Although there is a huge literature on Nietzsche's philosophy, this is the first study in English that focuses on his ontology. Before proceeding to that ontology, Addis argues that, contrary to many commentators, Nietzsche defends both the possibility and the desirability of objectivity in the search for knowledge, including knowledge of the basic features of reality, that is, of ontology. In separate chapters, Addis then sets out, analyzes, and evaluates the five essential components of Nietzsche's ontology: constant change, substances and things, minds, causation, and will to power. In each case, Addis contributes an original understanding of the feature under discussion, with more detail than exists in other treatments, and defended with quotes from relevant texts of Nietzsche.