Richard Stengel, the State Department’s undersecretary for public diplomacy, bluntly states the problem that has been worrying him, and should worry us all: “In a global information war, how does the truth win?”

The very idea that the truth won’t be triumphant would, until recently, have been heresy to Stengel, a former managing editor of Time magazine. But in the nearly three years since he joined the State Department, Stengel has seen the rise of what he calls a “post-truth” world, where the facts are sometimes overwhelmed by propaganda from Russia and the Islamic State.

“We like to think that truth has to battle itself out in the marketplace of ideas. Well, it may be losing in that marketplace today,” Stengel warned in an interview. “Simply having fact-based messaging is not sufficient to win the information war.”

Stengel poses an urgent question for journalists, technologists and, more broadly, for everyone living in free societies or aspiring to do so. How do we protect the essential resource of democracy -- the truth -- from the toxin of lies that surrounds it? It’s like a virus or food poison. It needs to be controlled. But how?

Stengel argues that the US government should sometimes protect citizens by exposing “weaponized information, false information” that is polluting the ecosystem. But ultimately, the defense of truth must be independent of a government that many people mistrust. “There are inherent dangers in having the government be the verifier of last resort,” he argues.

Our conversation took place in Stengel’s office, the same room that was used by Secretary of State George C. Marshall, a paradigmatic figure in the American age of reason. As Stengel observed, the problems of today’s information-saturated society would have been unimaginable for Marshall, who lived at a time when information was scarce and precious, and openness brought change.

Now, says Stengel, social media gives everyone the opportunity to construct their own narrative of reality. He recalls the early days of the Islamic State in 2014, when extremists used brutal imagery to terrorize people and recruit followers. The State Department’s early counter-radicalization efforts mistakenly were “tit for tat,” arguing with jihadists’ interpretation of Islam. A better strategy, US officials learned, was to empower others who could make the case more effectively.

“The central insight was that we’re not the best messenger for our message,” Stengel explains, “because in the post-truth world, the people we’re trying to reach automatically question anything from the US government.” As the Islamic State has weakened, so, too, has its media campaign. Messages have dwindled; recruits have disappeared; the “brand” has been devalued.

Russia’s propaganda campaigns since the 2014 invasion of the Crimea have been much subtler and harder to combat. That’s partly because Moscow’s goal isn’t to confront the West head-on, but to spread doubt and mistrust within. Stengel quotes Peter Pomerantsev, the author of “Nothing is True and Everything is Possible: The Surreal Heart of the New Russia.” For a Russian leadership schooled on KGB tactics, Pomerantsev argues, “It’s not an information war. It‘s a war on information.”

Stengel dissects the pastiche of fact and fantasy on Russian media outlets such as “Russia Today” and “Sputnik” this way: “They’re not trying to say that their version of events is the true one. They’re saying: ‘Everybody’s lying! Nobody’s telling you the truth!’”

Russia’s hacking during the US presidential election had this aim of polluting the public information stream. “They don’t have a candidate, per se. But they want to undermine faith in democracy, faith in the West.” In the cyber-propagandists’ atomized, construct-your-own-narrative world, agreement on a common framework of factual evidence can become almost impossible.

How should citizens who want a fact-based world combat this assault on truth? Stengel has approved State Department programs that teach investigative reporting and empower truth-tellers, but he’s right that this isn’t really a job for Uncle Sam.

The best hope may be the global companies that have created the social-media platforms. “They see this information war as an existential threat,” says Stengel. The tech companies have made a start: He says Twitter has removed more than 400,000 accounts, and YouTube daily deletes extremist videos.

The real challenge for global tech giants is to restore the currency of truth. Perhaps “machine learning” can identify falsehoods and expose every argument that uses them. Perhaps someday, a human-machine process will create what Stengel describes as a “global ombudsman for information.”

But right now, the truth is losing. And we wonder: Which side will America’s next president take in the war on information? 

By David Ignatius

David Ignatius’ email address is davidignatius@washpost.com.--Ed.

(Washington Post Writers Group)