This book is a major contribution to the history of philosophy in the later medieval period (1250-1350). It focuses on cognitive theory, a subject of intense investigation during these years. In fact many of the issues that dominate philosophy of mind and epistemology today--intentionality, mental representation, skepticism, realism--were hotly debated in the later medieval period. The book offers a careful analysis of these debates, primarily through the work of Thomas Aquinas, Peter John Olivi, and William Ockham.