As anybody who has an interest in metaphysics will know, a book on
metaphysics can cover any number of topics, from free will and determinism
to causality, arguments for the existence of God, the problem of
evil, why there is something rather than nothing, personal identity, the
nature of space and time, propositions, and possible worlds and possibilia,
to name just a few. While it is perfectly legitimate to include any,
or all, of these topics in a book on metaphysics, I have come to think
that many of them presuppose an understanding of basic topics and
issues in ontology, the study of what sorts or kinds of things there are
in the world. For example, discussions of causality presume an understanding
of what sorts of things are involved in causal relations, whether
these be events, states, or facts, and also of what sorts of things causal
laws relate (whether they relate properties, conceived of as universals, or
classes of tropes, for example). The topics in ontology, to my mind, raise
some of the most fundamental and interesting questions in metaphysics
and, more generally, in philosophy.
Not surprisingly, then, this book is a study in ontology. In it I offer
a systematic way of thinking through a central question of metaphysics
– what are the most fundamental kinds of things that exist? I begin
with a thorough and accessible discussion of the nature and aims
of metaphysics and of the tools that can be used to engage in
metaphysical thinking about different ontological categories. I then
employ these tools in order to explore diverse views about various categories
of things, such as material substances, persons, and events, as
well as universals, examining the realist/nominalist debate. The book
both surveys existing accounts of the natures of these kinds of things
and argues for substantial original positions of its own. The arguments
support a systematically anti-reductionist view of the basic ontological
categories.