She describes a trip to Boston's North End neighborhood in 1959, finding it friendly, safe, vibrant and healthy, and contrasting her experience against her conversations with elite planners and financiers in the area, who lament it as a "terrible slum" in need of renewal.

Branding the mainstream theory of cities as an "elaborately learned superstition" that had now penetrated the thinking of planners, bureaucrats, and bankers in equal measure, she briefly traces the origins of this "orthodox urbanism."

Garden City was conceived as a new master-planned form, a self-sufficient town removed from the noise and squalor of late 19th century London, ringed by agriculture green belts, with schools and housing surrounding a highly prescribed commercial center.

The Garden City would allow a maximum of 30,000 residents in each town, and called for a permanent public authority to carefully regulate land use and ward off the temptation to increase commercial activity or population density.

The Decentrists proposed to use regional planning as a means to ameliorate the woes of congested cities, attracting residents to a new life in lower-density fringes and suburbs and thereby thinning out the crowded urban core.

Jacobs highlights the anti-urban biases of the Garden City advocates and the Decentrists, especially their shared intuitions that communities should be self-contained units; that commingled land use created a chaotic, unpredictable, and negative environment; that the street was a bad locus for human interactions; that houses should be turned away from the street toward sheltered green spaces; that super-blocks fed by arterial roads were superior to small blocks with overlapping cross-roads; that any significant details should be dictated by permanent plan rather than shaped by organic dynamism; and that population density should be discouraged, or at least disguised to create a sense of isolation.

Jacobs continues her survey of orthodox urbanism with Le Corbusier, whose Radiant City concept envisioned twenty-four towering skyscrapers within a Great Park.

Jacobs concludes her introduction with a reference to the City Beautiful movement, which dotted downtown areas with civic centers, baroque boulevards, and new monument parks.

These efforts borrowed concepts from other contexts, such as single-use public space disconnected from natural walking routes and the imitation of the exposition grounds at the World's Fair in Chicago.

Jacobs admits that the ideas of the Garden City and the Decentrists made sense on their own terms: a suburban town appealing to privacy-oriented, automobile-loving personalities should tout its green space and low-density housing.

Jacobs' anti-orthodox frustration stems from the fact that their anti-urban biases somehow became an inextricable part of the mainstream academic and political consensus on how to design cities themselves, enshrined in course curricula and federal and state legislation affecting, inter alia, housing, mortgage financing, urban renewal, and zoning decisions.

"This is the most amazing event in the whole sorry tale: that finally people who sincerely wanted to strengthen great cities should adopt recipes frankly devised for undermining their economies and killing them."

Jacobs claims that a Brooklyn project successfully reduced vandalism and theft by opening the corridors to public view, equipping them as play spaces and narrow porches, and even letting tenants use them as picnic grounds.

Building on the idea that a bustling pedestrian environment is a prerequisite for city safety in the absence of a contracted surveillance force, Jacobs recommends a substantial quantity of stores, bars, restaurants, and other public places "sprinkled along the sidewalks" as a means to this end.

She argues that if city planners persist in ignoring sidewalk life, residents will resort to three coping mechanisms as the streets turn deserted and unsafe: 1) move out of the neighborhood, allowing the danger to persist for those too poor to move anywhere else, 2) retreat to the automobile, interacting with the city only as a motorist and never on foot, or 3) cultivate a sense of neighborhood "Turf", cordoning off upscale developments from unsavory surroundings using cyclone fences and patrolmen.

Residents in places with no sidewalk life are conditioned to avoid basic interactions with strangers, especially those of a different income, race, or educational background, to the extent that they cannot imagine having a deep personal relationship with others so unlike themselves.

Over countless minor interactions, children absorb the fact that the sidewalk's natural proprietors are invested in their safety and well-being, even lacking ties of kinship, close friendship, or formal responsibility.

Jacobs states that sidewalks of thirty to thirty-five feet in width are ideal, capable of accommodating any demands for general play, trees to shade the activity, pedestrian circulation, adult public life, and even loitering.

Jacobs offers four tenets of good park design: intricacy (stimulating a variety of uses and repeat users), centering (a main crossroads, pausing point, or climax), access to sunlight, and enclosure (the presence of buildings and a diversity of surroundings).

But with so many worthy urban investments going unfunded, Jacobs warns against "frittering away money on parks, playgrounds and project land uses too large, too frequent, too perfunctory, too ill-located, and hence too dull or too inconvenient to be used."

Jacobs ultimately defines neighborhood quality as a function of how well it can govern and protect itself over time, employing a combination of residential cooperation, political clout, and financial vitality.