cohen presents something like master argument for why there must be fact-independent principles;among which he place the fundamental principles of justice.Yet can any principles of conduct really be fact-independent? i do not think so,and the difference between my conception of political philosophy and the one have associated with Aristotle turns on which facts are to be attributed a grounding role. That would have been Aristotle's own opinion,if not Cohen's.However,I want to look closely at his master argument,even though it is rather abstract.Not only is its underlying mistake instructive.Cohen's view represent,as I have noted,the from this opposing conception must take if it is to deny that the tendency of reasonable people to disagree about moral matters has a bearing on the nature of justice and makes political philosophy a more autonomous discipline than simply applied moral philosophy.