Marc A. Hight has given us a well-researched, well-written, analytically rigorous and thoughtprovoking book about the development of idea ontology in the seventeenth and early eighteenth centuries. The book covers a great deal of material, some in significant depth, some not. The figures discussed include Descartes, Malebranche, Arnauld, Locke, Leibniz, Berkeley, and Hume. Some might think it a tall order for anyone to grapple with the central works of these figures on a subject as fundamental as the nature of ideas. And while reading the book, I must admit to having had this thought a few times. Seventeen pages on Descartes’ theory of ideas, covering the development of his ontology of ideas, the distinction between formal reality and objective reality, the nature of mental representation, the contagion theory of causation, the doctrine of innate ideas as ungrounded dispositions, and the interactionism/occasionalism controversy? Wow. And yet Hight has done his homework. He knows the figures and the relevant interpretive controversies well, he focuses on many of the passages that are relevant to the book’s central thesis, and in the end offers us a compelling narrative as an alternative to what he identifies as