“…In providing answers to these questions, the concept of sustainable development, including its utopian character, must be seriously considered, and an interdisciplinary approach to addressing the object itself must be developed (Mathieu, 2006). This also involves thinking about the way interdisciplinarity can be geared towards both the requirements of public action and the needs of modern societies, which more fundamentally raises questions about the relation between research and action and about the way to redefine the science and society relationship (Gauthier, 2006). The papers assembled in this special issue devoted to the topic of "urban planning and sustainable development" are in keeping with the view that the concepts of "sustainable city" and of "urban sustainable development" are to be seriously considered from a wide range of theoretical, conceptual and methodological perspectives.…”