The Ontology of Haecceities

This book deals with the Problem of Distinction, i.e. what explains the distinction of two substances, especially when they are qualitatively indiscernible? It argues that the best solution to this problem is an ontology of haecceities, properties like "being identical with X" which is unique for X and responsible for its individuation. After a detailed examination of various metaphysical positions including the bundle theory and the bare particularism, the author develops a novel ontology of haecceities. A Haecceity Mereology with three rules is proposed. According to this ontology, the reality is constituted by two fundamental kinds of properties, universals and haecceities. An individual substance is a special mereological sum of a haecceity and its correspondent universals.