It's hard to shake the feeling that eugenics can make a comeback. Or that it never really left us.

When Supreme Court Justice Ruth Bader Ginsburg gave a recent interview to Elle, she let slip a statement that almost sounded like something a 1920s-style eugenicist would say. Talking about the rise of state-level restrictions on abortion, the liberal justice said, "It makes no sense as a national policy to promote birth only among poor people."

And remember, a few years ago, Ginsburg had to deny that she believed eugenic thought influenced the Supreme Court's Roe v. Wade decision. She had noted a prevailing concern about population growth at the time of the decision, "particularly growth in populations that we don't want to have too many of."

That Ginsburg had to disavow the plain meaning of her earlier words is a good sign that people are repulsed by eugenics of a certain type. We simply would not tolerate a modern Supreme Court justice with the cut of Wendell Holmes, who wrote in 1927's Buck v. Bell: "It is better for all the world if, instead of waiting to execute degenerate offspring for crime or to let them starve for their imbecility, society can prevent those who are manifestly unfit from continuing their kind. The principle that sustains compulsory vaccination is broad enough to cover cutting the Fallopian tubes. Three generations of imbeciles are enough." Southern states have recently compensated victims of their own Holmes-inspired sterilization laws. So much history, gladly forgotten. Right? Well, not necessarily.

Eugenics has hung around. In response to Ginsburg's quotes, people have rediscovered Ron Weddington, co-counsel in Roe and a man who advised Bill Clinton to make abortifacients universally available with these words: "You can start immediately to eliminate the barely educated, unhealthy, and poor segment of our country. It's what we all know is true, but we only whisper it."

The idea that it will be criminals and the unhealthy who are aborted or birth-controlled out of existence has persisted in less explicitly racial terms for some time. Economists Steven Levitt and Stephen Dubner made a case in the wildly popular Freakonomics that the ever-lowering crime rate their big-city audience was experiencing was due to legalized abortion. It wasn't a eugenic argument for abortion, just a convenient eugenic side effect. Indeed, 41 percent of all pregnancies in New York City ended in abortion in 2010, although the rate was lower in Manhattan than in the Bronx, where certain "populations" are more concentrated. Somewhere in hell, Holmes smiles.

In the case of babies with Down syndrome, we are already eugenicists. In the late '90s in Europe, 92 percent of unborn children diagnosed with Down syndrome were terminated by abortion. The number is lower in America, according to some local studies. In an article that explores this sympathetically, Alison Piepmeier writes:

Repeatedly women told me that they ended the pregnancy not because they wanted a "perfect child" (as one woman said, "I don't know what 'perfect child' even means") but because they recognized that the world is a difficult place for people with intellectual disabilities. [The New York Times]

If the numbers on abortion and Down syndrome are even remotely accurate, the birth of a Down baby is something already against the norm. As medical costs are more and more socialized, it is hard to see how the stigma attached to "choosing" to carry a Down syndrome child to term will not increase. Why choose to burden the health system this way? Instead of neighbors straightforwardly admiring parents for the burden they bear with a disabled child, society is made up of taxpayers who will roll their eyes at the irresponsible breeder, who is costing them a mint in "unnecessary" medical treatment and learning specialists at school. Why condemn a child to a "life like that," they will wonder.

Ultimately, Piepmeier says we should make it easier for women to bring children into the world. Bully for that. But the fact that "the world is a difficult place" for some people more than others is a problem unsolvable by social and political reform or medicine. How much poorer, how much more pre-disposed to a disease, how much more socially detested does one have to be to be beneath this eugenic hurdle for existence?

All the ingredients still exist for a more explicit return to eugenics in our culture and politics: inequality, fear, detestation of the other. But if it comes back, it is unlikely to come in the explicitly racialist terms of the biodiversity-obsessed right. Liberal societies have the antibodies against that.

Instead, it will come to us in terms of "quality of life," and "health and safety." We will be urged that every child deserves the best society can grant, and stigmatize those for whom "the world is a difficult place." And thereby we legitimize the destruction of those who would merely "live" in society rather than thrive in it.