There are many solid arguments for why the United States should not grant legal status to unauthorized immigrants, as opponents of immigration reform, have argued for years now.
But as the debate continues to rage, one particular mantra is heard from opponents of legalization, perhaps more consistently than any other:
"My ancestors came here legally."
So too, the argument holds, must today's immigrants. We're a nation of laws, we must be consistent, and we must not reward law breakers.
It's a mighty handy argument that worked wonders for opponents of the legalization bills that have died in Congress over the past two decades. It's logical, and draws a clear moral distinction between previous generations of law-abiding immigrants and today's border-jumpers. It heads off allegations of xenophobia, allowing the speaker to say it's not immigrants he or she is against, just illegality.
It works, too, because it rings true with Americans. The images burned into our brains of previous immigration waves come largely from newsreels and photos of immigrants disembarking at Ellis Island, one at a time, orderly, legally.
There's one problem with the argument. It's utter hogwash.
First of all, for hundreds of years, as immigrants poured in by the hundreds of thousands from the 1600s to the early 1900s, there were simply no federal immigration laws to break.
Unless you were a criminal or insane (or after 1882, Chinese), once you landed here, you were legal.
Crediting yesteryear's immigrants with following the laws is like calling someone a good driver because they never got caught speeding on the Autobahn.
"Only 1 percent of people who showed up at Ellis Island were turned away," said Mae Ngai, author of "Impossible Subjects: Illegal Aliens and the Making of Modern America."
"What that statement is ignorant of is that we didn't always have restrictions. It's a fairly recent phenomenon."
Level the playing field hypothetically, and the argument becomes even more preposterous.
Imagine today's immigration laws, which make it impossible for most poor foreign farmers to immigrate legally -- in effect in, say, 1849.
Somewhere in Ireland, a starving farmer turns to his family, their mouths green from eating grass in the midst of the potato famine.
"We could escape to America and have food to eat," the farmer says. "But I'd never do that without a visa. That would be a violation of U.S. immigration law."
Ridiculous, of course. That farmer would have done exactly what today's Mexicans, Chinese and Guatemalans are doing by the millions -- get to the United States so they can feed their families, and worry about getting papers later.
Which brings us to the second reason the "my ancestors came legally" argument is absurd.
It's because lots of people's ancestors simply didn't.
Once Congress put immigration quotas in place to keep out less desirable Eastern and Southern Europeans in 1921, they began sneaking in by the thousands.