THIS MORNING I went out and bought a shirt. There is nothing very unusual in that: across the world, perhaps 20 million people did the same. What is more remarkable is that I, like most of these 20 million, had not informed anybody in advance of what I was intending to do. Yet the shirt I bought represents a triumph of international co-operation. The cotton was grown in India, from seeds developed in the United States; the artificial fibre in the thread comes from Portugal and the material in the dyes from at least six other countries; the collar linings come from Brazil, and the machinery for the weaving, cutting, and sewing from Germany; the shirt itself was made up in Malaysia. And yet I am quite sure nobody knew that I was going to be buying a shirt of this kind today; I hardly knew it myself even the day before. Every single one of these people who has been labouring to bring my shirt to me has done so without knowing or caring anything about me. To make their task even more challenging, they have been working at the same time to make shirts for all of the other 20 million people of widely different sizes, tastes, and incomes, who decided independently of each other to buy shirts at the same time as I did.

If there were any single person in overall charge of the task of supplying shirts to the world’s population, the complexity of the challenge facing them would call to mind the predicament of a general fighting a war. One can imagine an incoming president of the United States being presented with a report entitled The World’s Need for Shirts, trembling at its contents, and immediately setting up a Presidential Task Force. The United Nations would hold conferences and there would be arguments over whether the UN or the US should take the lead. The Pope and the Archbishop of Canterbury would issue calls for everyone to pull together to ensure that the world’s needs were met, and committees of bishops and pop stars would remind us that a shirt on one’s back is a human right. The humanitarian organisation “Couturiers sans Frontières” would airlift supplies to sartorially challenged regions of the world. In the cacophony I wonder whether I would still have been able to buy my shirt.

In fact there is nobody in charge. The entire vast enterprise of supplying shirts in thousands of styles to millions of people takes place without any overall co-ordination at all. Citizens of the industrialised market economics have lost their sense of wonder at this fact. For our ancestors who wandered the plains in search of game, such a future would have seemed truly miraculous, and the possibility that it might come about without the intervention of any overall controlling intelligence would have seemed incredible.

In Eastern Europe and the countries that used to belong to the Soviet Union there has been persistent puzzlement that any society could aspire to prosperity without an overall plan. After the break-up of the Soviet Union I was in discussion with a Russian official whose job it was to direct the production of bread in St Petersburg. “Please understand that we are keen to move towards a market system,” he told me. “But we need to understand the fundamental details of how such a system works. Tell me, for example: who is in charge of the supply of bread to London?” There was nothing naive about his question, because the answer (“nobody is in charge”), when one thinks carefully about it, is astonishingly hard to believe. Only in the industrialised West have we forgotten just how strange it is.

The sheer number and variety of shirts produced in the world is an essential part of the reason why no single individual could be in charge. There are over six billion people in the world. This vast number means that the variety of needs and styles and tastes that the shirt-making industry has to cater to lies far beyond the capacity of any individual to comprehend, let alone to organise. As anyone who has worked in a large organisation knows, people who are put in charge of a complex activity that would be better left alone never do nothing; they seek to justify their existence by simplifying and restricting that activity so that it can be controlled.

Large numbers also help us to understand one of the most mysterious features of a system with no one in charge: its apparent ability to anticipate my desire when I have done nothing to communicate that desire to anyone. We may like to think of ourselves as individuals quite unlike others, but in many respects our behaviour is highly predictable. Partly this is because of our biology: we have physical needs that are by and large common to other members of our species. Social conventions also play a part. But finally it is the sheer number of us that makes our behaviour predictable, for large numbers of people tend to behave in much more regular ways than do any of the particular individuals of which such crowds are composed.

Extracted from The Company of Strangers: A Natural History of Economic Life by Paul Seabright, Princeton University Press, available at the Books First price of £15.96 (RRP £19.95) plus £2.25 p&p on 0870-160 8080 or visit www.timesonline.co.uk/booksfirstbuy