Cities never flourish alone. They have to be trading with other cities. My new hypothesis shows why. But also in trading with each other they can't be in too different stages of development, and they can't copy one another.

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.

When we deal with cities we are dealing with life at its most complex and intense. Planners are guided by principles derived from the behaviour and appearance of suburbs, tuberculosis sanatoria, fairs and imaginary dream cities - from anything but cities themselves.

observation of realities has never, to put it mildly, been one of the strengths of economic development theory.

Cities need old buildings so badly it is probably impossible for vigorous streets and districts to grow without them.... for really new ideas of any kind--no matter how ultimately profitable or otherwise successful some of them might prove to be--there is no leeway for such chancy trial, error and experimentation in the high-overhead economy of new construction. Old ideas can sometimes use new buildings. New ideas must use old buildings.

Old ideas can sometimes use new buildings. New ideas must use old buildings.

(The psuedoscience of planning seems almost neurotic in its determination to imitate empiric failure and ignore empiric success.)