Bill Gates makes a point of talking about how optimistic he is, which can seem like madness when you look at the massive and complex problems he and wife Melinda have set out to solve. Through the work of their Gates Foundation, they want to cut carbon emissions to zero, drop childhood deaths in half from their 2015 levels (already sliced in half from 1990 levels), quadruple the access to contraception in the developing world (from 30 million today to 120 million by 2020), bring down the number of women who die in childbirth by 75% and wipe out entire diseases: TB, HIV, Guinea worm, polio, malaria. And while they’re at it, they intend to end malnutrition.

You could forgive them for tempering that optimism a bit lately. Governments at home and abroad have started looking inward, skeptical about the value of the kind of foreign aid that developing countries rely on for those health gains. In the U.S., the Trump administration has committed to cutting environmental protections, cast doubts about vaccines and reinstated Reagan-era “gag” rules that caused contraception availability in Africa to drop.

Still, Gates's world view isn’t shaken — though maybe the time frames have stretched out. “I feel certain that things will continue to improve,” he tells me. “It won't necessarily be a purely linear path.”

Gates is in town to talk about the publication of his annual letter, a yearly look at where his philanthropic dollars and brainpower is going and what issues he and Melinda want the world to pay attention to. His letter is framed as a note to Warren Buffett, his friend and fellow world’s-richest-person.

Buffett, himself, changed the path of the Gates Foundation in 2006 when he committed to giving the bulk of his estate — 10 million Class B Berkshire Hathaway shares, then worth $30.7 billion — gradually to the Foundation and joining the board. What was already the world’s largest philanthropic organization roughly doubled in size.

Last year, Bill and Melinda dedicated their letter to the need for an “energy miracle” that would keep the planet from overheating. This year their focus is on childhood deaths and, in keeping with Buffett’s investment mindset, where his money is best being leveraged, a decade after he gave the world’s largest gift.

"A lot of people feel the world is getting more fragmented, and we all can point to examples of that," the letter explains. "But if you look along a timeline, the periods of fragmentation often come when society is digesting its new diversity. The larger historical trends are toward greater inclusion and caring... Governments are prioritizing it. Citizens are supporting it. Scientists are migrating to it. Businesses are making greater commitments to the poor because that’s what it takes to bond with their customers and attract good employees." And they add: "The future will surprise the pessimists."

Here are some edited excerpts from the interview (see the full video here):

On how logistics and government relations became core to the foundation:

In the early years, we thought we would only do upstream tools inventions, come up with new vaccines and drugs, and then this delivery piece, someone else, including the governments, must be on top of that. So we wouldn't have to get super involved in it.

Now every year we realized, wow, those primary health care systems aren't working.

But our understanding of how do you help primary health care get done well, and that that was, there were huge problems there in many of these countries that we would need to get very involved in that. Every year that's grown, and now that's a huge part of our activities are in that delivery piece… We have the best supply chain experts who understand where roads work in Africa and where they don't, and how we get all that information managed. I didn't think we'd have supply chain people, or refrigerator people, but it's a requirement.

On how he’s changed his view of the role of technology in solving the world’s problems:

Some of our stuff is really a mix of high tech and low tech. For example, polio at its most basic level, it's getting out to 95% of the kids and giving them a vaccine, the Sabin vaccine, which was invented in the 1960s. You just squeeze the dropper. If you can get 95% of the kids to have three of those, you're done. So that's just kind of the logistical communication thing.

But we kept failing polio, we got the cases down from 300,000 a year, down to about 20,000 a year. Then in India and Nigeria it just wasn't coming down. So to figure out how to get the quality of those campaigns up to make sure we were really reaching all the different settlements, we had to use satellite photography and maps, and we found out a lot were being missed. Then in terms of the execution, we put in a cell phone that would take the GPS coordinates every few minutes, and then as the team would come back we would check, and did they really go everywhere?

Being out in the field and seeing what can work, even simple things, and then using that to inform what you challenge the scientists to come up with, being on both ends, we're more balanced now.

On staying optimistic:

I feel certain that things will continue to improve. It won't necessarily be a purely linear path. For example, we are quite concerned right now that in the US, being willing to take the less than 1% of the budget that goes towards foreign aid, and it's a total of $30 billion, $10 billion of which is just health. Buying HIV medicines is a huge thing, and the world's very dependent on the US generosity there. Making sure that gets preserved despite all these changes, we'll have to fight for that, to make sure that happens. It'd be a huge setback if it didn't.

I'm not saying that everything will improve every year. But the broad picture is that innovation every year does bring us new tools.

I think it is important to get this good news out to people. If people really knew the value that $10 billion of health aid the US gives. Anybody who gets a chance to go see it comes back and testifies for it. But unfortunately, that's very, very few people.

Although this annual letter is framed very appropriately as letting Warren know the overall great things that have come out of his generosity, we want to get that to a very broad audience about our causes in general. We're not asking them to give to us or anything. But as voters, people who have priorities, only if we can get millions of people to see this, then as push comes to shove, maybe the work on HIV and malaria and helping women with their health, maybe those things will be maintained.

On working with the Trump administration:

Well, we partner with the government, because the US government and our foundation are the biggest funders of research in these areas. For HIV, we're the biggest non-government funder of even the delivery stuff. So like on polio, the person who's run the [Center for Disease Control], Thomas Frieden, he's leaving now, but he's been an absolutely amazing partner.

So yes, we're very engaged with the US government. The new administration's just coming into place. I have a meeting with President Trump to talk about some of the great achievements that the US has been key to. Now that the cabinet's coming into place, over the next month, I'll get to meet Rex Tillerson, who I knew in his previous role as CEO of Exxon Mobile. I'll get to meet James Mattis as the Defense Secretary, and understand what their goals are, and make sure they understand the partnerships we've got and the impact.

The Bush administration, 2000 to 2008, is actually where the big increases took place. The budget was a little more free and President Bush saw what was going on with HIV and malaria, got the funding up quite substantially. Then that was maintained under the Obama administration.

Now we don't know yet, but in the framework of “Is it a win-win, is it a good deal?” Is it keeping Africa stable? Is it avoiding epidemics coming out of Africa? It it getting Africa to grow economically as a market opportunity for the US? Is the US being strong in Africa? I do think, even in this new framework, this work deserves some priority.

But there'll be a lot of dialog before that gets figured out.

On how AI and automation will impact the developing world:

The opportunity that China had to become the workshop of the world for lots of different things, including tech and electronics is less there today. Now Chinese wages have gone up a lot. That's great. Their economy is shifting more to services. So you see countries like Vietnam, Bangladesh, even Ethiopia to some degree, coming in and educating their workforce enough that they're capable of doing those factory-type jobs.

But in the aggregate, manufacturing jobs won't go up the way that they used to. That's great. It means all the goods and services will be cheaper and more available. But it means that the economies will shift to a services focus earlier at a lower GDP level than they did in the past. But that's all good. It's because we know how to make this stuff using less resources. So it's a problem of excess, not a shortage.

On Buffett’s involvement with the foundation

For a lot of the things, including companies like Berkshire, he gives the leaders total freedom. So though I talk on the phone with Warren about the world and politics, economics, different businesses, we're only coming together a few times a year where it's really a review of what the foundation's up to. He's showing a lot of trust.

He's super engaged in his business. Any time we want his help or advice, he's there. Melinda and he and I are the three trustees. But it's his classic hands off approach.