 The argument just sketched would locate the moral error in a mistake we make about the kind of creatures we are. The more widely discussed arguments, however, locate the moral error in a mistake we make about the kind of world we inhabit. John Mackie (who coined the term “error theory” in 1977) argues that when we participate in moral discourse we commit ourselves to the existence of objective values and objective prescriptions, but there are no such things. Essentially, Mackie argues that the moral realist is correct about morality conceptually speaking—we are moral realists—but the moral realist is incorrect about how the world actually is. Moral facts place demands upon us, but (Mackie asks) how could such demands exist objectively? This would seem to require rules of conduct somehow written into the fabric of the universe, and nothing in our understanding of the objective naturalistic world (Mackie goes on) suggests that anything of the kind exists. Mackie famously calls such properties “queer” (in what seems now an increasingly anachronistic use of the term).