The idea of bringing outside ideas, technology, and money to people mired in poverty, disease, and economic stasis has been the bedrock of development work since the end of World War II. What's new in Sachs's program is the way he is putting together private, government, and corporate money to attack poverty on all fronts, simultaneously and concertedly. Pull one village up out of poverty, and then, as Sachs says all the time, you can "scale up" to more villages and, eventually, a whole country and perhaps, in time, a continent.

"The technologies to achieve the Millennium Goals are well known but have not been applied on the proper scale and have not been integrated," says John McArthur, CEO of Millennium Promise, a nonprofit that works on the Millennium Villages Project with Sachs's Earth Institute at Columbia University, in Manhattan. The initiative is a redirection of older methods used in development work. Along with the UN Development Program, the Marshall Plan, and USAID, Sachs's project is one of the broadest and most ambitious human experiments ever launched. In some places it may well be of lasting importance. In others, it could fail utterly. It's all a matter of luck, politics, and hard work. Sachs is an expert on the last.

We fly on for a bit. As we begin our descent, I can see that Timbuktu is like that little village we just passed over, but bigger. From above, it looks like a child's sand castle, all the buildings of a uniform yellow-tan color, desert-blasted at the edges. The city itself seems to decline at its periphery, to come to its knees, gradually, and then to bow down prostrate, vanishing outwards into the desert, as if it were in the process of disappearing entirely in prayer to the desert gods. And it is disappearing. As with everything built on Saharan sands, it is being eroded, sometimes by several feet a year.

At the airport, a committee of local notables has assembled to greet the economist and his entourage. Rarely has clothing shown such clear cultural disparity as does Sachs's costume, compared with the outfits of his greeters. The Harvard--educated Sachs is in regulation American preppy uniform: khakis, navy-blue blazer, white button-down shirt open at the collar, black loafers. He could be on his way to a Connecticut country club for supper.

The Malian delegation is outfitted in colorful robes, the most vivid of which—in lavender, with embroidered African patterns, its burnished threads glinting in the desert sun—belongs to the six-foot-five mayor of Toya village, who tops it all off with an enormous white Tuareg turban wrapped around his head, the loose end dangling down to his chest.

"It's a dream for us to be here in one of the great centers of civilization," Sachs tells them. "We look forward to years of cooperation here. We want you to count on us for many years to come." The mayor is accompanied by two military men in dress khakis, as well as other local dignitaries in blue and white robes, with color-coordinated fezzes on their heads. A low-level functionary wraps our heads in long sheets of homespun cotton. Sonia's turban is blue, mine is a muddy yellow, and Jeff's is olive green.