It seems clear that Donald Trump is determined to pursue the isolationist policies he promised during the campaign. In his interview with ABC News, President Trump acknowledged that his goal was to erect barriers—both physical and psychological—for those wishing to come to the United States.

The president reaffirmed in a speech at the Department of Homeland Security that his administration would build a border wall, and that Mexico would pay for it, ultimately. (Mexican president Enrique Peña Nieto disagrees.)

If Trump succeeds in building even a portion of the border wall, it would be a tangible symbol that the president could point to, be pictured with and stand in front of to entertain the press. He could also surround himself with some of the fifteen thousand additional border-patrol and customs-and-immigration agents that will soon swell the ranks of the federal workforce.

Separately, the president last week issued an executive order that would temporarily ban all refugees coming to the United States from Syria, plus six other predominantly Muslim countries: Iran, Iraq, Libya, Somalia, Sudan and Yemen. Surveying terrorist attacks carried out on U.S. soil since 1975, my Cato Institute colleague Alex Nowrasteh concludes that zero Americans have been killed by foreigners from these seven nations. President Trump’s order curiously does not apply to several countries that have produced actual terrorists, including Saudi Arabia, Egypt, Pakistan and the UAE.

The president claimed that his actions would “save thousands and thousands of lives.”

But, of course, we won’t ever know the effect these measures will have on public safety. We can’t know how many crimes would have occurred had these policies not been implemented. The president aims to fix that as well, creating a new public-relations office to call attention to crimes committed by foreign-born persons here illegally. This will surely heighten the sense among many Americans that all foreign-born men and women pose an urgent threat.

The facts show otherwise. Based on the number of violent crimes committed by immigrants, we should expect that making it harder for people to come here will have, at best, a negligible impact on the crime rate. The terrorism danger posed by refugees, in particular, is vanishingly small: an American has a 1 in 3.64 billion chance of being killed by a refugee in any given year, according to Cato’s Nowrasteh.

But, barely a week into Donald Trump’s term as president, we have already seen that his administration struggles with the facts, or prefers certain facts that serve their policy preferences over those that do not. In that sense, the Steve Bannons of the world might argue that the mainstream media spends too much time focusing on the mass murders perpetrated by deranged, sadistic, pasty-faced, native-born men, so the Trump administration’s decision to focus on murders committed by foreigners will merely balance the scales.

That there is no compelling reason for these policies on security grounds hasn’t deterred the new administration from pursuing them. They simply want fewer people to come to the United States. In that interview with ABC News, President Trump stated, “It’s going to be very hard to come in. . . . Right now it’s very easy to come in. It’s gonna be very, very hard.”

Anyone who has encountered the current U.S. immigration system would likely quarrel with that latter “easy” claim, but we shouldn’t miss the implications of the former.

A similar mindset turned away untold numbers of Jews desperate to flee Hitler’s terror during World War II. Many Jews did come to the United States in the late nineteenth and early twentieth centuries, in part to flee anti-Semitic pogroms. One wonders if Donald Trump thinks it was a mistake to let them in.

Foreign-born scientists were instrumental in the building of the atomic bomb during World War II, and recent immigrants to the United States have developed some of America’s greatest innovations, or started our most successful companies. Trump’s message to all of these people, and millions more like them, is that they should take their talents elsewhere.

He is equally dismissive of the sacrifices of immigrants, or the children of immigrants, in our armed forces, as his shameful assault on the Khan family during the campaign revealed. (Kudos to the Department of Defense press office for sending around the story of Iraqi-born Marine Cpl. Ali J. Mohammed.)

The fear of, and intimidation toward, immigrants in the United States—especially Muslim immigrants—has been building for some time. But I worry that we are on the precipice of something much worse. We are witnessing a concerted effort by the Trump administration to distance Americans from the rest of the world, both literally and figuratively.

Ronald Reagan taught us that great countries don’t build walls; they tear them down. Trump’s isolationism won’t make us safer. It will, however, make us poorer—economically and culturally—if it ends up stifling the voluntary and peaceful interactions that have made America great since its founding.