The literature on theoretical reason has been dominated by epistemological concerns, treatments of practical reason by ethical concerns. This book overcomes the limitations of dealing with each separately. It sets out a comprehensive theory of rationality applicable to both practical and theoretical reason. In both domains, Audi explains how experience grounds rationality, delineates the structure of central elements, and attacks the egocentric conception of rationality. He establishes the rationality of altruism and thereby supports major moral principles. The concluding part describes the pluralism and relativity his conception of rationality accommodates and, taking the unified account of theoretical and practical rationality in that light, constructs a theory of global rationality—the overall rationality of persons. Rich in narrative examples, intriguing analogies, and intuitively appealing arguments, this beautifully crafted book will spur advances in ethics and epistemology as well in philosophy of mind and action and the theory of rationality itself.