"Good fences make good neighbors." Nearly all of us have heard that expression, and some of us know that it was part of Mending Wall, a poem by Robert Frost. Most of us also know what it means — that some modest barriers between houses and people are essential to a healthy community life. Not as many of us are aware that in the same poem, in the very first line, Frost made an opposite declaration: "Something there is that doesn't love a wall." It turns out that the poem is about a dispute between two adjoining property owners. One of them wants to build the fence; the other, presumably Frost, finds it unnecessary and likely to be offensive.

That poem has been analyzed almost to death by literary critics, but if you think about it broadly, it says a great deal about the way we live, not just as property owners but also as members of society. Our social and political lives are steeped in conflict between a desire to break down barriers and a desire to create more of them and protect our privacy. In some periods, one of these ideas predominates; sometimes it's the other. But the larger issue of walls versus openness never really goes away. Indeed, we typically find ourselves putting up new walls just at the moment we are tearing others down.

There isn't much doubt that the past few decades in America have seen a triumphal movement for de-walling our lives, symbolized most graphically by the massive barricading freeways we have demolished to popular applause in Boston, Milwaukee, San Francisco and other cities, turning ugly bastions of concrete into parks, playgrounds and waterfront promenades.

This movement, which has gained new strength in the last few years, is the physical representation of the idea that walls are bad and openness is good. We have not only tilted toward openness in city planning, we have done it in the design of the places where we live and work as well. "Over the past few decades," Amanda Mull wrote perceptively in The Atlantic recently, "the formerly subdivided interior spaces of work and home got a lot more open."

The fads that we embrace in private design inevitably find their way into public design. In the 1970s, some of our biggest cities began moving their governments into enormous new city halls with open atriums extending from floor to roof, and offices stretching along open corridors on the upper floors, each of them with a clear view all the way down to the lobby below. Many of them were surrounded by vast concrete plazas on the outside, usually bare and windswept and rarely used by the public.

The Dallas City Hall, designed and constructed on an open plan in the 1970s, was one of the pioneers, an avant-garde atrium structure by I.M. Pei that was generally well received. The James R. Thompson Center, a state office building in Chicago, was not so successful. Its immense atrium and the free-flowing design on all 17 of its floors were meant, in the words of one of its creators, to carry the message of "an open government in action." Its inhabitants found it awkward to use, frigid in winter, and prone to an occasional suicide jump from one of the open walkways on the upper floors. Boston's City Hall, widely touted as a groundbreaking architectural achievement when it opened in 1968, never had much credibility with the public, and even less after 2001 as security barriers replaced many of the open-plan community spaces.

IT ISN'T JUST CIVIC ARCHITECTURE that has expressed the urge to do away with walls. Mayor Michael Bloomberg's management style in New York City in the 2000s was epitomized by a bullpen office design that largely did away with private offices and placed all the important managers, including Bloomberg himself, at desks in the middle of a sprawling barnlike interior that looked more like a Wall Street trading floor than a government office. "You don't have to peel back the layers to get into the inner sanctum," one of Bloomberg's senior commissioners explained. It was supposed to evoke open and egalitarian cooperation, but seemed to result in unwanted noise and confusion at least as much as transparency or openness.

Shortly after Bloomberg's idea was put into reality, Washington, D.C., Mayor Adrian Fenty made a similar move, eliminating his predecessor's private suite, as Governing's Christopher Swope wrote, for an open-air cubicle set down "amongst the managerial masses."

Public schools throughout the country experimented with the practice of tearing down classroom walls, turning their entire classroom space into an undifferentiated piece of territory in which each cluster of pupils could stare at the others. It was never entirely clear what the open-classroom movement was supposed to accomplish, and many school boards eventually became disillusioned with it, but its ideology and its physical remnants still have not disappeared from the scene decades later.

The cult of opening things up went far beyond its physical manifestations. It's a bit startling in 2020 to reflect on how many important public decisions a half-century ago were made in private, behind invisible barriers. Crucial public votes in the U.S. House of Representatives were not traceable to the individuals who cast them. State legislative bodies met and made decisions behind closed doors. City managers in much of the country disposed of major public questions over coffee with senior business moguls in the morning at local cafés.

Today, virtually everywhere in America, all of this is ancient history. On a five-member local council, for example, it is frequently illegal for even three of the members to meet together without inviting the public. So much that was tightly held a generation ago is now wide open for inspection.

BUT IT WOULD BE MISLEADING to summarize the opening of American structures and institutions without taking note of the contradictory strands of public life that were moving in the opposite direction at the same time. The 1970s were the heyday of the "defensible-space" movement, which recommended that urban neighborhoods could be made safer by erecting traffic barriers that kept outsiders, many presumed to be criminals, from coming inside. The 1990s were the peak moment for gated communities, the suburban enclaves with iron gates and uniformed guards to prevent the entry of anyone who did not live there and had not been invited in. Many Americans sent their children to open-plan schools and celebrated open government while living in neighborhoods that were to all practical purposes closed.

By 1997, there were an estimated 20,000 gated communities in the United States. Approximately 40 percent of new developments in California were said to be behind walls. One guess was that there were between 4 million and 8 million Americans living in gated developments as the new century began. Since then, reliable studies have concluded that these developments were no safer than conventional neighborhoods, and the enthusiasm for them has begun to wane, at least in the United States. They are as tangible a reminder of the modern open versus closed contradiction in modern public life as the sprawling public atrium or the classroom without walls.

But the most glaring contradiction on the openness question in the last couple of decades has been our attitude toward the Internet and the privacy questions it inevitably poses. We launch federal investigations into the release by social media of personal information that we don't want to make available to the general public. At the same time, we launch endless revelations about each other onto wide-open social-media sites without even stopping to consider whether they might best be kept to ourselves. It is an age of broadcasting sensitive information to the entire world; it is also an age of obsessive concern about personal details leaking into the wrong hands.

As conflicting as the evidence may seem, there is little doubt that we have been passing through a period when tearing down walls, physically and metaphorically, was more central to our societal values that creating new ones. The question, as you have probably guessed by now, is whether that balance is about to shift. Even before this year, Amanda Mull writes, the demand for open-plan offices was shrinking, and the demand for conventional layouts with private offices was on the increase. Similarly, real-estate professionals report that buyer interest in open-plan houses is lower than in the recent past, with demand for more traditional designs trending higher. And there are plans to surround the South Dakota governor's mansion, long wide open to the community, with a protective fence.

Now, of course, we are facing a brand-new circumstance generated by the coronavirus, one that seems to be opening things up and keeping us apart at the same time. We have the opportunity to dine outside in the open air, in the middle of the street, something few of us had before. On the other hand, we are not supposed to come within six feet of one another, creating a new form of invisible wall that may (or may not) reach further into the months and years ahead. That invisible wall could extend to other forms of in-person sociability that COVID-19 has discouraged and that the post-virus environment might perpetuate. All of this reinforces the open versus closed duality that we have been living with as far back as any of us can remember.

We may be entering upon a new acceptance of separation and enhanced privacy, and that is not necessarily a terrible thing. Still, it is worth recalling some other lines from Frost's poem: "Before I built a wall I'd ask to know/What I was walling in or walling out,/And to whom I was like to give offense."