A minor scuffle has broken out among several conservative and liberal bloggers about the meaning of eugenics and its connection (if any) to today’s progressive movement.

No one questions the link between the progressivism of a century ago and the eugenics movement (or almost no one: Washington Monthly‘s Kevin Drum seems never to have heard of it). The eugenics movement understood itself to be improving the human future by enlightened and scientifically informed intervention. As a progressive cause it was ideal, and was championed to varying degrees by nearly every prominent American progressive. That doesn’t mean the progressives of today would support it. But to the extent that they want to identify explicitly with the original progressive movement, they probably should contend with it.

Today, a rather different sort of effort to apply control and selection over the next generation is emerging, in the form of a growing inclination to test developing human embryos and fetuses for ailments and weaknesses (or even just the wrong sex), and to eliminate those found to bear them. The trend itself is undeniable. Ninety percent of Down’s syndrome pregnancies are aborted, for instance. And according to one recent study, “40 percent of infants with any one of 11 main congenital disorders were aborted in Europe.”

But is it reasonable to call this new attitude eugenic? Some advocates employ the term, as do many critics on the left and right. But this new trend differs enormously from the eugenics of a century ago: it is not coercive or enforced by government; it is not based on race distinctions or assessments of intelligence or social class; it is often (though not always) carried out by parents, when they find their child has a condition they believe would be a grave detriment to his or her welfare or happiness.

But surely the most essential problem with the eugenics movement was not coercion or collectivism. It wasn’t even the revolting notion of some duty to improve the race. The deepest and most significant contention of the progressive eugenicists was that science had shown the principle of human equality to be unfounded. These eugenicists badly misread Darwin. The eugenicists of today, in contrast, employ actual scientific principles to support their beliefs; nevertheless, their abuse of science is no less misguided. It is, again, being used to demonstrate distinctions among human beings that—the new eugenicists claim—are so fundamental as to make some lives not worth living, and therefore not worth protecting.

The challenge of eugenics was, and is again, a challenge to our egalitarianism. That is what lies at the heart of the abortion debate, and of the larger debate about emerging biotechnologies. These arguments are not about when a new human life begins—an empirical matter not in real dispute—but about whether every human life is equal. That question is a perfectly serious one, and there are defensible positions on both sides. But too many American progressives have answered in the negative without thinking through the consequences. And increasingly the reasons they give are not liberal reasons—reasons of liberty and personal choice—but scientific reasons, be it the great promise of some very particular avenue of medical research, or the instrument readings that demonstrate Down’s or another genetic condition.

These progressives are, in this sense, new eugenicists. That doesn’t mean they would abide Nazi medicine or forced sterilizations. But it does mean they abide scientific selection to eliminate the weakest among us.