If only wishing could make things so. If it did, Mark Krikorian would be in a great position. We don't need immigrants, he maintains. We can stop them coming. We can even wage a war of attrition against those already here until we've reduced the foreign-born population to . . . I don't know, maybe the vanishing point.

The problem is none of this true.

"Reduce the number of illegals coming in and increase the number leaving," he suggests glibly. Well, the U.S. government tries very hard to do just that, and has been trying harder than ever, with vastly increased resources, over the past 15 years. The number of agents on the border has more than doubled. The INS has orchestrated workplace raids to flush out illegal workers. Congress has barred all immigrants, legal and illegal, from most entitlement programs — hoping, just as Mark Krikorian suggests, that this would drive many to return home.

Yet none of this has made any appreciable difference. Agents gain control of one stretch of the border only to find that migrants go elsewhere, crossing at another stretch. Employer sanctions are met with protests, not just from employers but from entire communities where foreign-born labor keeps plants and other businesses open, generating jobs and income for Americans. Most intractable, despite all the effort, the number of entrants has changed little. Just over a million still come each year — and the share arriving illegally is slightly larger.

Nor is this reliance on foreign labor necessarily bad for the economy. Just look at Japan, which has pursued an alternative course, effectively barring immigrants and automating to increase productivity. That seemed like a good choice through the 1980s, but now much of the Japanese car industry is moving elsewhere in Asia, where labor is more plentiful. So too, in the U.S., farmers deprived of immigrant workers might use more machines or grow different crops — or they might just move to another country, like Mexico, where they can find the hands they need. True, some jobs can't be exported — but in that case too, the economy suffers if the labor flow is restricted. Just try hiring a babysitter or a nurse's aide in Tokyo.

Of course, in today's world, economic considerations are and must be secondary. If it really were a choice, as Mark Krikorian suggests, between cheaper produce and American security, no one would even pose the question and we wouldn't be having this debate. But that isn't the choice. We can have security and remain connected to the world, too. Most of the war against terror ought to take place beyond our borders, using military means and intelligence to stop evildoers before they arrive at our shores. Then, when it comes to immigration, the key is recognizing the reality of how many are coming, creating legal channels for those we can vet easily and focusing resources — money, agents, technology and the rest — on the much smaller number who might conceivably do us harm.

This isn't utopianism, as Mark Krikorian claims — it's realism. And it isn't just one option among many for dealing with the immigrant flow. In the age of global terrorism, it's the only safe way. Pretending we can reduce the influx will have the opposite effect, driving more of it underground and enlarging the shadowy population that lives in America but outside the law, traveling on false papers, driving without licenses, banking outside the financial system and otherwise evading regulation. Is Mark Krikorian really so intent on reducing the immigrant presence that he favors endangering the nation in that way?

— Tamar Jacoby is a senior fellow at the Manhattan Institute and author of Someone Else's House: America's Unfinished Struggle for Integration.

I have long considered buying a voicemail system, so that when people would call, a pleasant voice would say, "This is the Center for Immigration Studies. If you think immigrants take jobs Americans won't do, please press 1 now."

There are plenty of other myths in the debates over immigration, but this is perhaps the most ridiculous — so divorced from the realities of market economics that it's more suited to the pages of Mother Jones than National Review. Tamar falls for this when she asks "who then would man our farms? . . . Who would do the dirty jobs in hotels and restaurants? Where would we get nurses?"

There is no such thing as a "job Americans won't do," because the economy is not a static object but rather a dynamic system that responds to change. If immigration were reduced, and not enough Americans were willing to take those jobs at existing wages, two things would happen, at the same time: 1) Employers would seek to attract new workers, through higher wages, more benefits, and better working conditions, and 2) Employers would seek to eliminate the jobs they were now having trouble filling, through mechanization and more-efficient use of the remaining labor. In other words, the poor would get a raise (organically, through the workings of the market) and those sectors now dependent on foreign labor would become more productive. What's more, since the total output of all unskilled workers, immigrant and native, doesn't amount to more than four percent of GDP, a modest increase in the cost of unskilled labor would have no measurable effect on inflation rates.

Another myth that enthralls high-immigration advocates is that the flow of immigrants is inevitable — "that busboy is going to come anyway," as Tamar claims. So, these advocates argue, we'll be better off if we just lie back and pretend to enjoy it, finding some way to manage a phenomenon we are powerless to influence.

In fact, there is nothing inevitable about immigration; it is an artifact of government policy. No one wakes up in Bolivia and says to himself, "Today, I will move to Hoboken!" People migrate to places where they have networks of relatives, friends, acquaintances, countrymen, and these networks are created by the state. You can see how this works by comparing the Philippines and Indonesia. Both are poor, populous countries on the other side of the world, and yet we have more than one million Filipino immigrants, but no Indonesians. Why? Because we ruled the Philippines for 50 years, and kept major bases there for decades longer, establishing the networks that make immigration possible, while we never had anything to do with Indonesia.

Most Mexican immigration, for instance, still comes from several states in the west-central part of the country — the very states where opposition to the Mexico City regime was centered in the 1920s and '30s and where the Mexican government encouraged people to head north for work rather than demand democratic reforms. Our Bracero Program, which brought hundreds of thousands of "temporary" farmworkers over a 20-year period ending in the early '60s reinforced those networks, and then the big illegal-alien amnesty passed by Congress in 1986 refreshed them yet again.

The networks created by government policy can be interrupted by government policy, albeit with more difficulty. If we are ever to have control over our borders we need to weaken these ties, so they atrophy over time, and not create new ones through the kind of guest-worker amnesty that the White House is pushing. "Regularizing" illegals would only supercharge illegal immigration, from Mexico and elsewhere, making it that much harder to secure our homeland against the enemy.

— Mark Krikorian is executive director of the Center for Immigration Studies.