Ever since the reign of the first emperor, who oversaw the burning of Confucian texts in 213 B.C., Chinese leaders have valued the science of censorship. To release a book in China today, foreign authors must accept the judgment of a publisher’s in-house censors, who identify names, terms and historical events that the party considers unflattering or a threat to political stability.

When the Chinese edition of Khaled Hosseini’s novel “The Kite Runner” was published in 2006, critical references to the Soviet occupation of Afghanistan were removed. (For Chinese authors, the stakes are incomparably larger; they either heed restrictions or lose the ability to publish in their home country. Prosecutors can cite published writing as evidence of “incitement to subvert state power.”) If publishers overlook a taboo, the State Administration of Press, Publication, Radio, Film and Television can pull books from the shelves and punish those responsible. Similar scrutiny applies to television shows, films and radio programs, and the government keeps an especially close eye on broadcasting, because it reaches the most people. When President Obama, in his first inaugural address, mentioned earlier generations who “faced down fascism and Communism,” China’s state broadcaster cut away. The word “Communism” did not appear on transcripts published in the Chinese press.

Living and writing in Beijing from 2005 to 2013, I found that the precise boundaries of the censored world were difficult to map. Though some rules leak to the public — last month, the State Council Information Office advised all websites to “find and remove the video titled ‘Actual Footage of Chengdu Police Surrounding and Beating Homeowners Who Were Defending Their Rights”’ — most of the censored world is populated by unmentionable names and untellable stories, defined by rules that are themselves secret. The Central Propaganda Department, the highest-ranking agency responsible for “thought work,” does not report on its activities; it is so averse to attention that its headquarters, on the Avenue of Eternal Peace, have no address or sign. To quantify one realm of Chinese censorship, researchers at Carnegie Mellon University, in 2012, studied messages on Sina Weibo, the social media site. They found that more than 16 percent of all posts were deleted because of the content.

One known fact about China’s censored world is that it is growing. Movie theaters are proliferating by the day, and Hollywood makes the cuts required to reach them. The makers of “Skyfall,” the latest James Bond film, removed a scene involving the killing of a Chinese security guard, and a plot line in which Javier Bardem says he became a villain during his time in Chinese custody. The New York Times has been unable to receive new residency visas for journalists for more than a year, because it reported on the family wealth of Chinese leaders. Bloomberg News is facing similar retaliation for its investigations of party officials. In March, the Bloomberg L.P. chairman, Peter T. Grauer, said the company “should have rethought” the decision to range beyond business news, because it jeopardized the company’s potential market in China.

But as I considered publishing a book in China, local publishers gradually filled in a road map of the censored world. On behalf of a company in Beijing, an agent wrote, “To allow the publication in China, the author will agree to revise nearly 1/4 of the contents.” The publisher had itemized trouble spots chapter by chapter, beginning with a line in the prologue: “China has never been more pluralistic, urban, and prosperous, yet it is the only country in the world with a winner of the Nobel Peace Prize in prison.” (The first half of the sentence could stay.)