A Syrian woman holds her baby after their arrival on a small boat from the Turkish coast on the Greek island on Monday. (Santi Palacios/Associated Press)

IN THE face of the horror in Paris — not to mention Beirut and Baghdad — an instinctual reaction is to attempt to close the United States to the world and, in effect, ignore the plight of people America might help. At best, this reaction is understandable but self-defeating. From the mouths of Republican presidential candidates, it has become downright ugly.

The Post’s Jenna Johnson reports: “Former Florida governor Jeb Bush said Sunday that the United States should focus on ‘Christians that are being slaughtered.’ Sen. Ted Cruz of Texas said the country could continue to provide a ‘safe haven’ for Christians but not ‘refugees that may have been infiltrated by ISIS.’ Louisiana Gov. Bobby Jindal called for sealing off U.S. borders.”

At least 13 other governors — a majority of them Republican — have said they will close their states to Syrian refugees.

These arguments have some superficial appeal. One of the Paris bombers appears to have entered Europe through Greece, the same route that thousands of desperate refugees have taken to escape Syria’s brutal civil war. If a terrorist can take advantage of Europe’s willingness to accept refugees, isn’t the U.S. refugee program a serious security threat?

In fact, no. Europe is awash in Syrian refugees, its officials overwhelmed by the volume of people, nearly all of whom are simply seeking to survive. Germany alone may take 1 million people by the end of the year.

The United States, by contrast, is hardly more than a bit player in the refu­gee crisis, in part because it insists on an orderly and lengthy vetting process. The United Nations screens and then refers refugees to U.S. authorities, who work with Department of Homeland Security and intelligence officials to perform background checks and conduct interviews. Performing background checks on people coming from a failed state can be hard, but the program is set up to bring in the most vulnerable — the sick, the maimed, women, children and the elderly. Every step in the screening process reduces the risk.

So far, this vetting process has admitted fewer than 2,000 Syrian refugees into the country. President Obama’s plan is to take a mere 10,000 more next year. International humanitarian advocates scratch their heads over the backlash against taking even this small number. “There are many ways to come to the United States,” the International Rescue Committee’s David Miliband wrote in an op-ed. “Comparatively the refugee resettlement program is the most difficult short of swimming the Atlantic.”

Accepting only Christians would damage the country’s reputation and betray the notion that Americans are bound by common allegiance to laws, not creeds. These impacts would far outweigh the meager security benefits such an approach would provide.

The Paris attacks have shaken up the discussion on Syria. But the moral calculus regarding refugees who have been driven from their homes, beaten, tortured, gassed and raped hasn’t changed. The humanitarian necessity is overwhelming. Half of all Syrians have been displaced, and more than a quarter-million people have died. There is no excuse to sit by.