Our communities have grown blindly, and, escaping the natural limitations which curbed even the Roman engineers, have not been controlled, on the other hand, by any normative ideal. One step in the direction of departing from our pioneer customs and habits would be to consider what the nature of a city is, and what functions it performs. The dominant, abstract culture of the nineteenth century was blithely unconcerned with these questions, but, as I have already pointed out, the Puritans not merely recognized their importance, but regulated the plan and layout of the city accordingly. The notion that there is anything arbitrary in imposing a limitation upon the area and population of a city is absurd: the limits have already been laid down in the physical conditions of human nature, as Mr. Frederic Harrison once wisely observed, in the fact that men do not walk comfortably faster than three miles an hour, nor can they spend on the physical exertion of locomotion and exercise more than a few hours in every twenty-four. With respect to the needs of recreation, home-life, and health, the growth of a city to the point where the outlying citizen must travel two hours a day in the subway between his office and his place of work is unintelligent and arbitrary. A city, properly speaking, does not exist by the accretion of houses, but by the association of human beings. When the accretion of houses reaches such a point of congestion or expansion that human association becomes difficult, the place ceases to be a city. The institutions that make up the city--schools, clubs, libraries, gymnasia, theaters, churches, and so forth--can be traced in one form or another back to the primitive community: they function on the basis of immediate intercourse, and they can serve through their individual units only a limited number of people. Should the population of a local community be doubled, all its civic equipment must be doubled too; otherwise the life that functions through these institutions and opportunities will lapse and disappear. It is not my purpose to discuss in detail the various devices by which our practice of endless growth and unlimited increment may be limited. Once the necessary conversion in faith and morals has taken place, the other things will come easily: for example, the social appropriation of unearned land-increments, and the exercise of the town-planner’s art to limit the tendency of a community to straggle beyond its boundaries.