The need for theory and for a historical perspective in attempting to arrive at a valid theory are widely recognized among sociologists, but preconceived notions of a systemic nature would seem to be standing in the way of an unbiased evaluation of the data of history. The paper analyzes the work of two leading urban sociologists who assume that preindustrial and industrial cities represent closed and mutually exclusive systems. Consequently, they assemble sustaining data, but brush aside contrary evidence which would tend to establish the city as a phenomenon in its own right, and the modern city as antedating industrialization. In historical view, the city appears as an emergent rather than as a variable, both in ancient Babylonia and in medieval Europe. The present-day city, ecologically enlarged into “urban regions,” sociologically provides the principle for the organization of the total society, but the twofold model of the ancient and the medieval city, if understood ideal-typically, remains serviceable as an analytical tool.