After finishing Robert Caro’s The Power Broker: Robert Moses and the Fall of New York, I decided I had to read The Death and Life of Great American Cities, the great response by Jane Jacobs to all the excesses of central planners and the cult of the expert.

I’ve just finished it. It was surprising how heavily she leans on Philadelphia in addition to New York and Boston to cite examples of good and bad city life. I had imagined it was exclusively New York-focused, for whatever reason.

In this excerpt, Jacobs outlines the “four conditions” that guide her analysis of good city life:

So long as we are content to believe that city diversity represents accident and chaos, of course its erratic generation appears to represent a mystery.

However, the conditions that generate city diversity are quite easy to discover by observing place in which diversity flourishes and studying the economic reason why it can flourish in these places. Although the results are intricate, and the ingredients producing them may vary enormously, this complexity is based on tangible economic relationships which, in principle, are much simpler than the intricate urban mixtures they make possible.

To generate exuberant diversity in a city’s streets and districts, four conditions are indispensable:

1. The district [neighborhood], and indeed as many of its internet parts as possible, must serve more than one primary function; preferably more than two. These must insure the presence of people who go outdoors on different schedules and are in the place for different purposes, but who are able to use many facilities in common.
2. Most blocks must be short; that is, streets and opportunities to turn corners must be frequent.
3. The district must mingle buildings that vary in age and condition, including a good proportion of old ones so that they vary in the economic yield they must produce. This mingling must be fairly close-grained.
4. There must be a sufficiently dense concentration of people, for whatever purposes they may be there. This includes dense concentration in the case of people who are there because of residence.

The necessity for these four conditions is the most important point this book has to make. In combination, these conditions create effective economic pools of use. Given these four conditions, not all city districts will produce a diversity equivalent to one another. The potentials of different districts differ for many reasons; but, given the development of these four conditions (or the best approximation to their full development that can be managed in real life), a city district should be able to realize its best potential, wherever that may lie. Obstacles to doing so will have been removed. The range may not stretch to African sculpture or schools of drama or Rumanian tea houses, but such as the possibilities are, whether for grocery stores, pottery schools, movies, candy stores, florists, art shows, immigrants’ clubs, hardware stores, eating places, or whatever, they will get their best chance. And along with them, city life will get its best chances.