An exploration of the character and evolution of disgust and the role this emotion plays in our social and moral lives. People can be disgusted by the concrete and by the abstract -- by an object they find physically repellent or by an ideology or value system they find morally abhorrent. Different things will disgust different people, depending on individual sensibilities or cultural backgrounds. In Yuck!, Daniel Kelly investigates the character and evolution of disgust, with an emphasis on understanding the role this emotion has come to play in our social and moral lives. Disgust has recently been riding a swell of scholarly attention, especially from those in the cognitive sciences and those in the humanities in the midst of the "affective turn." Kelly proposes a cognitive model that can accommodate what we now know about disgust. He offers a new account of the evolution of disgust that builds on the model and argues that expressions of disgust are part of a sophisticated but largely automatic signaling system that humans use to transmit information about what to avoid in the local environment. He shows that many of the puzzling features of moral repugnance tinged with disgust are by-products of the imperfect fit between a cognitive system that evolved to protect against poisons and parasites and the social and moral issues on which it has been brought to bear. Kelly's account of this emotion provides a powerful argument against invoking disgust in the service of moral justification.