Four Kinds of Boundary : From an Ontological Point of View

Casati and Varzi have developed a theory of boundary based on extensional mereotopology and the distinction between fiat and bona fide boundaries. Firstly, I point out some problems in their theory that are related to the contact of bodies. Next, I propose a way of classification of boundaries into four kinds based on substance ontology and an alternative distinction between potential and actual boundaries. Finally, I will show that my way of classification makes it possible to solve the problems above.