In pre-industrial societies, common land between houses and between workshops existed automatically - so it was never necessary to make a point of it. The paths and streets which gave access to buildings were safe, social spaces, and therefore functioned automatically as common land.
But in a society with cars and trucks, the common land which can play an effective social role in knitting people together no longer happens automatically. Those streets which carry cars and trucks at more than crawling speeds, definitely do not function as common land; and many buildings find themselves entirely isolated from the social fabric because they are not joined to one another by land they hold in common. In such a situation common land must be provided, separately, and with deliberation, as a social necessity, as vital as the streets.
The common land has two specific social functions. First, the land makes it possible for people to feel comfortable outside their buildings and their private territory, and therefore allows them to feel connected to the larger social system - though not necessarily to any specific neighbor. And second, common land acts as a meeting place for people.
The first function is subtle. Certainly one's immediate neighbors are less important in modern society than in traditional society. This is because people meet friends at work, at school, at meetings of interest groups and therefore no longer rely exclusively on neighbors for friendship. (See for instance, Melvin Webber, "Order in Diversity: Community Without Propinquity," Cities and Space,ed. Lowdon Wingo, Baltimore: Resources for the Future, 1963; and Webber, "The Urban Place and the Nonplace Urban Realm," in Webber et al., Explorations into Urban Structure,Philadelphia, 1964, pp. 79-153.)
To the extent that this is true, the common land between houses might be less important than it used to be as a meeting ground for friendship. But the common land between buildings may have a deeper psychological function, which remains important, even when people have no relation to their neighbors. In order to portray this function, imagine that your house is separated from the city by a gaping chasm, and that you have to pass across this chasm every time you leave your house, or enter it. The house would be disturbingly isolated; and you, in the house, would be isolated from society, merely by this physical fact. In psychological terms, we believe that a building without common land in front of it is as isolated from society as if it had just such a chasm there.
There is a new emotional disorder - a type of agoraphobia making its appearance in today's cities. Victims of this disorder are afraid to go out of their houses for any reason - even to mail a letter or to go to the corner grocery store - literally, they are afraid of the marketplace - the agora. We speculate - entirely without evidence - that this disorder may be reinforced by the absence of common land, by an environment in which people feel they have no "right" to be outside their own front doors. If this is so, agoraphobia would be the most concrete manifestation of the breakdown of common land.
The second social function of common land is straightforward. Common land provides a meeting ground for the fluid, common activities that a house cluster shares. The larger pieces of public land which serve neighborhoods - the parks, the community facilities - do not fill the bill. They are fine for the neighborhood as a whole. But they do not provide a base for the functions that are common to a cluster of households.
Lewis Mumford:
How much common land must there be? There must be enough to be useful, to contain children's games and small gatherings. And enough land must be common so that private land doesn't dominate it psychologically. We guess that the amount of common land needed in a neighborhood is on the order of 25 per cent of the land held privately. This is the figure that the greenbelt planners typically devoted to their commons and greens. (See Clarence Stein, Toward New Towns in America,Cambridge: M.I.T. Press, 1966.)
With cooperation among the people, it is possible to build this pattern piecemeal, into our existing neighborhoods by closing streets.
