Much about the future health of the republic depends on Harvard sociologist Robert Putnam being wrong. Given the track record of Harvard social scientists, this might appear a reasonable bet. But, in this case, Putnam’s diligence and thoughtfulness make for very bad news.

Putnam has spent much of his academic life as America’s chief chronicler of declining social institutions — a dour task, cheerfully performed. In the 1990s, he began drawing together the disparate evidence of declining attendance at bowling leagues, church services and Moose lodges. His data points included the falloff in yearly picnic attendance and a rise in the incidence of drivers giving each other the finger.

It was the composite image of one of the most powerful forces of modernity: a rising individualism that “liberates” people from social commitments that make their lives orderly and pleasant.

Even worse, the extent of this trend is not distributed equally in society. Putnam’s recent work — to be summarized in a forthcoming book called “Our Kids” — focuses on how the consequences of institutional decline are felt disproportionately among the working class, leaving vast numbers of youths disconnected from the promise of American life.

Upper- and middle-class parents are investing relatively more time and resources in the social development of their children than are working-class parents, at a time when such investments have never been more economically strategic. This widening gap can be measured in parental play and reading time with young children; later, in the engagement of older children in extracurricular activities. Suburban minivans are occupied in taxiing children to tutoring, sports, clubs, youth groups and volunteer activities. By these measures, children from working-class backgrounds are falling behind.

The problem is that early social connectedness is a strong predictor of later success in life — test scores, college attendance and income. So what Putnam calls the “youth class gap” is a source of deep (and perhaps deepening) social division.

Much of modern liberalism — recently inspired and incited by Thomas Piketty’s book “Capital in the Twenty-First Century” — is focused on growing income inequality. And surely, at some eventual point along an unbroken trend of increasing returns to capital and diminishing returns to wages, the rich and poor will cease to be fellow citizens in any meaningful sense. But what is most striking about a disproportionate emphasis on income inequality is how distorting and distracting it is.

If income inequality is the main economic problem, it could be solved tomorrow, through confiscation and redistribution. If the main problem is the unequal generation of social capital in institutions such as families, schools and communities, the solutions get more difficult. One task can be accomplished by a tax collector; the other is the work of a civilization.

Putnam’s analysis both illuminates the complexity of public policy choices and increases the likelihood that policy solutions could gain broad political support. His proposed explanations for the disproportionate decline in social connectedness among the working class are ideologically diverse. “Decreasing social mobility,” he argues, “represents a perfect storm with multiple, interrelated causes, such as [a] widening income gap and increasing economic insecurity for working-class households, changes in the working-class family structure, [and the] unraveling of the informal social safety net in working-class neighborhoods.”

These arguments are rooted in observation rather than ideology. But they create the possibility of ideological consensus, or at least of ideological compromise. Proposals focused mainly on reducing income inequality require the political triumph of the left. Conservatives, being conservatives, will not concede leveling as a valid economic goal. But an agenda that increases the rewards of work, encourages stable, engaged families and promotes healthy community institutions could be a shared political enterprise.

Put another way, an abstract argument between advocates of economic liberty and advocates of economic equality can only be settled by victory for one side. The goal of building social capital can (at least in theory) be a virtuous competition. It might include a range of approaches: increasing the earned-income tax credit for single workers (who are often non-custodial parents); working to reduce non-marital births; promoting broader access to higher education; encouraging mentoring; increasing the child tax credit.

The goal of this approach would be to strengthen the social institutions — education, family, work — that strengthen social mobility. And this might have a chance of decreasing the polarization of our economy and the polarization of our politics.

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