Two American billionaires with extremely divergent worldviews are engaging in a quiet war of rhetoric about global health and development.

One is Bill Gates; the other is Donald Trump.

On Monday, Gates is scheduled to meet with the president. And ahead of that meeting, Gates has been putting out articles and letters that seem like thinly veiled arguments against Trump’s “America First” approach to foreign aid.

In a Time magazine opinion article on Friday, Gates argued for why the cuts to global health in Trump’s budget proposal last week would actually make Americans sicker and less safe.

“I understand why some Americans watch their tax dollars going overseas and wonder why we’re not spending them at home,” Gates wrote. “Here’s my answer: These projects keep Americans safe. And by promoting health, security and economic opportunity, they stabilize vulnerable parts of the world.”

Gates went on to outline how foreign aid and investments in global health help prevent epidemics like Ebola, strengthen markets, boost trading opportunities, and put poorer countries “on the path to self-sufficiency” — all developments that benefit Americans.

That op-ed came after the Bill and Melinda Gates Foundation’s annual letter in February offered what seemed like another veiled argument against Trump’s vaccine skepticism — noting that global vaccination was in fact “the best deal”:

“Vaccines are the biggest reason for the drop in childhood deaths,” Melinda Gates wrote. “They’re an incredible investment. The pentavalent vaccine, which protects against five deadly infections in a single shot, now costs under a dollar.”

Bill added: “And for every dollar spent on childhood immunizations, you get $44 in economic benefits. That includes saving the money that families lose when a child is sick and a parent can’t work.”

Gates was a little more direct in a February interview with USA Today, saying "America First" could actually threaten global security: “If you interpret America First in certain ways, it would suggest not prioritizing the stability of Africa and American leadership.”

There’s little clarity on exactly what today’s meeting is about. But Gates will probably share some of his case for optimism with the president, reminding Trump that there’s still a lot of progress happening these days.

Citing Steven Pinker’s The Better Angels of Our Nature in the annual letter, Bill Gates wrote: “It shows how violence has dropped dramatically over time. That’s startling news to people, because they tend to think things are not improving as much as they are. Actually, in significant ways, the world is a better place to live than it has ever been.”

Trump’s White House depends on Americans believing the opposite is true: that the world is sliding into dangerous chaos, and is in need of a strong leader to set things straight.

Can Gates’s optimistic worldview trump Trump’s in this context? Probably not. But at least on Monday, Gates will get to make his appeal directly to the president.