ABSTRACT
In this chapter, we raise the philosophical question of the ontology of planets. This seems necessary if we are to theorize about the premises, challenges and promises of space exploration. We map the philosophical terrain for our understanding of the ontology of planets as a core concept for the space age, by reflecting on the ontology of planet Earth. We first distinguish between Earth and World and argue that the ontology of Earth provides access to the ontology of planets. Subsequently, we develop three principles that constitute the ontology of planet Earth and can inform a more general ontology of planets: 1) the conativity of the materiality of planets establishes the identity of those material entities that constitute planets; 2) the non-identity or pre-individual generative capacity of the materiality of planets constitutes the identity of material entities and always res-cends actual and possible material entities as differentiations from this undifferentiated materiality of planets; 3) the responsiveness of material entities to other material entities builds the eco-system or World in which we live and act. In this context, we consider the materiality of planets as possible grounds of heterogenous Worlds on other planets.
