Things are particulars and their qualities are universals, but do universals have an existence distinct from the particular things describable by those terms? And what must be their nature if they do? This book provides a careful and assured survey of the central issues of debate surrounding universals, in particular those issues that have been a crucial part of the emergence of contemporary analytic ontology. The book begins with a taxonomy of extreme nominalist, moderate nominalist, and realist positions on properties, and outlines the way each handles the phenomena of predication, resemblance, and abstract reference. The debate about properties and philosophical naturalism is also examined. Different forms of extreme nominalism, moderate nominalism, and minimalist realism are critiqued. Later chapters defend a traditional realist view of universals and examine the objections to realism from various infinite regresses, the difficulties in stating identity conditions for properties, and problems with realist accounts of knowledge of abstract objects. In addition, the debate between Platonists and Aristotelians is examined alongside a discussion of the relationship between properties and an adequate theory of existence. The book's final chapter explores the problem of individuating particulars. The book makes accessible a difficult topic without blunting the sophistication of argument required by a more advanced readership.