Sachs is, after all, a supreme rationalist, a numbers man among bleeding hearts, an economist with a PhD from Harvard and one of the youngest professors ever to get tenure there. He now heads up his own academic mega-think tank, Columbia University’s Earth Institute. He is poverty’s chief public intellectual, the go-to guy when, say, Charlie Rose wants to get serious about the poor. He has been called “the most important economist in the world” by the New York Times Magazine. The Daily Telegraph referred to him as a dispenser of “moral medicine.”

There are doubters, though: policy critics within the “dev biz,” as some insiders call the global antipoverty development institutions. Indeed, Sachs is at the center of a great debate—actually, several linked and probably interminable and unresolvable great debates—over the eternal poverty questions: How bad are things, really? Has the half-trillion dollars funneled into Africa in the past 50 years helped, or—as Zambian economist Dambisa Moyo, among others, says—has it actually hurt?

How could it hurt? By distorting the political culture of Africa—fattening corrupt kleptocrats who have diverted untold billions away from the needy and into Swiss bank accounts and crippled their countries’ progress toward self-sufficiency. In other words, the question is whether the corrupt political culture in these poverty-stricken nations must be reformed before aid can make a difference, or whether aid and accompanying development can reform the political culture.

Certain of Sachs’ critics within the dev biz dismiss him as “one of the world’s most gifted self-publicists” flogging “superficially attractive but deeply flawed ideas,” as former World Bank official David Ellerman puts it. He says that Sachs’ prescriptions rely on top-down, neocolonial, interventionist solutions that have failed in the past.

Meanwhile, Naomi Klein, an anti­globalization writer and activist, calls Sachs “Doctor Shock.” She accuses him of having a dark past in which he prescribed not “moral medicine” but “shock therapy” economics for populations that were already too stunned to resist.

Other critics blame him and his whiz-kid colleagues—the so-called Harvard boys, including Obama’s economics guru Lawrence Summers—for missing a historic opportunity more than a decade ago in post-Soviet Russia. The disastrous attempt to turn a titanic collectivist economy into a capitalist democracy virtually overnight—an attempt that “privatized” the Russian economy into poverty, oligarchy, and gangsterism in the ’90s—gave capitalist democracy a bad name and paved the way for Putinism and renewed political and even military hostility, as evidenced by the invasion of Georgia. Will Sachs be remembered for saving the world in Africa or setting it on the path to destruction in Russia?

Sachs calls the reporting on his role in Russia “unfair” and even “ridiculous,” but no doubt he’s a global player: He’s one of the few individuals who can be both credited with a plan for global salvation and blamed for the renewed potential for global destruction.

But we like our do-gooder icons to have problematic pasts, don’t we? It allows us to fit their lives into our favorite contemporary narrative: redemption. Reputational rehab. Becoming the Sally Struthers of intellectuals has allowed Jeffrey Sachs to largely erase his identification with the Russian fiasco and become the white knight of do-gooders, or at least their Don Quixote.

Nonetheless, what Sachs is quick to call the cynicism of his critics can, at times, get under his skin. When it happens, it comes as a bit of a surprise, because on the surface he seems a mild, unassuming, just-the-facts-ma’am type, at least in the presence of a reporter. His undramatic manner is reflected in his emphatically bland garb, the Midwestern flatness of his voice, and the hairpiece-looking (but in fact real) haystack atop his head, all of which suggest not some Northeast Corridor slickster but rather a Corn Belt farm-implements salesman. But once in a while, one can hear what sounds like a combination of injury and outrage in his voice when he gets going on the topic of those who question his solutions.

“I find the level of cynicism among thinking people unacceptably high,” he told me over the phone shortly before the Tokyo trip. “What I don’t really appreciate is the complacency of thinking people—in the sense that there are a lot of very well-trained people who should know better. And if they don’t like my ideas, they should at least feel some responsibility to not just naysay but come up with other ideas. But not to accept 10 million children dying every year of extreme poverty?”