Why is it so difficult to define concisely the meaning of 'planning' and many of its dominant concepts-public interest, new urbanism, sustainability or smart growth-when deployed in formulating urban policy? Lacan's discourse theory suggests an answer based on an understanding of our human subjectivity, a subjectivity that implicitly seeks to overlook contradiction and ambiguity in our desire to fulfil human aspirations for a harmonious and secure world. This article will use Lacanian theory to examine the beliefs of the planning profession, how they are shaped and then implemented in our urban environments. In particular, Lacan's central theoretical premise of the Four Discourses will be explained and related to planning policy formulation. That is, how planners' acquire and internalise the discipline's diffuse sets of values, beliefs, knowledges and traditions, prior to then imposing them as urban policies on society.