The central question in this book is why it seems reasonable for the words of our language to divide up the world in one way rather than another, or what the rational basis is for our language to contain certain kinds of general words rather than others. Terming this query the division problem, Dividing Reality aims to bring it into sharp focus, to distinguish it from various related problems, and to consider the best prospects for solving it. In exploring various possible responses to the division problem, Eli Hirsch examines a series of "division principles" which purport to express rational constraints on how our words ought to classify and individuate. The ensuing discussion deals with a wide range of metaphysical and epistemological topics, including projectibility and similarity, alternative analyses of natural properties and things, the inscrutability of reference, and the relevance of such pragmatic notions as salience and economy. The final chapters of the book develop what Hirsch contends is the most promising response to the division problem: a theory in which constraints on classification and individuation are seen to derive from the necessary structure of "fine-grained" propositions and the necessary dependence of some concepts on others. Formulating in clear terms a fundamental problem which has not been properly isolated or seriously addressed previously, this book is of key interest to metaphysicians, philosophers of language, and cognitive psychologists.