Informal housing, often dismissed as slums or squatter settlements, constitutes a major part of the housing in developing Third World countries. Many researchers attribute the emergence and development of such informal housing, or what some call "bottom-up urbanization," to the informal and uncontrolled economy in countries of the Global South. Several theories emerged in the mid-twentieth century to explain this phenomenon, which led to proposals and policies that encouraged the urban poor to build their own homes. However, this idea met with limited success. This study, which presents a critique of some of these proposals and policies, offers a new theoretical contribution to the understanding of bottom-up urbanization with an emphasis on the centrality of the cultural factor.