There is something remarkably powerful about listening. Those who know Melinda Gates well—and even some of those who have met her just once—remark at how good she is at this skill. Geeta Rao Gupta, a former staffer for the Bill & Melinda Gates Foundation, who is now at the United Nations Foundation, vividly remembers the first time she met with Gates in her office, way back in 2010: “She was literally leaning in, listening very attentively, not interrupting, but acknowledging that she had heard. You know how sometimes people just have a blank face and you don’t know whether you’re being heard?” It was wholly different with Melinda, Rao Gupta says. “She acknowledges, she nods, she listens—and without interrupting, she asks really astute questions.”
I thought about that description a lot as I was reporting my feature story on Melinda and Bill Gates for our annual World’s Greatest Leaders list (please see page 44). Listening, after all, may be one of the most underrated and least acknowledged leadership skills. A few other qualities that sources used frequently to describe the Gateses might join that list as well: data-centrism, the ability to forge lasting partnerships, and one notion that came up more than any other—optimism.
“Bill and Melinda have always insisted on being optimistic,” says Helle Thorning-Schmidt, a former Prime Minister of Denmark who is now CEO of Save the Children International. “And that language of optimism, I think, has been extremely important because it also shows that if you do something, you can change the course of the world.”
Kathy Calvin, CEO of the United Nations Foundation, brands the Gateses’ variety: “unabashed optimism.” It’s a “kind of relentless optimism,” she adds admiringly.
You’ll find that same driving, upbeat sentiment in Geoff Colvin’s marvelous introduction to this year’s list (see page 54), though he calls it by a different name: hardiness. As Geoff writes: “Hardy individuals don’t see the world as threatening or see themselves as powerless against large events; on the contrary, they think change is normal, the world is fascinating, they can influence events, and it’s all an opportunity for personal growth.”
It should go without saying that such hardy-souled stock tend to make the people they lead hardier, too. Consider Los Angeles Rams coach Sean McVay, who turned his underdogs into Super Bowl contenders—and University of Virginia basketball coach Tony Bennett, who rebounded from a mighty NCAA loss last year to reel in a big win in March Madness.
Hardiness, as our cover profile suggests, also means moving fast to help others, without waiting for permission: Consider José Andrés, who gets to disaster zones with his World Central Kitchen team, sometimes before the NGOs are even set up. They’ve served nearly 4 million meals in Puerto Rico since Hurricane Maria. “We don’t sit waiting for someone to tell us what to do,” he shares with Beth Kowitt (page 58).
Kapil Mohabir, meanwhile, is helping small farmers in Guyana band together to make a living wage. And Ellen Agler is seizing the initiative to coordinate people’s work on neglected tropical diseases.
But don’t stop there. You can get the full master class by reading entries one through 50 on the list.
A version of this article appears in the May 2019 issue of Fortune with the headline “Hope and Courage Move the World.”