Cities are obvious metaphors for life. We call roads arteries and so forth.

Cities tolerate crazy people. Companies don't.

One of the remarkable things about slums is that they do develop their own social organization and economy and even culture that is, on some level, functional and in some cases, remarkably resilient. This is kind of amazing.

You could not have evolved a complex system like a city or an organism - with an enormous number of components - without the emergence of laws that constrain their behavior in order for them to be resilient.

When people come together, they become much more productive.

The paradigm of physics - with its interplay of data, theory and prediction - is the most powerful in science.

Cities are the crucible of civilization.