Outline moral realism and explain how Mackie’s argument from queerness opposes this view.

Moral realism is a metaethical view composed of a semantic and a metaphysical claim. The semantic claim, cognitivism about moral discourse, holds that moral judgements are robustly truth-apt. The metaphysical claim, realism about morality, holds that at least some moral judgements are true, and that they are true in virtue of some mind-independent moral facts. Moral realist theories can be usefully divided into two categories: moral naturalism (which holds moral facts to be amongst the natural facts) and moral non-naturalism (which holds moral facts to be amongst the non-natural facts). Mackie’s ‘Argument from Queerness’ (AQ) is designed to refute non-naturalist moral realism (NNMR) – espoused for example by Plato and G.E. Moore – and, as such, my answer will explain the operation of AQ solely in relation to this form of realism. To start with, Mackie’s AQ does not target moral cognitivism. Indeed, Mackie holds that speakers’ moral claims – such as “Murder is wrong” – aim at truth. Crucially, however, he also holds that all such moral claims are false; moral discourse, Mackie claims, is massively in error. As an abductive or probabilistic argument against NNMR, Mackie’s AQ aims to demonstrate that moral claims (when understood as attempts to describe a non-natural and mind-independent moral reality) are deeply improbable, even if not impossible. The AQ defends this improbability with two distinct arguments, metaphysical and epistemological. With his metaphysical argument, Mackie suggests that mind-independent moral properties, were they to exist, would have to be intrinsically motivating or “objectively prescriptive”. That is, merely knowing that murder has the properties of wrongness should be sufficient to motivate one to refrain from murdering, without any further psychological or social factors coming into play. But such a property of inbuilt “to-be-pursuedness”, as Mackie calls it, is not found anywhere else in our naturalistic worldview. Therefore, Mackie argues, the existence of mind-independent moral properties is highly improbable. With his epistemological argument, Mackie suggests that if NNMR is correct, then objectively prescriptive moral properties should be in some way apprehensible by human subjects, for it is such apprehension that leads subjects to make moral claims. But if humans were able to apprehend such properties, Mackie argues, then they would have to do so by employing a faculty utterly different to those we use to detect everyday properties, like smell, appearance, or logical truth. We cannot reach moral conclusions using perception, for non-natural properties, being non-physical, cannot be directly perceived. Nor can we use deduction, for properties we deduce (like logical truth) are not motivating in the way moral properties are supposed to be. Therefore, Mackie concludes, it is highly improbable that the properties that subjects refer to with moral statements really exist.