  A rather different argument appeals not so much to a metaphysical need for principles as to an epistemological need. If there is a distinction between right and wrong actions, how are we to detect it? There must be a detectable difference between the properties of the right ones and the properties of the wrong ones. Now if an action is wrong, it is wrong because of certain other features it has—the non-moral features that make it wrong. Those non-moral features will be detectable in the ordinary way, whatever that is. Good moral judges, having detected them, can somehow work out whether they make the action right or wrong. But if this ability is not a matter of magic, it must rest on an at least implicit knowledge of regularities connecting the non-moral features of actions and their moral properties. Moral principles specify such regularities. So if moral judgement is to be even possible, there must be a set of principles connecting moral properties to non-moral properties, contrary to what the particularist claims.