 is an immaterial body 
located at the surface (or at some surface) of a material object. Since the 
notion of a surface is essentially a topological one, and since the 
property of being immaterial is reflected in the morphological property of 
being fillable, the ontological basis is concerned first and foremost with 
the general dependence of a hole on its host.")"

This excerpt (and Achille and Roberto's book) seems to presuppose two basic 
(and distinct) ontological kinds; material and immaterial. Howe