By James Heffernan

Xenophobia is a Greek word meaning “fear of strangers.” Fear of immigrants, foreigners, aliens — anyone who does not look lke us or belong to our tribe. Fear of the other.

More than anything else, it was xenophobia that gripped Robert Bowers, the 46-year-old truck driver now charged with killing 11 people and wounding six more at the Tree of Life Congregation synagogue in Pittsburgh.

Consider the final message Bowers posted on Gab, a website that freely welcomed both anti-Semites and xenophobes: “HIAS likes to bring in invaders that kill our people. I can’t sit by and watch my people get slaughtered. Screw your optics, I’m going in.”

Roberts’ final rant needs a little unpacking. “Optics” means efforts to make white supremacy look respectable. HIAS (www.hias.org), whose motto is “Welcome the stranger. Protect the refugee,” is the Hebrew Immigrant Aid Society, which for 140 years has been helping to resettle not just Jewish immigrants but refugees of all denominations.

Among the more than 4.5 million people who have escaped persecution with its aid is a Russian immigrant named Sergey Bin, co-founder of Google, which employs more than 85,000 people. Does he sound like a murderous invader?

HIAS has also aided Muslim refugees such as Mazen Hasan, an Iraqi engineer whose life was threatened because he had worked for the American military in Iraq.

Such kindness can breed more kindness in return. In less than a week after the Pittsburgh massacre, two Muslim organizations have raised nearly $200,000 to help the victims and their families. Would we really all be better off if President Donald Trump had managed to impose a “total and complete shutdown of Muslims entering the United States,” as he promised during his campaign for the presidency?

I do not mean to argue that the Pittsburgh shooter was acting for the president. Unlike Cesar Sayoc, the Florida pipe bomber who flaunted his devotion to Trump in posters plastered all over his white van, Robert Bowers thought Trump was not xenophobic enough.

Commenting on Trump’s claim to be a nationalist, Bowers wrote, “Trump is a globalist, not a nationalist. There is no MAGA” as long as there is an “infestation” of Jews, he wrote, using a slur. Among far-right anti-Semites, “globalist” has long been a synonym for “Jewish,” for even though the Jewish people now have a nation of their own, their international identity as a dispersed people has made nationalists see them as aliens — “invaders” just as bad as the would-be murderous refugees they help.

But even though Trump is not xenophobic enough for the Pittsburgh killer, he has made himself the reigning voice of xenophobia in this land. He launched his presidential campaign by claiming that Mexican immigrants were criminals and rapists, and he has never ceased to demonize immigrants from Latin America and Muslim countries.

In doing so, he tramples on facts. He made his first claim about Mexican immigrants in June 2015.

During that same year, a study by the Cato Institute found that undocumented immigrants in Texas committed less than half the number of crimes committed by native-born citizens, and that legal immigrants in Texas committed less than one-seventh.

Let’s get this straight: As a group, immigrants make us safer. They work hard, obey the law, create jobs, pay taxes, and altogether give much more than they get in education and social services. But Trump cannot tolerate such facts — or any facts that challenge his xenophobia. On the contrary, he now insists that the caravan of Central American migrants headed for the U.S.-Mexico border “is an invasion and our Military is waiting for you!”

An invasion? According to Newsweek, the Pentagon estimates that the present caravan of roughly 7,000 people will dwindle to fewer than 1,500 by the time they reach the border and will present no credible threat.

Yet to meet this unarmed crowd of families merely hoping to exercise their legal right to apply for asylum, Trump will not rely on the more than 16,000 border guards (most of them Latinos) already on duty down there, or even on the roughly 2,100 National Guard troops he sent earlier this year.

Instead, he is sending at least 5,000 and perhaps as many as 15,000 active duty troops — at a cost that could reach $50 million. According to U.S. intelligence assessments, the only real threat they will face is from an “estimated 200 unregulated armed militia members currently operating along the southwest border (and) ... stealing National Guard equipment.”

So why does Trump treat the migrants as enemy invaders? The only plausible answer is that doing so fuels the xenophobia of his base, which he sought to inflame as the midterm elections approached.

In addition, he has vowed to sign an executive order ending the 14th Amendment’s guarantee of birthright citizenship for all children born in the United States, whether their parents are citizens or not.

By thus amending the U.S. Constitution all by himself, Trump thinks he can make xenophobia the law of the land — and make the Department of Justice enforce this law.

In June, Attorney General Jeff Sessions cited scripture to justify the policy of breaking up immigrant families — tearing children, even babies, from the arms of their mothers and fathers to deter the families from coming here. In Boston last Monday (two days before he was fired by Trump), just as he began a speech on “The Future of Religious Liberty” at a meeting of the conservative Federalist Society, Sessions was interrupted by a United Methodist minister who stood up and paraphrased the New Testament. “Remember the words of Jesus,” said the Rev. Will Green. “ ‘I was hungry and you did not feed me. I was a stranger, and you did not welcome me.’ ”

“Brother Jeff, as a fellow United Methodist, I call upon you to repent, to care for those in need, to remember that when you do not care for others, you are wounding the body of Christ.”

As Sessions thanked Green for his remarks and “attack,” police removed the minister. So much for religious liberty — and freedom of speech.

To demonize immigrants is not just to violate the Christian principles that so many American politicians profess to uphold. It is also to forget that we are a nation of immigrants.

Let us not become a nation of xenophobes.

James Heffernan, of Hanover, is a professor emeritus of English at Dartmouth College. His latest book is Hospitality and Treachery in Western Literature.