In trading with each other cities can't be in too different stages of development, and they can't copy one another. Backward cities, or younger cities, or newly forming cities in supply regions, have to develop to a great extent on one another's shoulders. This is one of the terrible things about empires. Empires want them only to trade with the empire, which doesn't help them at all. It's just a way of exploiting them.

A border--the perimeter of a single massive or stretched-out use of territory--forms the edge of an area of 'ordinary' city. Often borders are thought of as passive objects, or matter-of-factly just as edges. However, a border exerts an active influence.

There are two ways you encounter things in the world that are different. One is everything that comes in reinforces what you already believe and everything that you know. The other thing is that you stay flexible enough or curious enough and maybe unsure of yourself enough, or may be you are more sure of yourself - I don't know which it is - that the new things that come in keep reforming your world view.

The entrepreneurial investors of the time just want to repeat themselves indefinitely and don't know when to stop. You can't do that. And so finally the housing boom, or the auto boom, or whatever it is that's been carrying things along, runs out of customers.

A region is an area safely larger than the last one to whose problems we found no solution.

It may be that we have become so feckless as a people that we no longer care how things do work, but only what kind of quick, easy outer impression they give. If so, there is little hope for our cities or probably for much else in our society. But I do not think this is so.

The ballet of the good city sidewalk never repeats itself from place to place, and in any one place is always replete with new improvisations.