There is a fantastic word in German: Aufheben. How this word captures the essence of dialectical social space was discovered by Schmid (2007), and his observation is worth repeating here:At the core of the dialectic lies a concept whose deeper meaning emerges only in German: das Aufheben des Widerspruchs (sublation of the contradiction). Aufheben signifies, on the one hand, negation and overcoming: on the other hand, preservation and placing at a higher level. This ambiguity is completely lost in most translations: for example, in the French (dépasser) or English ("transcend" or "sublate") (Schmid, 2007, p. 30) Further contradictory translations include to dissolve, to keep, to remove, to raise, to void, and to sustain. In this way, Aufheben captures the core contradictions of social space that define social reality (Schmid, 2007). It is exactly this dialectic that surfaces time and again at the interface between sustainable development policy and planning practice, and this is the central theme of this issue of the Interface. On the one hand, sustainable development signifies the normative ideal of generating a better world. On the other, in the process of addressing and resolving problems it often results in the realisation of other problems, if not also the preservation of current problems (e.g. capitalist relations). This contradiction is an unfortunate, if not depressing, observation given that over 25 years have passed since the World Commission on Environment and Development's (1987) declaration that sustainable development is a goal worthy of international attention. Recalling further Jordan's (2008, p. 17) remark that, "things have gotten worse -not better -since the publication of Brundtland's landmark report", one might wonder how progress will ever be achieved, given the numerous attempts that have been made so far at realising it.Across the wide palette of such attempts, one can see that the urban has surfaced as "the" site of sustainability interventions. Rydin (2010) cited several reasons for this. First, the idea that the planet's population is more than half urbanised renders urban places increasingly important nodes of human affairs and therefore logical starting points to intervene and invoke wide-reaching change. By extension, second, the reshaping of cities and neighbourhoods (through, for example, new infrastructure) can potentially generate new and sustainable ways of living. Third, negotiations over land use, building codes, and/or zoning, often unfold at the municipal level. Forums of local decision-makers are, therefore, logical venues to thematise and, hopefully, materialise sustainable development ideals. This consensus that the urban is the site of mediation has, in many places, been translated into a call to the planning profession to produce the twenty-first-century sustainable city, and one can observe a vast array of designs, approaches, and indeed, entire planning paradigms such as integrative spatial planning, which have emerged as tools to address this normative orientation....