It is understandable that Donald Trump's vulgar attack on immigrants has nicer people up in arms, and that pundits are leaping to their computers to chastise Ben Carson for saying he might not want a Muslim to be president of the United States. But it wouldn't be a bad thing if these comments opened the question of American immigration policy to review. 

Preparing to assimilate: Ellis Island, 1905

     We must begin by dismissing the notion that our previous experience with immigration teaches us lessons applicable to the current infl ux, especially if that is to be composed mostly of thousands of young Muslim men, some of them fl eeing Syria. Our past immigration history is not prologue. 

    My father came to this country as a boy at a time when there was no welfare state to offer the lure of a bene- fi ts-supported life. The establishment of the welfare/entitlement state has provided an incentive to come here that simply did not exist earlier in our history. Add a relaxed policy towards illegal arrivals-from Ronald Reagan's amnesty to Barack Obama's Hispanic dreamers and nonenforcement of the law against other illegal border crossers-and you have an irresistible magnet to groups believing what my father was told but did not believe, that the streets of America are paved with gold.   Now when a welfare state rolls out the welcome mat to asylum-seekers, it can expect it to be trod on by economic migrants as well, as German chancellor Angela Merkel has discovered. Her decision to announce that Syrians would be welcome in the millions, and need not obey the rules requiring registration in the first EU country in which they touched down, has left her with the daunting task of separating legitimate asylum seekers from seekers after housing and other benefits, many of the latter having destroyed their passports and claiming to be from Syria when instead they come from countries in which their lives are not threatened. 

     My father came to a country desperately in need of unskilled labor, a circumstance that no longer exists: Millions of unskilled Americans fi nd themselves members of the reserve army of the unemployed and are so discouraged by their inability to fi nd work that they have dropped out of the job market. And studies by Harvard professor George Borjas show that immigrants put pressure on the wages of unskilled Americans, which of course is one reason employer groups favor more immigration and many trade unions a lot less.

     My father came to an America that had not yet been affl icted with multiculturalism. He came in order to become an American. As did millions of Irish, Italians, Eastern Europeans, and others. All wanted to preserve some of their historic culture, and they did cling together in ghettoes early on, before dispersing as their incomes grew.

    But the experience of Muslim immigrants, with Britain and France the prime examples, is different. Muslims did not come to Britain to assimilate. Many seek to retain not only their customs but some version at least of their system of sharia law, of subjugation of women, of forced marriages. In France, Muslim ghettoes have become no-go zones for the police. My father left Poland behind, the Irish said goodbye to Ireland's privation, Italians to lack of opportunity in Italy. But for Muslims the organizing institution is not the nation-state, which they are leaving behind, but their religion, which most are bringing with them.

     In America, defenders of Muslim immigration are quite right to say that many are nice people and would enrich this country. But it is not unreasonable to suppose that the portion coming here to sing not "God Bless America" but "God Damn America," and to hasten the day when the damning occurs by blowing us up, is likely to be higher in this group than among other groups applying for admission. And yes, there were some really bad actors among the older immigrants, as you can learn from studies of Jewish and Italian gangsters. But those were your garden-variety bad guys, primarily killing each other and not aiming to blow up Ellis Island or the Empire State Building.

    And there really is no good way to separate the wheat from the chaff. Terrorists do not arrive here wearing signs identifying them as the sort who waltzed through airport security to crash airplanes into the World Trade Center. Security since then has tightened, but inspectors in 67 of 70 test cases managed to get through Homeland Security procedures armed with weapons and explosives. So John Kerry's promise of rigorous screening of the thousands of Syrian immigrants he and the president are volunteering to allow to jump the immigration queue must be laid against the inability of Homeland Security to accomplish its most basic objective. It would be interesting to hear from our secretary of state why thousands of Muslims are being given precedence over the more pacific and certainly more endangered Christians in deciding who gets to jump the immigration queue.

     Were immigration policy to be determined by economic criteria, life would be simple: Admit those most likely to add to the national wealth of existing residents, the solution adopted in Canada and Australia. That works fi ne in individual cases. But not when dealing with waves of immigrants such as those descending on America and Europe, immigrants not under the pressure earlier waves felt to assimilate. The social costs of immigration, like so many others imposed on society by progressive policies, are borne by those least able to afford them-the middle-class families who cannot afford to send their kids to private schools but watch helplessly as their educational progress is slowed by the children of illegal immigrants who cannot speak English; the lowerincome families for whom emergency rooms are the first line of defense against illness and physical misfortune, who find them overcrowded with immigrants; the unskilled workers whose wages are depressed by competition from newcomers, many willing to work at below legal wage rates because they are still so much better off than they were at home.

     We are a generous and welcoming people, still believers in what the Lady in the Harbor has to say. But not all huddled masses are equally yearning to breathe free. And it's not bigotry to ask some hard questions before we throw the gates open.