Cities are often seen as symbols of order: the existence of city

walls, fortified gates, palaces, temples, roads, pavements, highways,

public institutions, city centres and residential areas is interpreted

as indicating the existence of a central authority that plans

and controls the city. On the other hand, the very same cities are

also seen as symbols of spontaneous growth. The little winding

streets and alleys, the mixture of physical structures, styles and

human activities have often given the impression that cities, like

forests, and other natural entities are organic structures - strange

'natural artifacts'.

Tokyo is a good example for this dual nature of cities. When you

first encounter it, you get the impression of chaos: old buildings

with one or two storeys next to 30-, 40- or 50-storey skyscrapers;

pedestrians, cars, trains moving in all directions, each with its own

trajectory. But then you realize that this seemingly chaotic structure

provides a context for perfectly ordered human activities: trains

leave and arrive as timetabled, their doors open at the exact points

that are marked with yellow lines on the platforms; early in the

morning fishermen bring their catch to Tokyo's big fish market, auctions

are held, and by six o'clock this huge amount of sea food has

already been distributed among thousands of restaurants all over

the city. And if you look deeper you learn that the chaotic face of

Tokyo is the precondition for its ordered and organized life.

Complexity theory or self-organization theory are umbrella terms

for a set of theories that study the interplay between chaos and

order. Originating in the sciences, these theories have been applied

to the study of cities in the last three decades. They show that as

in natural systems, in the artificial systems that we call cities, chaos

and order do not stand in opposition to each other. Rather, they

coexist in an ongoing interplay of circular causality: chaos is the precondition

for new urban orders to emerge and then to reproduce

themselves, whereas order and organization set the boundaries

within which chaotic structures and behaviors can take place.

Juval Portugali is professor of human geography in the Department

of Geography and the Human Environment at Tel Aviv University.

His research is devoted to the city as a self-organizing system.

In addition to his teaching in Israel, he has taught at many universities

outside his home country as a guest professor, including Tokyo

University. Wolf-Dieter Gericke studied architecture at Stuttgart University.

He works as a free-lance photographer and designer in

Waiblingen near Stuttgart. He has been visiting Tokyo almost every

year for some time now.