When Sachs gets up to speak ("President Jeff Sex," Toya's mayor announces), he has to explain the project to his listeners; a Malian translates the speech into Bambara, the nation's lingua franca. "I bring many partners who are interested in Toya," Sachs tells the silent crowd. "A movie star—you can see him on television, his name is Matt Damon." Around him the faces are blank. "The Secretary-General of the UN sends his good wishes." More blank faces: Damon and Ban Ki-moon, equally unknown quantities here. "And many international businesses want to help you," Sachs tells them. "A company called Sony, which makes computers, wants to give them to you." But what do they know of Sony or computers? He tells the crowd that there are "many exciting things we'll do together in the coming years." Among these he includes introducing new seed varieties, better irrigation, veterinary health care, fishing, a new ambulance, computers for the school, and even the development of tourism as a source of revenue. These are things the people understand better.

As President Sex continues, children on the sidelines sit in the sand near their mothers, and skinny-legged boys run with sticks and hoops. The sunlight plays across the lenses of Sachs's eyeglasses as he speaks from beneath the huge architecture of his turban. Jeffrey of Arabia, I think.

During lunch in the meetinghouse, the two lambs in their entirety are brought to the table on huge platters for us to deal with and dismantle. Sachs, intent on winning over the village chiefs, eats heartily. Later, village boys who had been standing outside rush in, grab the lamb bones from the tables, and pick the deserted room clean, absconding with the dregs of our sodas. Instead of their underlying despair, Sachs seems to see the exultant joy with which the boys greet the poor, unexpected treats. He is a confirmed optimist.

"I want to live here," he says after lunch, looking around the barren desert village and beaming.

Despite his passion for grassroots scenes like the one in Toya, Sachs's network is truly global—intentionally so. As he writes in his best-seller The End of Poverty: Economic Possibilities for Our Time, "The end of poverty will require a global network of cooperation among people who have never met and who do not necessarily trust each other." In the 1990s, the rock star Bono spent time at Harvard studying with Sachs, and the two have worked together on many Africa-related projects since. Sachs has served as an economic adviser to the UN under both Secretaries-General Kofi Annan and Ban Ki-moon.

Sachs's approach is based on a grand philosophical idea involving a rebalancing of global wealth. The Millennium Villages' investment generally provides about $110 per villager a year for five years. To those philanthropists who help finance the program, such a sum is unimaginably tiny, even meaningless. To the villagers, it is not only a lifeline but possibly a fortune.