The conundrum between what is just and what is unjust in space is further complicate by the “tragedy of the commons” as explained by Hardin in his now classic article of 1968 (Hardin, 1968). According to Hardin, the use of common resources (such as space) is regulated by self-interest. As men draw from common resources, they try to maximize their individual gains, all the while producing negative and positive externalities that are shared by all. Hardin was able to demonstrate that the ‘invisible hand’ of Adam Smith is seldom able to generate the necessary societal benefits assigned to the continuous pursuit of self-interested gains by rational agents. As men draw from a common pool of resources, they pursue self-interested individual gain, and produce positive externalities that benefit all. But the negative externalities produced are shared by all as well, so the incentives to draw from the resources are very high, while the incentives to self-restraint to preserve the resource or to limit negative externalities are low.

We posit that Spatial Planning is, or could potentially be, an instrument of spatial justice, in the sense that it is one of the formal institutions societies have drawn to regulate the distribution of spatial benefits and burdens.  We know that in reality Spatial Planning is often used to advance private interests and to increase returns for those who already benefit from an unjust distribution of spatial resources. But this does not diminish the potential of the institution to promote justice. Following this logic, spatial justice has another dimension, beyond the just distribution of spatial benefits and burdens: the procedures through which decisions are taken to allocate burdens and benefits of development must also be just. Fair, inclusive and accountable procedures are likely to deliver just outcomes. This is what we call Procedural Spatial Justice.

In summary, spatial justice has two main dimensions: distributive and procedural. On one hand, the burdens and benefits of social cooperation must be fairly spatially distributed and made accessible (distributive spatial justice) and on the other hand, the procedures through which decisions are taken must also be just (procedural spatial justice). The assumption is that if the procedures are just and inclusive, the outcome (the distribution of burdens and benefits) will also be just.