The notion of the rural-urban continuum evolved from the work of Louis Wirth (1938) on the social distinctiveness of the city.
Societies at the rural end of the continuum are envisaged as being close knit, rigidly stratified, highly stable, integrating and homogeneous in composition. Urban societies are supposed to be loose in association, unstable in membership, characterized by great social mobility and with a tendency for inter-individual contacts to occur only in one situational context (e.g., workplace, kinship, recreation) whereas in rural societies contact would occur in several different contexts. The continuum has been seen both as a classificatory device and as marking a process of social change. The view of the continuum as marking a process is criticized and discredited by the fact that social change can occur without any growth of settlement or increase in population, e.g., through the replacement of an original rural population by commuters.
More serious is the criticism that it is possible to find rural societies in urban settings, and urban societies in villages. The association between settlement size and societal type is thus shown not to be perfect, although the continuum concept may still have some general validity. Alternatives have been suggested to the rural-urban continuum as the most useful description of ways of life.
The most interesting is the idea put forward by R.E. Pahl (1966) that within any area of population there are likely to be both nationally and locally oriented individuals and groups, with the balance varying from place to place.
Such a framework facilitates the study of the effect of national developments on local social systems, as occurred in dormitory villages and with tourism. The rural-urban continuum has been supported by studies showing the existence of rural-urban differences in such things as religious and political attitudes, the incidence of fertility control and social behaviour. Such studies, however, confirm only a modified view of the continuum, the controlling factor on the society often being the distance from urban centres of social diffusion, or some aspect of occupation distinctiveness, rather than settlement type as in the original settlement of the concept. The settlements in which most of the people are engaged in secondary, tertiary and quaternary activities are known as urban places. In other words, urban relates to cities and towns.
If urbanization is regarded as a demographic process only, then urban places are those which exceed a population size and/or density threshold. Size, density and occupations are the criteria frequently used in census and other definitions of urban places, though the particular division between urban and rural is arbitrary. The study of urban places has been central to several social sciences, including geography because of their importance in the distribution of population and in the organization of production, distribution and exchange.