WASHINGTON—Hardly a week goes by that I don’t come into contact with an illegal immigrant somewhere in Washington, D.C. And this is by no means the area with the largest concentration of such immigrants in the United States. The stories are always compelling.

A few weeks ago, Rosita, a Bolivian in her late 40s, told me how on her journey to the United States, she was raped in Guatemala and swindled in Mexico, and how she had to cross the desert into this country after losing a brother who was killed because he refused to pay the “coyote” a larger fee than had originally been agreed. She then went through a health ordeal and was forced to have a hysterectomy in a low-cost clinic that helps immigrants. The operation went horribly wrong and she spent six months fighting for her life. Her two sons are in Bolivia, where she plans to return when she saves enough money to pay her debts. She works 12 hours a day, seven days a week, cleaning houses, doing errands for third parties, and baby-sitting. “In what way am I a criminal?” she asked me.

Of course, she has broken U.S. immigration laws. But she is, like 12 million other illegal immigrants, the victim of a gross illusion—the illusion that the laws of supply and demand can be obliterated by an act of political will. “Humankind cannot bear very much reality,” wrote T.S. Eliot in one of his quartets. He might have been talking about immigration in the 21st century.

The latest agreement between the White House and a bipartisan group of legislators notwithstanding, the emotional obfuscation that has replaced sensible thinking regarding this issue continues to make it very hard to expect a reasonable immigration bill in the middle of a presidential campaign.

Not even totalitarian societies have been able to root out social realities deemed undesirable—hence the pervasive alcoholism in Russia during the Soviet period. Whenever there is a disconnect between the law and reality, reality finds ways of making the law irrelevant. During most of the 300 years of its colonial era, Spain tried to impose draconian monopoly conditions on commerce in Spanish America. The result was that smuggling accounted for two-thirds of all trade in the colonies. Today, a number of Latin American constitutions make Catholicism the official church, and yet, as I mentioned in a recent column, in real life a plurality of religions has managed to penetrate the Latin American soul in recent decades.

It is always hard to oppose an emotional reaction with logical arguments and statistical evidence. Otherwise, the argument for the decriminalization of immigrants and a policy that helped match future demand for migrant workers with future supply would have been won long ago. In a country with an unemployment rate of 4.5 percent, who can seriously maintain that immigrants take jobs away from the natives? In a country where many of the states with the highest number of immigrants, such as New York and Florida, have unemployment rates below the national average, who can seriously accuse immigrants of displacing Americans? In a country where half a million immigrants come in illegally every year because the million that come in legally are not enough to match the high demand for foreign workers on the part of American businesses, who can seriously maintain that the immigration debate is mostly a debate between law-abiding Americans and law-breaking aliens?

And yet, these arguments would never persuade a politician such as Rep. Tom Tancredo, R-Colo., because he fears his constituents would never forgive him. The result is a colossal ideological inconsistency. Conservatism—and Tancredo calls himself a quintessential conservative—has always been pro immigration. From Edmund Burke, the Anglo-Irish philosopher and politician considered the father of conservative thinking, to Ronald Reagan, who had no qualms with the word “amnesty” when millions of immigrants were legalized under his watch in 1986, conservatives have understood that spontaneous social interactions and institutions are what make nations healthy, prosperous and peaceful. It is those social customs—and not bureaucracies detached from reality—that make the law. For conservatives, a real legislator is someone who pays close attention to social norms and tries to adapt to them.

“In what way am I a criminal?” asks Rosita, who does not have the least problem in finding an American willing to employ her every time she needs to change jobs, and who believes in hard work, thrift, family, and realistic laws.

The melancholy answer is: She is just a civil heroine ahead of her time.