With the publication of The Image of the City, Kevin Lynch embarked on the process of exploration of city form. A Theory of Good City Form, his most important book, is both a summation and an extension of his vision, a high point from which he views cities past and possible.

The central section of the book develops a new normative theory of city form—an identification of the characteristics that good human settlements should possess. This follows an examination of three existing normative theories—those which see the city as a model of the cosmos, as a machine, and as a living organism—which are shown to be finally inadequate and unable to hold up under sustained analysis. In addition, an appendix demonstrates the inadequacies of a number of functional theories—those whose aim is simply to describe how settlements work rather than to evaluate how they ought to work. Among these theories are models of cities as ecological systems, as fields of force, as systems of linked decisions, or as areas of class conflict.

Lynch puts forth his own theory by searching out the qualities that produce good settlements, qualities that allow development, within continuity, via openness and connection.” He identifies five interrelated dimensions of performance—vitality