In this book about metaphysics the author defends a realistic view of universals, characterizing the notion of universal by considering language and logic, the idea of possibility, hierarchies of universals, and causation. He argues that neither language nor logic is a reliable guide to the nature of reality and that basic universals are the fundamental type of universal and are central to causation. All assertions and predications about the natural world are ultimately founded on these basic universals. A distinction is drawn between unified particulars (which reveal natural principle of unity) and arbitrary particulars (which lack such a principle); unified particulars are the terms of causal relations and thus the real constituents of the world. The world is not made up of events but of unified particulars and basic universals.