Whilst there seems to be a consensus on the feasibility of applying sustainability thinking to town and city development, our research contributes to the critical understanding of the notion of a sustainable city within the field of urban planning. We will begin with a study of the modalities of the emergence of this term, combining it with an analysis of the ways in which the notion is used in professional and scientific literature. Following on from the correspondence drawn between "méditerranéité" and complex thinking (MORIN 1999), our approach will then be embodied in the heart of a Mediterranean city : Marseille. Considering the mental pictures conjured up by the notion of sustainable city, we thus analyse the ways in which the elements of meaning previously highlighted are being used or not, interpreted, or even diverted, and how they influence decisions and actions. As the object of our work is the relationship between these and their material, socio-spatial and experiential impact, we then go on to conduct a sensitive exploration using observations and stories told by local residents within a sector in which actualisation principles are relating to the idea of sustainable city. This research shows, in the end, how the notion of sustainable city, which is exogenous to the domain of urban planning, does not offer a sufficiently emancipating or robust framework to allow the development of new "knowledge and know-how" or to outweigh the constraints and forceful trends that hinder the development of the town. This leads us to propose an "ecological" approach to explore what and whose contributions urban sustainability or rather sustainabilities might be built upon.
