This work is ”a systematic ontology.” Ontology is the study of *being* as such, and a systematic ontology is an account of the most fundamental ways of *being* something or other – of what they are and of how they are related to each other. The questions it pursues are not primarily about what *causes* things, but about what things *are* or consist in – though causal questions cannot be totally avoided. The title of the work, *What Is, and What Is in Itself* , marks the most important distinction in ways of being. What *is* includes everything there is, but not everything there is included in what *is in itself*. The first five chapters of the book define and examine the ways of being: in chapters 1 and 2, being actual or existing, or even just being something without existing or being actual; in chapter 3, being an intentional object, and perhaps a *merely* intentional object; in chapter 4, relations between things and their properties; and in chapter 5, being a thing in itself. Chapter 6 discusses whether only conscious beings are things in themselves, and suggests an affirmative answer. Chapter 7 discusses the epistemology of ontology. Chapters 8 and 9 discuss issues about thisness and identity. And chapters 10 and 11 discuss mainly occasionalist and panentheist answers to questions about the causal unity of the universe.