On Metaphysics was first published in 1989. On Metaphysics brings together eighteen essays by a self-described analytic philosopher who is concerned with redirecting the linguistic emphasis in contemporary philosophy toward the traditional questions of metaphysics. The essays explore the most fundamental categories of reality: substance and attribute; parts and wholes; human freedom and the self; coming into being and passing away; and the nature of objective reference. Chisholm combines an “internal” approach to theory of knowledge with an “intentional” approach to metaphysics. The book thus presupposes that the self is better known to the self that is any other individual thing, and that our knowledge of ourselves provides us with the key to understanding the problems of ontology. Chisholm has made both minor and major revisions in many of the essays since their initial publication. “The Categories,” written expressly for this book, represents a summation of the ontology set forth in On Metaphysics.