way divide ontologies notion ontological hierarchy hierarchical ontologies assert entities exist fundamental level entities depend flat ontologies hand deny privileged status entities jonathan schaffer provides overview positions distinguishing ''flat'' ontologies non hierarchical ' 'sorted'' ontologies polycategorical non hierarchical ''ordered'' ontologies polycategorical hierarchical ref name schaffer ref ''flat'' ontologies interested difference existence non existence ''flat'' flat ontology represented simple set containing entities
Humanities Philosophy Metaphysics Ontology