A careful reading of the evolution of the central dualism opposing public and private domains reveals the relatively silent presence of a third entity: the collective space. In comparison with the importance of a third way in economic and political fields, architecture seems to suffer from a significant gap. This transdisciplinary approach brings to light, in the architectural domain, the theoretical discontinuity that has long been given to intermediate space, between public space and private property. The architectural challenge around its own third way has long been reduced to the gradual register, without asserting itself as a status, necessary and complementary to the other two components of urbanity. As a very ancient urban element, and relatively recurrent in the formation of cities, collective space presents both all the transcendent abilities of reproduction, but also a precious flexibility mainly linked to its absence of theoretical formulation. Let’s give a new emancipated orientation to this underestimated component, overshadowed by a rooted binary reading of the city.