Jane Jacobs, the legendary urbanist, gifted the city her commonsense observations of what makes for flourishing community. While she walked her beloved Greenwich Village, she’d watch the comings and goings of a city alive with humanity.  Her streets had soul. But, Jacobs wondered, why did other neighborhoods seem so lifeless? It soon became her life’s work to figure these things out, and in time her writings inspired a similar eye for the city among others.

Her most famous book, “The Death and Life of Great American Cities,” is full of insightful observations about everything from parks to street corner bodegas—as well as fire-breathing bromides against the developers of her era. She rewards the close reader with witty counsel that seems as relevant today as it did in the middle of the last century. Yet step back from the pages of her book and even more timeless truths emerge.

One of Jacobs’ lessons to city leaders was that they knew less than they thought they knew. Human beings are complex creatures as are their societies. The fatal conceit of city planners in her era was their modernist notion of man triumphing over nature.

“Leaders should plan for the city as an open-ended, complex system.”

Jacobs would recount leaders turning up their noses at diverse and vibrant neighborhoods, like Boston’s North End, because they didn’t fit their uniform plans. Their plans, after all, had been incubated by the finest minds of MIT and Harvard, and laid out with an elegance befitting their credentials. Jacobs realized that city leaders needed to put people first rather than obsessing over place, and doing so well meant recognizing the imperfect nature of their centralized planning.

Cities are simply dense networks of interwoven relationships. They are decentralized but organized. The more complex the networks, the more prosperous the city. Put another way, a city is the original social network.

City leaders are easy to spot; that’s where these human links cluster together into little nodes. They are usually a hundred or so people in a city a thousand times their size. Jacobs called them “hop-skip people” who provided “bridging social capital.”

“It takes surprisingly few hop-skip people,” Jacobs said, “relative to a whole population, to weld a district into a real thing. […] Once a good, strong network of these hop-skip links does get going in the city district, the net can enlarge relatively swiftly and we’ve created all kinds of resilient new patterns.”

Networks are what make effective governance and a thriving civic life possible.

If self-government in the place is to work, underlying any float of population must be a continuity of people who have forged neighborhood networks. These networks are a city’s irreplaceable social capital. Whenever the capital is lost, from whatever cause, the income from it disappears, never to return until and unless new capital is slowly and chancily accumulated.

Cities are dynamic organisms. To flourish, they must remain open to people coming and going, and boast a diversity of uses beyond any original intent. Top-down direction is unlikely to work; self-organization, even with its seeming chaos, is the best course of action for a thriving city. “A city’s collection of opportunities of all kinds,” as Jacobs says, “and the fluidity with which these opportunities and choices can be used, is an asset—not a detriment—for encouraging city-neighborhood stability.”

Space, time, and infrastructure enable social networks to form and grow. Leaders should plan for the city as an open-ended, complex system. The aim should be, as Patrick Geddes once said, “To undo as little as possible, while planning to increase the well-being of the people at all levels, from the humblest to the highest.”

Cities succeed only by making the most of their assets. And their greatest asset is their people, unfettered and free.