Ryan’s position has a long conservative pedigree. He has followed in Jack Kemp’s intellectual footsteps. He can cite Ronald Reagan as well. The Wall Street Journal editorial page that championed Kemp and Reagan’s tax cuts also called for open borders. Republicans like Ryan tend to see America as a proposition or an idea, defined by the political principles laid out in the Constitution and Declaration of Independence.

In this telling, immigration affirms the truths we hold to be self-evident, particularly that all men are created equal and the unalienable right to the pursuit of happiness. The willingness of immigrants to come here is a testament to the success of those principles. “Immigration,” writes veteran conservative columnist George Will, “is the entrepreneurial act of taking the risk of uprooting oneself and plunging into uncertainty.”

Restricting immigration, according to these Republicans, isn’t conservative because it requires government bureaucracies to interfere in labor markets. Immigration is like free trade and restricting it is like protectionism.

Adherents of the other immigration view tend to see America as a historic people, not an ideological abstraction. They also look at immigration as the pre-eminent national security issue. They may not go as far as Trump, but they worry less about the Islamic State in Iraq and Syria than the Islamic State in San Bernardino.

According to this side of the argument, too much immigration can also alter the political character of the host country.