Francis identified social networks as the delivery systems for such fake news.

“Untrue stories can spread so quickly that even authoritative denials fail to contain the damage,” he wrote, adding that those living virtual lives in like-minded silos allow disinformation to thrive and that the absence of opposing viewpoints turns people into “unwilling accomplices in spreading biased and baseless ideas.”

Russian hackers took advantage of just such conditions in the 2016 American elections, sowing discord and attempting to sway the electorate through sophisticated influence campaigns. Francis steered clear of such real-world examples. Instead, he broadly identified greed as a key engine for the spread of fake news.

“Fake news often goes viral, spreading so fast that it is hard to stop, not because of the sense of sharing that inspires the social media, but because it appeals to the insatiable greed so easily aroused in human beings,” he wrote.

The results, he said, are soul-killing.

Turning to the “The Brothers Karamazov,” he quoted Dostoyevsky: “People who lie to themselves and listen to their own lie come to such a pass that they cannot distinguish the truth within them, or around them, and so lose all respect for themselves and for others.” This leads to the coarsening of society, Francis said.

To combat fake news, the pope called for personal efforts to unmask disinformation, but he also praised educational programs, regulatory efforts and social media companies’ progress in verifying personal identities “concealed behind millions of digital profiles.”

In recent years, the European Union and several European countries have established offices to combat fake news — this week, Britain became the latest. And fake news has emerged as a major theme in the Italian elections scheduled for March 4, and it is often discussed in the Italian news media that imbues the Vatican.

The speaker of the lower house of the Italian Parliament, Laura Boldrini, has backed a program in Italian public schools to teach children how to identify fake news. The government announced this month an online service through the country’s postal police that would respond to, and assess, accusations of fake news.