang-rape their ethnically different neighbours wear the same clothes and use the cant of nationalism and democracy much as other Europeans do. They are victims and agents of the unchanging, of the inertia of history. The Ottoman Empire has long gone, but those who dispute the spoils of the Ottoman Succession go marching on in the new Balkan wars and in the struggles of the Near and Middle East.
In 1901, many people could feel confident that new and dynamic changes would come from science, liberalism, enlightenment. Few of their guesses were right, and now guesses are harder still. We can hardly say, as so many did a hundred years ago, that the future ahead will come so decisively and overwhelmingly from European or "western" civilisation, as it did for three or four centuries. But one sign of that immense shaping cultural power had been the world's adoption of a chronology based on the Christian calendar, which should remind us that millennial dates are conventional and merely historical creations, too.
The century which will begin on 1 January 2001 will have still more history to look back upon. But the history men write - even that of this century - will never be fixed. Human nature will always find new reasons to look at its past and ways to see it. We should not predict - and certainly not talk about any end to history.
Professor JM Roberts latest book, `Twentieth Century - A History of the World - 1901 to the Present' is published by Allen Lane (pounds 20)Reuse content