به سادگی قاعده ی رفع تالی (اگر پی آنگاه کیو، کیو برقرار نیست، پس پی برقرار نیست): 

"Mackie ... chide Hare for overlooking the distinction between moral judgments and a metaethical account of the nature of moral judgments. Mackie allows that the difference would not matter to our everyday evaluations; but he thinks it does matter to philosophy. It matters so much, in fact, that in his opinion all our everyday value judgments are false, since all of them suppose, falsely, that there are values “in the world”. I am skeptical about the ethics–metaethics distinction, at least in this case. It seems to me that if it matters to the philosopher that all value judgments are false, it should matter to everyone else too. So, agreeing with Hare and Mackie that it doesn’t matter to everyone else, I conclude, with the satisfaction only an application of modus tollendo tollens can give, that it does not matter philosophically." 

Davidson, D. (1995) "The Objectivity of Value", In Problems of rationality