We are all Jane Jacobsites today. To oppose her vision of the world, the subject of a small but informative new exhibition at the Urban Center, is tantamount to opposing trees and children. Now some people do oppose trees and children, but they don’t come right out and say such things, assuming that they have or hope to have any access to power in their communities. Obviously many people take Jane Jacobs’s name in vain, and many on either side of the urban debate claim her for their own. But the important thing is that — with the exception of a few younger urbanists rebelling against their parents — her vision of the world has overwhelmingly won the day.

Jane Jacobs was an inhabitant of Greenwich Village during its days of beatnik glory. For 20 years, she lived above a candy store at 555 Hudson St., in a house that became something of a shrine. It was from these steps and on these sidewalks that, legend has it, she watched the world go by, in the process synthesizing observations that would change the nature of urban planning and even of the individual’s interaction with the larger forces of municipal government. What she came to appreciate is what she called the ballet of the sidewalk, the complex patterns of interaction among people of different ages and careers along that sliver of the public realm that separates the buildings from the road. “Something is always going on,” she wrote of an effective cityscape. “The ballet is never at a halt.”

Like most of the shows mounted by the Municipal Arts Society — indeed, like most architectural exhibitions in general — “Jane Jacobs and the Future of New York” is largely an affair of texts mounted on panels. But the present show, more than most, is enlivened by a video loop of the street right outside the window at Madison Avenue and 51st Street, presented over a 24-hour period in time-lapse photography. Also on view is a municipal model of a major highway that was intended to cut through the heart of SoHo, as well as fan letters from the like of Lewis Mumford and one stunningly brief and snotty letter from Jacobs’s nemesis Robert Moses to Bennett Cerf, who edited Jacobs’s book “The Death and Life of Great American Cities.” The note obliquely threatens legal action and dismisses the book as “junk.”

This exhibition poses a question that it does not attempt to answer: What would Jane Jacobs say about contemporary New York? The point of the question, like the point of Jacobs’s entire career, is to cause viewers to see their surroundings not as something fixed and immutable, almost a natural occurrence, but as something created by man, for better or for worse. Of course it could be argued that no one who goes to see a show at the Municipal Arts Society is likely to need such an injunction to reflect on urbanism. But the public does need to learn this lesson, to understand how every decision that a city makes with regard to its appearance, its traffic flow, the length of its blocks, and the intervals of parkland will have far-reaching consequences for generations to come.

The show focuses on four main aspects of Jacobs’s advocacy: mixed uses of the buildings in a neighborhood, so that it will remain vibrant with different activities at different times of the day; varied buildings, as an antidote to the modernist monoliths that, especially in the postwar era, were devouring New York; short blocks that make more of the city available to sidewalks, unlike the superblocks favored by modernist city planners, and finally concentration, that is, urban density as opposed to the lofty, tower-in-thepark ideals of Le Corbusier and an entire generation of his followers. All of which bring us back to the central question of the exhibition: What would Jane Jacobs think of New York today? In theory, we are somewhat closer to what she prescribed than we were nearly 50 years ago. There is, if nothing else, an appreciation of neighborhoods as opposed to impersonal building complexes, and she would doubtless be gratified that in places such as Harlem, where there was considerable slum clearance, a number of recent projects have re-introduce the scale and the feel of the row houses that were bulldozed away in the 1950s and 1960s.

Varied buildings have also carried the day, as can be seen along 125th Street as well as along 42nd Street. These same stretches have been provided with mixed-use buildings, so that they remain vibrant throughout the day and night.

Even in the matter of shorter blocks, which are the hardest thing to change in a city’s makeup, progress has been made. The World Trade Center site was a perfect example of the modernist super-block, anaggregateofsmaller blocks that it had eaten up. When the site is renovated, several years hence, some of the smaller blocks that had been subsumed in the larger project will be restored, in large measure because of what Jane Jacobs observed along Hudson Street half a century ago.

Until January 5 (457 Madison Ave., between 50th and 51st streets, 212-935-3960).