Error Theory: Mackie's Argument from Queerness

John Leslie Mackie's Ethics: Inventing Right and Wrong (1977) advances one of the most radical positions available in metaethics: moral error theory. Mackie agrees with moral realists on a crucial semantic point — ordinary moral discourse is cognitivist, meaning that moral statements purport to state facts and are genuinely truth-apt — but he denies that any of them are ever true, because the objective moral facts and properties that such statements purport to describe simply do not exist. Error theory is therefore a global skepticism about first-order moral claims combined with a robust semantic realism about moral language: when someone asserts "cruelty is wrong," the theory holds that the sentence is meaningful, and asserts something, but that the assertion is false.