Moral rationalism takes human reason and human rationality to be the key elements in an explanation of the nature of morality, moral judgment, and moral knowledge. This volume explores the resources of this rich philosophical tradition. It addresses questions such as whether and how moral knowledge could be a priori, whether and how rationalism can accommodate the growing empirical evidence of the role of emotion in moral cognition, and whether and how moral requirements can be grounded in practical rationality. Together the essays demonstrate that moral rationalism identifies not a single philosophical position but rather a family of philosophical positions, which resemble traditional rationalism, as exemplified by Kant, to varying degrees.