This book presents an ethical theory that uniquely integrates naturalistic and rationalistic elements. Robert Audi develops his theory in four areas: moral epistemology, the metaphysics of ethics, moral psychology, and the foundations of ethics. Comprising both new and published work, the book sets forth a moderate intuitionism, clarifies the relation between reason and motivation, constructs a theory of intrinsic value and its place in moral obligation, and presents a sophisticated account of moral justification. The concluding chapter articulates a new normative framework built from both Kantian and intuitionist elements. Connecting ethics in novel ways to both the theory of value and the philosophy of action, the essays explore topics such as ethical intuition, reason and judgement, and virtue. Audi also considers major views in the history of ethics, including those of Aristotle, Hume, Kant, Mill, Moore, and W. D. Ross, and engages contemporary work on autonomy, responsibility, objectivity, reasons, and other issues. Clear and conceptually rich, this book makes vital reading for students and scholars of ethics.