Bill Gates told Fortune that the commitment will help the foundation eradicate or dramatically reduce the world’s deadliest diseases and cut maternal and child mortality rates to a fraction of what they are. “By spending the money sooner than later, it allows us to be very ambitious,” he said. 

While “spend down” foundations are becoming more popular, the decision by the world’s largest private foundation is a marked departure from other such large organizations. The charitable endeavors of the industrialists of old, such as the Fords and Carnegies, were set up to endure for generations.  

“This is by far the most significant kind of example that we’ll have of a spend-down foundation,” Michael Moody, a professor of philanthropic studies at the Lilly Family School of Philanthropy,  says. “People will be watching this as an example.” 

The move comes at a fraught time for global public health and the charitable sector more broadly, with the Trump administration dismantling the country’s international aid infrastructure and the agency that oversees it, while also cutting domestic programs designed to help the most vulnerable.

For Wendy McGrady, Chair of Giving USA, a nonprofit organization founded by the Giving Institute to advance research, education, and public understanding of philanthropy, the news signaled that the moment we’re in calls for bold action. “Perhaps there is a line in the sand to say, let’s not do it incrementally,” she said. “Let’s go all out.” 

Una Osili, associate dean for research at the Lilly Family School of Philanthropy, agreed. When global health progress is being threatened, she said, it doesn’t make sense to save money until it’s “too late.” “The idea is, if you want that to be around for the future, you have to invest now,” she said.

“It was inspiring,” she said of Gates’ decision. “This is a bold step for the Gates Foundation and for the field.” 

Cari Tuna, chair of Open Philanthropy, who spoke at a Gates Foundation event following the announcement in New York City, said the fragility of the sector requires fast action. “The gains of the past few decades aren’t guaranteed to continue; right now, they’re at risk,” she said, “unless more of us step up and get involved.”

Alongside the optimism, however, there was some anxiety. As the Chronicle of Philanthropy put it, the decision “​​could unnerve nonprofits grappling with how to respond to the Trump administration’s near-total elimination of international aid and efforts to roll back funding for domestic causes such as higher education and affordable housing—areas the Gates Foundation has funded over the years.” And Gates himself admits that how much he can get done in the 20 years is “probably the biggest unknown,” given the pullbacks of foreign aid.