The half-century between 1912 and 1962 was a period of great wars and economic tumult but also of impressive social cohesion. Marriage rates were high. Community groups connected people across class.

In the half-century between 1962 and the present, America has become more prosperous, peaceful and fair, but the social fabric has deteriorated. Social trust has plummeted. Society has segmented. The share of Americans born out of wedlock is now at 40 percent and rising.

As early as the 1970s, three large theories had emerged to explain the weakening of the social fabric. Liberals congregated around an economically determinist theory. The loss of good working-class jobs undermined communities and led to the social deterioration.

Libertarians congregated around a government-centric theory. Great Society programs enabled people to avoid work and gave young women an incentive to have children without marrying.

Neo-conservatives had a more culturally deterministic theory. Many of them had been poor during the Depression. Economic stress had not undermined the family then. Moreover, social breakdown began in the 1960s, a time of unprecedented prosperity. They argued that the abandonment of traditional bourgeois norms led to social disruption, especially for those in fragile circumstances.

Over the past 25 years, though, a new body of research has emerged, which should lead to new theories. This research tends to support a few common themes. First, no matter how social disorganization got started, once it starts, it takes on a momentum of its own. People who grow up in disrupted communities are more likely to lead disrupted lives as adults, magnifying disorder from one generation to the next.

Second, it’s not true that people in disorganized neighborhoods have bad values. Their goals are not different from everybody else’s. It’s that they lack the social capital to enact those values.

Third, while individuals are to be held responsible for their behavior, social context is more powerful than we thought. If any of us grew up in a neighborhood where a third of the men dropped out of school, we’d be much worse off, too.

The recent research details how disruption breeds disruption. This research includes the thousands of studies on attachment theory, which show that children who can’t form secure attachments by 18 months face a much worse set of chances for the rest of their lives because they find it harder to build stable relationships.

It includes the diverse work on self-control by Walter Mischel, Angela Duckworth, Roy Baumeister and others, which shows, among other things, that people raised in disrupted circumstances find it harder to control their impulses throughout their lives.

It includes the work of Annette Lareau, whose classic book, “Unequal Childhoods,” was just updated last year. She shows that different social classes have radically different child-rearing techniques, producing different outcomes.

Over the past two weeks, Charles Murray’s book, “Coming Apart,” has restarted the social disruption debate. But, judging by the firestorm, you would have no idea that the sociological and psychological research of the past 25 years even existed.

Murray neglects this research in his book. Meanwhile, his left-wing critics in the blogosphere have reverted to crude 1970s economic determinism: It’s all the fault of lost jobs. People who talk about behavior are blaming the victim. Anybody who talks about social norms is really saying that the poor are lazy.

Liberal economists haven’t silenced conservatives, but they have completely eclipsed liberal sociologists and liberal psychologists. Even noneconomist commentators reduce the rich texture of how disadvantage is actually lived to a crude materialism that has little to do with reality.

I don’t care how many factory jobs have been lost, it still doesn’t make sense to drop out of high school. The influences that lead so many to do so are much deeper and more complicated than anything that can be grasped in an economic model or populist slogan.

This economic determinism would be bad enough if it was just making public debate dumber. But the amputation of sociologic, psychological and cognitive considerations makes good policy impossible.

The American social fabric is now so depleted that even if manufacturing jobs miraculously came back we still would not be producing enough stable, skilled workers to fill them. It’s not enough just to have economic growth policies. The country also needs to rebuild orderly communities.

This requires bourgeois paternalism: Building organizations and structures that induce people to behave responsibly rather than irresponsibly and, yes, sometimes using government to do so.

Social repair requires sociological thinking. The depressing lesson of the last few weeks is that the public debate is dominated by people who stopped thinking in 1975.