Henri Lefebvre gave suggestive hints at a theory of urban form that have inspired those involved in the design and planning disciplines. His search was for an urban praxis that opened potentials for new forms of social relations and to this end he proposed a "metaphilosophy" designed to engage with the open-ended material relations of cities and societies. This, however, contradicted his Marxist commitment to a "finality" of man and society and his association of technology with alienation. We try here to rethink technology as intrinsic to human and social life: not as means to realize thought in the materialization of spaces and societies, but as medium and source, in processes of historical realization, of orders that come before thought in human practice. We relate this to "worlds" of practice which are the technically and historically constructed "metaphilosophical" "totalities" within which we are enabled and act. This pluralizes and technologizes "world," and Lefebvre’s "urban form" becomes a construction of multiple relational–technological "worlds," each perceived, conceived, and lived as wholes. These articulate with one another and evolve historically. It is the articulations and interfaces between "worlds" rather than the "worlds" themselves which locate the places of productivity and vitality in the city. The question of an open urban shifts subtly from one of resistance to the abstract rationalities of "planning" or an "authoritarian state" to one of the maintenance of open relations between different "worlds" each with their necessary technical or abstract rationalities.