TPR, 80 (2) 2009 Luigi Mazza Centenary Paper Plan and constitution – Aristotle’s Hippodamus: towards an ‘ostensive’ definition of spatial planning Luigi Mazza is Professor of Planning in the Dipartimento di Architettura e Pianiicazione, Politecnico di Milano, via Bonardi 3, 20133 Milano, Italy; email: luigi.mazza@polimi.it This paper is part of ongoing research into the relationship between planning and citizenship. It focuses on two passages from Aristotle’s Politics. The first indicates that Hippodamus was a political philosopher and a planner and suggests that he cannot be considered the ‘inventor’ of the orthogonal grid, but rather may be regarded as the first to theorise about the division of population and land within the city and to establish the connection between plan and constitution, that is, between the plan and various forms of citizenship. In the second passage two models of spatial plan are set against each other as expressions of innovation and tradition and Aristotle discusses the difference between functional and aesthetic aims and prudence, i.e. technical rationality and political reason. On this basis the paper introduces the spatial inclusion/exclusion pairing as ‘a concept of planning’ and discusses some notes on rules, customs and tastes which may be helpful in designing a theory of a spatial plan. This paper, written by a planner, is particularly addressed to planners; since the author’s motives are not those of an antiquarian nor an amateur historian, to take an interest in Hippodamus twenty-ive centuries after his appearance on the stage of the Greek city may seem odd. The fact is that the subject of Hippodamus can be a starting point for an ‘ostensive’ deinition of spatial planning, in other words a deinition obtained by working back from historical examples of planning in order to address the general problem of whether a theoretical consideration of planning practices is possible. Hippodamus of Miletus is the irst town planner of whom a literary trace remains, even if indirect, and the irst town planner who reasoned about the space of the polis in the dual meaning of the Greek word: city-state and physical city. Hippodamus’ proposals are cited by Aristotle in two brief passages in his Politics, where Hippodamus is presented as a political philosopher and planner. Many writers on Hippodamus tend to overlook his twofold activity and to consider him only or above all as a planner, whereas the association of constitution and plan may be the key to the Aristotelian passage. In the following pages it will be argued that the interpretation of Aristotle’s text has been obstructed by the persistent idea among scholars that town planning is purely an instrument for spatial ordering and has no speciic links to politics. This idea is not untenable, but it does not help us to explore the essence of planning. Well before anyone else, when discussing Hippodamus Aristotle establishes an association