You want a world-class conversation about the future of global health, the vanguard of philanthropy, and the divide between ignorance and data-driven knowledge? Bring in the Bills. Gates and Clinton, that is.

They share much more than a first name. Both pivoted from spectacular first acts to second careers devoted to tackling some of the biggest problems on the planet. To do this, they have capitalized on their previous roles, their connections, and their brainpower. In Clinton's case, it turned out that the attributes that make for the ultimate politician work equally well in the service of philanthropy.

As founder of the Bill, Hillary & Chelsea Clinton Foundation, the former president is a forceful explainer in chief, elucidating what needs to be done to alleviate poverty and treat AIDS. And to the surprise of many who followed Gates as a full-tilt techie devoted to preserving Microsoft's dominance, he has pursued philanthropy with the same passion he once channeled into software. At the Bill & Melinda Gates Foundation, he approaches problem-solving—particularly the scientific arcana of health and agriculture—with an appreciation of scale honed by years of living under Moore's law.

Both organizations have made a staggering impact. The Clinton Global Initiative, part of the former president's foundation, claims to have improved the lives of more than 430 million people in 180 countries. The Bill & Melinda Gates Foundation has by some estimates saved some 6 million lives and delivered a higher-quality existence to many, many more.

The foundations are at the forefront of a new era in philanthropy, in which decisions—often referred to as investments—are made with the strategic precision demanded of business and government, then painstakingly tracked to gauge their success. The Gates Foundation shot to philanthropic heights instantly after its launch in 2000, with the world's richest man pledging the bulk of his fortune—$28.7 billion so far—and, after 2008, the bulk of his attention. (Gates has challenged other rich industrialists to follow his altruistic lead, most notably his pal Warren Buffet.) Making use of a mind so precise and logical that it once crunched the entire Basic computer language into 4 kilobytes of memory, Gates demands metrics to show that his investments are getting results. "I have been struck again and again by how important measurement is to improving the human condition," he wrote in this year's annual progress report. One current priority: Gates is pursuing the world's remaining cases of polio with the zeal of a Javert. His foundation's activities include expanding the role of libraries as digital centers, revamping teacher evaluations, promoting genetically redesigned seeds, and devising improved condoms and toilets.

The Clinton Foundation is less a funder than a launching pad for projects benefiting the global good. It organizes its interests in nine separate tracks, encompassing achievable goals that range from improving AIDS treatment to reducing greenhouse gas emissions. These are often in sync with the United Nations' Millennium Development Goals, benchmarks to improve conditions in eight key areas, including combatting poverty and disease. The Clinton Global Initiative encourages its deep-pocketed members to take action, requiring them to make commitments once they figure out what projects to undertake. Each commitment must be original, specific, and measurable. CGI facilitates the projects, often by tapping its extensive networks.

Gates and Clinton have long bonded over their shared mission. They have traveled together to neglected corners of the world—fodder for a buddy movie that Hollywood has so far missed. "I knew him before he was president, I knew him when he was president, and I know him now that he's not president," Gates remarks with a smile while waiting for his friend to arrive. He talks fondly of their forays into developing regions and cites the close partnership between their organizations. (Not mentioned: whether, on some long bus ride to a South African village, Gates asked his traveling partner about that antitrust thing that Clinton's Justice Department waged against him.)

This interview took place on September 23 at the annual Clinton Global Initiative meeting, a kind of wonk Woodstock occurring in conjunction with the opening of the 67th session of the UN General Assembly in New York. The 42nd president was ubiquitous at his event, moderating a panel that included Bono, Sheryl Sandberg, and Christine Lagarde. Gates himself bounced between the conference and the UN, appearing on a CGI panel (“‘Big Bets’ Philanthropy") and meeting with the leaders of Chad, Ethiopia, Pakistan, Japan, and Canada. After warmly greeting each other, the two Bills jumped into conversation, edited here for space and clarity.

Both of you are embarked on your next careers, helping to change the world. How do you decide what to focus on?

Clinton: When I left the White House, I decided to focus on things that I had cared about when I was there, where I could still make a difference. One is our Health Access Initiative, thanks largely to funding from the Gates Foundation. Building health systems is important. We've been able to drive down the price of AIDS and malaria drugs, and we're now distributing millions of [antidiarrheal] oral rehydration therapy and zinc packages a year. Another is the Clinton Global Initiative, where I try to build a global network of people to do their own thing. And then we have a huge effort against childhood obesity in America. We got the soft drink and juice companies to agree to reduce by 90 percent the total calories in the drinks they ship to schools.

Gates: Melinda and I always knew we'd have the responsibility and the enjoyment of giving resources away, and so it was an exploration process, traveling throughout the world. When we saw the poorest, it became the thing to go after. It's been exciting that the kind of work I've done at Microsoft—backing scientists and seeing how work can actually get delivered—is pretty similar.

You and President Clinton have traveled together. How does a famous pair like you escape the celebrity bubble to connect with the people you want to help?

Clinton: We go to a lot of places where people have no television, so we're not all that famous. You just have to go to these places and ask questions. When Bill and I went to Africa [in 2006], Melinda was with us, and she asked better questions than we did on some of these HIV/AIDS prevention efforts.

I understand that one situation put you face-to-face with an African couple to discuss their use of a microbicide to protect the woman from getting HIV.

Gates: We were trying to understand what the experience was like for her and her partner—but neither Bill nor I were willing to ask that in a very direct way. We were sort of hinting at it. But Melinda was able to ask both the man and the woman very directly. This was in South Africa, and then we went to Lesotho. Nobody knew us there. You know, if you want to get away from that kind of [celebrity] craziness, working in Africa is great for it.

Clinton: All they knew was that we were showing up trying to help them. I was just in Malawi at one of our farm projects, and the woman that we were helping there had been farming an acre with a hoe, and she had learned new planting techniques. She looked at me and said, "You think you could do this? Well, do it, then." And I got a hoe and we were planting together. She said, "How'd you learn to do this?" And I explained that when I was 6, I lived on a little farm like this. Helping them live their lives is much more important than who we used to be. Do you agree with that?

Gates: Sure.

Nadav Kander

Both of you contend that spending on infrastructure and basic research is really important, yet we're not investing at the pace we should. And while scientists agree that global warming is real, a lot of people doubt it, and we're not making as much progress on that as we should. How do we as a society deal with denial? How can we make decisions based on fact rather than fiction or fantasy?

Gates: In terms of funding science, both of us agree that we need to do more. The budget growth for the National Institutes of Health during President Clinton's time was fantastic—I think it doubled. Now the question is whether it will level off or even perhaps go down. The US should do more, but relative to others we've done more in the basic sciences, and the world has been a huge beneficiary. The US pays more for drugs, and therefore funds more R&D, than any other country. Hopefully there will be more understanding of science as the world gets richer and more people are educated. So despite some things we all think shouldn't be controversial—like GMO foods or climate change—I think the trend is in the right direction. Awareness and understanding will increase.

Clinton: I was lucky, because when Newt Gingrich was Speaker of the House, he and I fought over everything except science. We spent a half billion dollars on nanotechnology research. In this current budget climate, they need to work out some bipartisan deal to keep our future in good shape. That's the one thing I'm really worried about long-term. As far as climate change, it's still a big battle in America, but I think the key there is to prove that it's good economics to reduce greenhouse gas emissions.

No one in the US wants anything like the political system in China, but sometimes I hear people wistfully compare our situation to one in which a totally empowered engineer like President Xi Jinping can make a huge difference. Meanwhile, by some metrics, the United States is losing ground as a global technology leader. Is the era of American exceptionalism coming to an end?

Gates: Nation-state competition is not zero-sum competition. It was not good for the world for the United States to be so far ahead, for 5 percent of the global population to generate 30 percent of the economic activity and 60 percent of the scientific R&D. The way China runs its economy today is far better than it was, and we're all better for it. It's OK for China to invent cancer drugs that cure patients in the United States. We want them to catch up. But as the leader, we want to keep setting a very, very high standard. We don't want them to catch up because we're slowing down or, even worse, going into reverse.

Clinton: I agree. We should never want to hold anybody else back. America needs to stop majoring in the minors. That is, we need to look more at what other countries are now doing better than we are and learn from it instead of being in denial about it. We have laboratories of innovation all over the world: How much do we spend on health care compared to what the two highest-rated systems—Germany and France—spend? What are the Chinese really good at? Answer: aggregating capital and investing in technology and infrastructure. What's their weakness? They tend to see a big engineering solution for every problem, so in trying to run water from the Yangtze River down to the Yellow River, they may dry them both up. What are the Indians really good at? They're good at technology and entrepreneurialism, but not good at aggregating capital. Is there a way we can help each do the other? We need to be working on these things together. Nobody's got an interest in massive drought. If you believe we're living in an interdependent world, then we should be trying to build a future of shared success and responsibility.

In a recent interview, Bill Gates mocked Google's attempt to use balloons that deliver the Internet to connect the two-thirds of the world still without it. On the other hand, some innovators are on a crusade to provide universal connectivity. What is the value of connecting all the world, and is it worth the effort?

Clinton: Connectivity can be incredibly empowering to people at the bottom of the economic pyramid. When the tsunami hit South Asia, along with new boats we gave all the fishing families a cell phone. Once people could know what the price of fish was 30 miles down the way, the average income went up 30 percent. After the Haiti earthquake, we realized that 85 percent or more of the people had no access to banking services. The six big banks there made easy money by just charging a fee to convert all the remittances from Haitians working around the world into local currency. Then the bankers could spend the rest of the day reading the newspaper. So we got a Canadian bank to partner with the biggest cell phone company to offer basic consumer banking services over the Internet. If you don't have connectivity, you can't do that stuff.

Gates: Connectivity is an amazing thing, like connecting up a health center so we can get advice to a health worker who may not be trained as a doctor. And getting connectivity to schoolrooms is a fantastic thing. Connectivity enables transparency for better government, education, and health. It's one of the many things that will help us do a better job. But there are other important things—government, measles vaccines. We have to prioritize those things.

When it comes to privacy, connectivity is another matter. Microsoft, with Bill Gates at the helm, fought to build encryption into the company's products—technology that would protect customers' information. The Clinton administration, meanwhile, tried to reconcile the spread of cryptography with national security. We seemed to have reached a balance, but the Snowden leaks revealed that data collection by the NSA was far more widespread than assumed. What is the proper balance of surveillance and security, and where do we go from here?

Gates: Historically, privacy was almost implicit, because it was hard to find and gather information. But in the digital world, whether it's digital cameras or satellites or just what you click on, we need to have more explicit rules—not just for governments but for private companies. There are legitimate reasons for the government to watch what's going on, particularly with nuclear and biological weapons. So it'd be nice if there was a way that some part of the government that we really trusted was looking at that information. Right now, people are going, "Oh my gosh!" and you wonder—did they not think anything was going on? But it's probably good there is now an explicit conversation.

Clinton: In a funny way, while our handling of Big Data has made the erosion of personal liberty more likely, it has also made more likely the loss of legitimate national security secrets. I started calling around to friends of mine who are in this business, and they believe there are technological fixes to protect national security secrets. Why do 5 million people have security clearances? And why are they able to go all across an information landscape instead of being more tightly siloed? And why was the Foreign Intelligence Surveillance Court unable to pick up when the National Security Agency gathered more data than they approved? Did the NSA make an honest mistake? It appears that maybe they did. But we need to be transparent about the issues. We all need to be non-Luddite civil libertarians, a phrase that a friend of mine coined. If there are terrorist groups operating in America and we can tell by patterns of calls made or emails sent, I'd like for somebody who's trying to protect our future to know that. I'd also like to know with greater certainty than I now do that the ordinary telephone calls and other communications of citizens can't be penetrated. This is more or less a permanent challenge, and I think it's a little out of balance now on both sides.

Our guest editor Bill Gates has a question for President Clinton.

Gates: With all the distractions, domestic disagreements, and crises in places like Syria, how do we keep the basics of childhood and maternal survival on the agenda? There are so many other things that always take our attention and resources elsewhere.

Clinton: I guess the short answer is, I'm not sure we can. I would like to see the United States continue to do more in this space, because we're not quite on track to meet the United Nations Millennium Development Goals. But there has been nearly a 50 percent reduction in mortality among children under 5. That's a huge deal. I think what we need to show people is that if we invest money wisely, we can actually save a lot of aid money and it won't cost as much as you think. We could argue that this is good economics, that conservative Republicans should support it just like liberal Democrats, because nobody wants a baby to die. Washington should just keep looking for issues like this. They're bound to find some things they agree on, and it gets to be a habit. Once you establish trust on two or three things, no matter how small they may seem, you can make good things happen.

Clearly, both of you are optimists. In the past few years, when it's been tough politically and economically, has that optimism been challenged?

Gates: If you spend too many days in Washington, DC, you can have brief moments where you wonder if this system that's worked so well for hundreds of years somehow has hit a rut. But in general, I'm very optimistic. We've got innovation—whether it's new vaccines, new seeds, new ways of delivering things, connectivity. Even in education. We've got people in Rwanda trying out MOOCs [massive open online courses]. The pace of innovation is faster today than ever. You can be impatient about getting it out there, but nothing's really taken away my optimism.

Clinton: Unless some extra-system threat like global warming turns out to be worse than we thought, or there is a breakdown in our defenses against biological and chemical weapons, we're going to be OK. The whole history of humanity is just one long battle between conflict and cooperation and between us and them. Bill Gates made the money that enabled him to do this magnificent work today, because we kept expanding the definition of us, whoever the us was, and shrinking the definition of them. Yeah, this is tough, and there are a lot of complex psychological identity questions in American politics today, aggravated by this long-stagnant economy for most people. But we've had a lot of periods of bitter conflict. We're going to get through it. The trajectory is still good."