It is no easy task to define planning precisely, nor indeed to find a definitive term to describe it. As the eminent British planning scholar Peter Hall (1975) has noted: ‘Planning […] is an extremely ambiguous and difficult word to define. Planners of all kinds think that they know what it means’ (p. 3). This difficulty has a long history. For example, in 1951, Brown and Sherrard cautioned that there were dangers in attempting to ‘compress so comprehensive a subject into one short sentence’ (p. 3). Keeble in 1959 remarked that ‘town and country planning is not an easy subject to define’ (p. 9). Later, Campbell and Fainstein (1996) declared that planning is a ‘messy, contentious field’ without a single foundational paradigm. Today, the multitude of books, journal articles and websites that explain what planning ‘is’ and what planners ‘do’ attest to this ongoing problem.

Why is this the case? Is it because the theory and practice of planning emerge from several disciplinary areas and have evolved from different socio-political, economic and historical contexts? Is the problem related to the way planning is continually evolving as it responds to current situations, particularly environmental and social problems? Is it related to governments’ perceptions of planning and its functions? Is it because planners themselves cannot decide on the most important components of their practice? Or is it because communities demand different and often conflicting outcomes from their planners and planning processes?