One source of several of Postrel's examples is a book by Stewart Brand, the author of 1970's "The Whole Earth Catalog." In the mid-1990s, Brand wrote "How Buildings Learn," which Postrel uses as a metaphor for dynamism. His idea is that over time, buildings inevitably change because the people who inhabit them either as homes or as workplaces have needs that lead them to adapt their buildings. "And the good buildings, in his mind," Postrel says, "are those that are more adaptable, that allow you to change them over time. That they aren't so rigidly laid out or constructed that they can't be changed. So that for example, he points out, that people immediately start fooling with their garages or their attics or anything that's kind of extra space."

Brand makes the point that architects often are rewarded for making buildings that look good in still photographs. Postrel says that this very different from "buildings that are good for people to live or work in, over time, which is an ongoing dynamic process. I don't agree with everything in the book, but it's a very good case study or application in one little area of the world of some of these principles. He talks about how in a building you have different layers, if you will, that get more and more easily adaptable the further in you go. So it's really easy to move the furniture. It's a little more difficult to move a wall. It's a little bit more difficult still, to change the ductwork or the plumbing and ultimately, it's very difficult to change the site. I think there's six or seven layers.

"It's a very good model of how rules can go together in a dynamic system. And I think it's just an interesting meditation on adaptability over time, which is really what dynamism is about."

On the Verge

Outside of our home, Postrel is particularly fond of what she calls "third places" (an idea which Postrel says grew out of a book by Ray Oldenburg) as dynamic spaces where we can interact, freed from the rigid spaces of our home or office.

Third places are places "on the verge." They're not home, but they're not just retail establishments. Places like Internet cafes aren't just places to buy coffee and browse the Web, they're a place to meet friends and communicate new ideas in a dynamic setting. Rigid categories like gathering place, retail business and social club often blend together in today's society. In "The Future and Its Enemies," Postrel sees society as a whole as being on the verge. In fact, in her last chapter, she talks extensively of verges.