Rational Sentimentalism develops a novel theory of the sentimental values. These values, which include the funny, the disgusting, and the shameful, are profoundly important because they set standards for emotional responses that are part of our shared human nature. Yet moral philosophers have neglected them relative to their prominent role in human mental life. The theory is sentimentalist because it holds that these values are emotion-dependent-contrary to some prominent accounts of the funny and the disgusting. Its rational aspect arises from its insistence that the shameful (for example) is not whatever elicits shame but what makes shame fitting. Shameful traits provide reasons to be ashamed that do not depend on whether one is disposed to be ashamed of them. Furthermore, these reasons to be ashamed transmit to reasons to act as shame dictates: to conceal. Sentimentalism requires a compatible theory of emotion and emotional fittingness. This book explicates a motivational theory of emotion that explains the peculiarities of emotional motivation as other theories cannot. It argues that a class of emotions are psychological kinds with a similar goal across cultures despite differences in their elicitors. It then develops an account of fittingness that helps to differentiate reasons of fit, which bear on the sentimental values, from other considerations for or against having an emotion.Significant and controversial conclusions emerge from this theory of rational sentimentalism. Sentimental values conflict with one another, and with morality, but nevertheless provide practical reasons that apply to humans-if not to all rational agents.