  Moral nihilism here is not about what is semantically or metaphysically possible. It is just a substantive, negative, existential claim that there does not exist anything that is morally wrong. It is, however, usually supplemented with an explanation of why people hold moral beliefs that are false (just as the story of Descartes’s deceiving demon is supposed to explain why our perceptual beliefs are false). This thesis of moral nihilism has been supported by various reasons, including the pervasiveness of moral disagreement and our supposed ability (with the help of sociobiology and other sciences) to explain moral beliefs without reference to moral facts. Since people do take moral nihilism seriously and even argue for it (Mackie 1977, Joyce 2001), moral nihilism cannot be dismissed as readily as Descartes’s deceiving demon.