Cities have been getting a good press in recent years.
This is quite a turn round, since for a century and a half it has been widely believed (with exceptions that are too familiar to mention) that large dense aggregations of people were so unlike the ways in which societies had previously been organised in space, that they were likely to be in themselves socially negative. Now cities are more and more seen as positive, largely because the very factors of scale and density which had been associated with social disorder and malaise, are now seen as sources of economic and intellectual creativity. It is easy to ﬁnd statistical evidence in support of both sets of beliefs – higher rates of crime and social malaise on the one hand and higher innovation and economic performance on the other – but little hardedged explanation of exactly how either type of outcome might arise from the fact of cities.
Against this background, the aims of this paper are three-fold. First, to conﬁrm through real cases that in cities, as in any science, statistical associations tell us little without an account of credible and testable mechanisms by which one factor can create effects in another. We give examples to illustrate this. Second, we show mechanisms that link street conﬁguration in cities to all three commonly argued components of sustainability, the environmental, the economic and the social, and on this basis argue that there is such a thing as spatial sustainability in cities. Finally, we argue that there is a fourth component of spatial sustainability, no less important in the long run than the other three: creativity, and we conjecture mechanisms by which the fact of cities can be linked credibly to this fourth dimension of sustainability.