This chapter is an attempt to use the concept of the ‘trading zone’, as elaborated by Peter Galison (1999) in the field of the history of science, to indicate new opportunities for fostering innovation in planning, beyond the illusion of conquering a general consensus about values and objectives among the different actors involved in strategic planning. To do this, I will first illustrate how, in the field of planning, there has been for a long period a kind of mirroring between the debate about rationality, rooted in political science, and the development of the theory of planning (Webber, 1969; Faludi, 1973), a process of mirroring that was somehow suspended when the most complex decision-making model was proposed by Cohen, March and Olsen in 1972, the so-called ‘garbage can model’: a provocative theory that emphasized the extreme complexity of collective decision-making processes. My point is that we have to re-start today from that kind of complexity to elaborate a vision of strategic planning which is adequate to the emerging problems of the contemporary city. The ‘trading zone’ concept is a promising tool to move us in that direction.