Scepticism about morality is as old as morality itself. Philosophers have attacked the `singular institution' of morality, but have these sceptics correctly identified their target? In this book a descriptive metaphysics of morals is presented, revealing how philosophical critics have consistently misidentified the institution of morality. Mark Platts' influential first book Ways of Meaning argued within the context of the philosophy of language that a `realist' account of moral thought was possible; Moral Realities defends the same possibility from the perspective of the philosophy of psychology. Platts engages the classical moral philosophies of Hume, Mandeville and Nietzsche, and tackles the powerful arguments of the contemporary moral relativists. His critique of the existing philosophical notions of desire and value enables him to clarify both what morality is and what it is not.