Why we don’t know more about the Uyghurs.

As they strolled down M Street after dinner at Clyde’s, a popular Georgetown restaurant, Ekpar told his sister about the people and places he was encountering as part of his three-week program and how it was giving him confidence about China’s own future. “Look at me,” Rayhan recalls him saying. “I am in Washington, representing China as a Uyghur. China wants us to be innovative and creative.” Before he flew back to China, they met again over pizza in Manhattan. Ekpar told his sister he and their parents would come to Cambridge in May to attend her law school graduation.

The family reunion did not happen. Three weeks after returning from the United States, Ekpar was suddenly taken away by Chinese Communist authorities.

When a young Southern Baptist pastor named Alan Cross arrived in Montgomery, Ala., in January 2000, he knew it was where the Rev. Martin Luther King, Jr. had his first church and where Rosa Parks helped launched the famous bus boycott, but he didn’t know some other details of the city’s role in civil rights history.

The more he learned, the more troubled he became by one event in particular: the savage attack in May 1961 on a busload of Black and white Freedom Riders who had traveled defiantly together to Montgomery in a challenge to segregation. Over the next 15 years, Cross, who is white, would regularly take people to the old Greyhound depot in Montgomery to highlight what happened that spring day.

America, unlike some countries, is not defined by a common ancestry, nor is it tied to an official faith tradition. But it does have a distinct identity and a quasi-religious foundation.

Americans are expected to hold their hands over their hearts when they recite the Pledge of Allegiance or stand for the national anthem. Young people are taught to regard the country’s founders almost as saints. The “self-evident” truths listed in the Declaration of Independence and the key provisions of the U.S. Constitution and the Bill of Rights have acquired the status of scripture in the U.S. consciousness.

U.S. presidents as far back as Harry Truman denounced entry policies based on nationality, calling them discriminatory and un-American.

President Trump’s reported suggestion that the United States needs fewer immigrants from “shithole countries” and more from those like Norway revives an argument made vigorously a century ago—though in less profane terms—only to be discredited in the decades that followed.

Social engineering through immigration policy isn’t simple—and such efforts often produce dramatic, unintended consequences.

Trump adviser Stephen Miller says the new White House plan to amend U.S. immigration law, introduced by Senators Tom Cotton and David Perdue, is “the largest proposed reform to our immigration policy in half a century.”

The White House wants to revisit the 1965 Immigration Act, which opened America’s doors wide to immigrants of color and produced the most sweeping demographic transformation of the country in its history.

Critics of the proposal see it as a thinly veiled effort to constrict the flow of nonwhite groups to the United States. The alt-right leader Richard Spencer, welcoming such a development, told HuffPost the bill “sounds awesome.”

The bill’s proposed changes are certainly significant, but their consequences may not be easily predicted. The key lesson of the 1965 reforms is that social engineering through the adjustment of immigration policy is no simple matter—and almost any such effort will produce dramatic, unintended consequences.