And so another alliance was born: unlikely, unsentimental, hard nosed, clear eyed and dead set on driving poverty into history. The rocker's job is to be raucous, grab our attention. The engineers' job is to make things work. 2005 is the year they turned the corner, when Bono charmed and bullied and morally blackmailed the leaders of the world's richest countries into forgiving $40 billion in debt owed by the poorest; now those countries can spend the money on health and schools rather than interest payments--and have no more excuses for not doing so. The Gateses, having built the world's biggest charity, with a $29 billion endowment, spent the year giving more money away faster than anyone ever has, including nearly half a billion dollars for the Grand Challenges, in which they asked the very best brains in the world how they would solve a huge problem, like inventing a vaccine that needs no needles and no refrigeration, if they had the money to do it.

It would be easy to watch the alliance in action and imagine the division of labor: head and heart, business and culture; one side brings the money, the other side the buzz. But like many great teams, this one is more than the sum of its symbols. Apart from his music stardom, Bono is a busy capitalist (he's a named partner in a $2 billion private equity firm), moves in political circles like a very charming shark, aptly named his organization DATA (debt, AIDS, trade, Africa) to capture both the breadth of his ambitions and the depth of his research. Meanwhile, you could watch Bill and Melinda coolly calculate how many lives will be saved by each billion they spend and miss how impassioned they are about the suffering they have seen. "He's changing the world twice," saysBono of Bill. "And the second act for Bill Gates may be the one that history regards more."

For being shrewd about doing good, for rewiring politics and re-engineering justice, for making mercy smarter and hope strategic and then daring the rest of us to follow, Bill and Melinda Gates and Bono are TIME's Persons of the Year.

As it happens, they have arrived at the right time, as America stirs itself awake from the dreamy indifference with which the world's poor have forever been treated. In ordinary times, we give when it's easy: a gesture, a reflex, a salve to conscience. The entreaties come on late-night TV from well-meaning but long-discarded celebrities who cuddle with big-eyed children and appeal to pity and guilt. Maybe we send off a check, hope it will help someone somewhere stay alive for another day. That is not the model for the current crusaders or the message for these extraordinary times.

This was already a year that redefined generosity. Americans gave more money to tsunami relief,more than $1.6 billion, than to any overseas mission ever before. The Hurricane Season from Hell brought another outpouring of money and time and water bottles and socks and coats and offers of refuge, some $2.7 billion so far. The public failure of government to manage disaster became the political story of the year. But the private response of individuals, from every last lemonade stand to every mitten drive, is the human story of 2005.

"Katrina created one tragedy and revealed another," Melinda Gates said in a speech after the hurricane. "We have to address the inequities that were not created by the hurricanes but exposed by them. We have to ensure that people have the opportunity to make the most of their lives." That just about captures the larger mission she and her husband have embraced. In the poorest countries, every day is as deadly as a hurricane. Malaria kills two African children a minute, round the clock. In that minute a woman dies from complications during pregnancy, nine people get infected with HIV, three people die of TB. A vast host of aid workers and agencies and national governments and international organizations have struggled for years to get ahead of the problem but often fell behind. The task was too big, too complicated. There was no one in charge, no consensus about what to do first and never enough money to do it. In Muslim parts of Ethiopia, aid workers can't talk to teenage girls about condoms to prevent AIDS; but in Tanzania they're encouraged to. How you cut an umbilical cord can determine whether a baby risks a fatal infection, but every culture has its own traditions. They cut with a coin for luck in Nepal and a stone in Bolivia, where they think if you use a razor blade the child will grow up to be a thief. There is no one solution to fit all countries, and so the model the Gates Foundation and Bono have embraced pulls in everyone, at every level. Think globally. Act carefully. Prove what works. Then use whatever levers you have to get it done.

The challenge of "stupid poverty"--the people who die for want of a $2 pill because they live on $1 a day--was enough to draw Gates away from Microsoft years before he intended to shift his focus from making money to giving it away. He and Melinda looked around and recognized a systems failure. "Those lives were being treated as if they weren't valuable," Gates told FORTUNE in 2002. "Well, when you have the resources that could make a very big impact, you can't just say to yourself, 'O.K., when I'm 60, I'll get around to that. Stand by.'"

There have always been rich and famous people who feel the call to "give back," which is where big marble buildings and opera houses come from. But Bill and Melinda didn't set out to win any prizes--or friends. "They've gone into international health," says Paul Farmer, a public-health pioneer, "and said, 'What, are you guys kidding? Is this the best you can do?'" Gates' standards are shaping the charitable marketplace as he has the software universe. "He wants to know where every penny goes," says Bono, whose DATA got off the ground with a Gates Foundation grant. "Not because those pennies mean so much to him, but because he's demanding efficiency." His rigor has been a blessing to everyone--not least of all Bono, who was at particular risk of not being taken seriously, just another guilty white guy pestering people for more money without focusing on where it goes. "When an Irish rock star starts talking about it, people go, yeah, you're paid to be indulged and have these ideas," Bono says. "But when Bill Gates says you can fix malaria in 10 years, they know he's done a few spreadsheets."

The Gates commitment acts as a catalyst. They needed the drug companies to come on board, and the major health agencies, the churches, the universities and a whole generation of politicians who were raised to believe that foreign aid was about as politically sexy as postal reform. And that is where Bono's campaign comes in. He goes to churches and talks of Christ and the lepers, citing exactly how many passages of Scripture ("2,103") deal with taking care of the poor; he sits in a corporate boardroom and talks about the role of aid in reviving the U.S. brand. He gets Pat Robertson and Susan Sarandon to do a commercial together for his ONE campaign to "Make Poverty History." Then he heads to Washington, where he stops by a meeting of House Democrats to nuzzle them about debt relief before a private lunch with President George W. Bush, whom he praises for tripling aid to Africa over the past four years. Everyone from Republican Senator Rick Santorum to Hillary Clinton used Bono's October concert as a fund raiser. "He knows how to get people to follow him," Stonesifer says. "We are probably a good complement. We're more likely to give you four facts about the disease than four ways that you can go do something about it."

Bono grasps that politicians don't much like being yelled at by activists who tell them no matter what they do, it's not enough. Bono knows it's never enough, but he also knows how to say so in a way that doesn't leave his audience feeling helpless. He invites everyone into the game, in a way that makes them think they are missing something if they hold back. "After so many years in Washington," says retired Senator Jesse Helms of North Carolina, whom Bono recruited to his cause, "I had met enough well-known people to quickly figure out who was genuine and who was there for show. I knew as soon as I met Bono that he was genuine. He has absolutely nothing to gain personally as a result of his work. In fact, he has opened himself to criticism because he has been willing to work with anyone to find help for these children who have taken his heart."

This is not about pity. It's more about passion. Pity sees suffering and wants to ease the pain; passion sees injustice and wants to settle the score. Pity implores the powerful to pay attention; passion warns them about what will happen if they don't. The risk of pity is that it kills with kindness; the promise of passion is that it builds on the hope that the poor are fully capable of helping themselves if given the chance. In 2005 the world's poor needed no more condolences; they needed people to get interested, get mad and then get to work.