Following the explosively controversial Moynihan report of the 1960s, “for nearly twenty years the policy and research communities backed away from the entire issue” of family structure, Barbara Dafoe Whitehead wrote in 1993. The Carter Administration’s 1980 White House Conference on Families—a rare attempt to raise the issue—turned into “a prolonged, publicly subsidized quarrel over the definition of family.” Twelve years later, then–Vice President Dan Quayle’s criticism of single mom (and sitcom character) Murphy Brown was greeted with derision. “In short,” Whitehead concluded, “every time the issue of family structure has been raised, the response has been first controversy, then retreat, and finally silence.”

While we continue to quarrel over marriage and the family, at least one facet of the debate is now nearly undisputed: that children do better, on average, when raised by their married parents than they do in other arrangements. Liberals denounced Dan Quayle two decades ago, but now they’re lining up to agree with him. As Jonathan Chait writes in New York Magazine, “The rapid growth of divorce and unwed motherhood has produced a huge increase in the proportion of American children being raised by a single parent, a vast social experiment with measurably harmful effects on children.”

“The cliché is true,” Matthew O’Brien agreed in The Atlantic: “Kids do best in stable, two-parent homes.” And no less a liberal icon than the New York Times’ Nicholas Kristof recently opined that conservatives are “correct to highlight family stability as a fundamental issue that goes to the welfare of children as much as food stamps or anything else.”

It’s heartening to see this growing consensus, even if we’re nowhere near agreement on how (or even whether) we can reverse the trend and mitigate its negative consequences. But there remains a danger of taking the selection effects that operate in marriage—that is, the truth that some apparent benefits of marriage arise because married people differ from unmarried people in aspects other than marital status—for the whole story. In recent days that mistake was stated most strongly in Steve Waldman’s claim that “neither wedding cake nor the marriages they celebrate cause observed ‘marriage premia’ any more than dances on tarmacs caused airplanes to land on Melanesian islands.”

For now let’s set aside the considerable amount of contrary evidence showing that, according to the most advanced possible research methods and even when major background factors are accounted for, marriage does seem to have causal effects on income, health, and child outcomes and concentrate on a related error: Attributing marriage premiums entirely to selection effects entails a strongly deterministic view of humanity. And Waldman seems to lean toward that view, to judge by sentences like “people in actually observed marriages do well because they are the lucky ones to find scarce good mates” and “the pool that’s left over, once all the people capable of signaling their membership in the socioeconomic elite have been ‘creamed’ away, may often be, objectively, a bad one.”

As Amy Wax wrote about this view in another context,

Setting aside the differences among families that social scientists already control for or that policies might be able to improve, the assertion that outcome differences are really due to selection suggests that the reason unconventional families are more troubled is that the people within them are more troubled—and inherently so. But if this is what really makes the difference, neither marriage, nor more resources, nor better government policies will [make these families equal to others]. . . .

[Do selection-effect proponents] really buy into this counsel of despair? [Do they] really want to embrace the position that failure to marry is, in effect, a marker of weak character and a defective personality? Is marriage now the redoubt of society’s intrinsically successful, with the hapless and maladaptive relegated to “diversity”? The implications of this position are staggering.

Consider that approximately sixty-nine percent of black children are now born out of wedlock. If the problems documented for these children, as compared to those with otherwise similar but married mothers, are really due to “selection,” this means that their greater difficulties are traceable to the fixed traits of their biological parents. This is equivalent to saying that sixty-nine percent of black children are effectively destined to inferior outcomes by their parents’ personal shortcomings.

Waldman is right about certain things, such as the factors that make poor women hesitate to tie the knot. Merely telling single people to marry without helping them attain the financial stability, relationship skills, and beliefs that make marriage work would indeed be harmful. But his apparent suggestion that large numbers of Americans are simply and inevitably not capable of building happy, stable marriages—albeit for reasons beyond their control—is an insulting and untenable claim. Between cultural and economic factors, and the legacy of racial discrimination, the marriage pool is indeed poor in certain communities. But it doesn’t have to be. Bottom line: Marriage need not be the preserve of rich people.