This experimental series of sessions brings together DUSP faculty and others to debate key issues in applied planning theory, while providing a parallel opportunity for incoming doctoral students to consider a range of ideas and perspectives that cover many aspects of planning and development. Sessions focus on questions of livability, territoriality, governance, and reflective practice. These four overarching ideas form the framework used in the required text, Planning Ideas That Matter, edited by Bishwapriya Sanyal, Lawrence J. Vale, and Christina D. Rosan (MIT Press, 2012). The intent of the debates is to identify some of the “planning ideas that matter” while opening up the question of just what a “planning idea” might actually entail. The debates and associated seminar cannot be either a full “history of planning theory” or, for that matter, a “theory of planning history,” but instead can provide windows into thinking about what such frameworks ought to include. We want to encourage participants to identify the “planning ideas” that matter most to them. The course is co-caught by Prof. Larry Vale and Prof. Jinhua Zhao