IT SEEMED to Elinor Ostrom that the world contained a large body of common sense. People, left to themselves, would sort out rational ways of surviving and getting along. Although the world's arable land, forests, fresh water and fisheries were all finite, it was possible to share them without depleting them and to care for them without fighting. While others wrote gloomily of the tragedy of the commons, seeing only overfishing and overfarming in a free-for-all of greed, Mrs Ostrom, with her loud laugh and louder tops, cut a cheery and contrarian figure. Years of fieldwork, by herself and others, had shown her that humans were not trapped and helpless amid diminishing supplies. She had looked at forests in Nepal, irrigation systems in Spain, mountain villages in Switzerland and Japan, fisheries in Maine and Indonesia. She had even, as part of her PhD at the University of California, Los Angeles, studied the water wars and pumping races going on in the 1950s in her own dry backyard. All these cases had taught her that, over time, human beings tended to draw up sensible rules for the use of common-pool resources. Neighbours set boundaries and assigned shares, with each individual taking it in turn to use water, or to graze cows on a certain meadow. Common tasks, such as clearing canals or cutting timber, were done together at a certain time. Monitors watched out for rule-breakers, fining or eventually excluding them. The schemes were mutual and reciprocal, and many had worked well for centuries. Best of all, they were not imposed from above. Mrs Ostrom put no faith in governments, nor in large conservation schemes paid for with aid money and crawling with concrete-bearing engineers. "Polycentrism" was her ideal. Caring for the commons had to be a multiple task, organised from the ground up and shaped to cultural norms. It had to be discussed face to face, and based on trust. Mrs Ostrom, besides poring over satellite data and quizzing lobstermen herself, enjoyed employing game theory to try to predict the behaviour of people faced with limited resources. In her Workshop in Political Theory and Policy Analysis at the University of Indiana - set up with her husband Vincent, a political scientist, in 1973 - her students were given shares in a notional commons. When they simply discussed what they should do before they did it, their rate of return from their "investments" more than doubled. "Small is beautiful" sometimes seemed to be her creed. Her workshop looked somewhat like a large, cluttered cottage, reflecting her and Vincent's idea that science was a form of artisanship. When the vogue in America was all for consolidation of public services, she ran against it. For some years she compared police forces in the town of Speedway and the city of Indianapolis, finding that forces of 25-50 officers performed better by almost every measure than 100-strong metropolitan teams. But smaller institutions, she cautioned, might not work better in every case. As she travelled the world, giving out good and sharp advice, "No panaceas!" was her cry. Scarves for the troops Rather than littleness, collaboration was her watchword. Neighbours thrived if they worked together. The best-laid communal schemes would fall apart once people began to act only as individuals, or formed elites. Born poor herself, to a jobless film-set-maker in Los Angeles who soon left her mother alone, she despaired of people who wanted only a grand house or a fancy car. Her childhood world was coloured by digging a wartime "victory" vegetable garden, knitting scarves for the troops, buying her clothes in a charity store: mutual efforts to a mutual end. The same approach was valuable in academia, too. Her own field, institutional economics (or "the study of social dilemmas," as she thought of it), straddled political science, ecology, psychology and anthropology. She liked to learn from all of them, marching boldly across the demarcation lines to hammer out good policy, and she welcomed workshop-partners from any discipline, singing folk songs with them, too, if anyone had a guitar. They were family. Pure economists looked askance at this perky, untidy figure, especially when she became the first woman to win a shared Nobel prize for economics in 2009. She was not put out; it was the workshop's prize, anyway, she said, and the money would go for scholarships. Yet the incident shed a keen light on one particular sort of collaboration: that between men and women. Lin (as everyone called her) and Vincent, both much-honoured professors, were joint stars of their university in old age. But she had been dissuaded from studying economics at UCLA because, being a girl, she had been steered away from maths at high school; and she was dissuaded from doing political science because, being a girl, she could not hope for a good university post. As a graduate, she had been offered only secretarial jobs; and her first post at Indiana involved teaching a 7.30am class in government that no one else would take. There was, she believed, a great common fund of sense and wisdom in the world. But it had been an uphill struggle to show that it reposed in both women and men; and that humanity would do best if it could exploit it to the full.