Moral Categories

The recent NYRB has an essay by Dworkin "What is a Good Life?", essentially promoting his new book on justice.  In the first section of the essay,"Morality and Happiness" Dworkin says that the content of moral principles "must be categorical."  It is, admittedly, a side remark; still, it is a commitment that should be rejected.  It is apparent that what is meant by the phrase is that the content of moral principles are categorical is something like what Kant advocated.  (If not, both the terminology and example chose by Dworkin are peculiar.)  To begin at the easy end of it, what example could be offered up as illustrating a moral principle whose content is categorical?  Surely, if that were so there would a few examples at hand.  There aren't.  No one has any remotely plausible samples to offer for consideration.  It is as though people put the entirety of history out of their heads when it comes to moral thinking, anthropology and biology disappear.  One thing to be said for Aristotle is his recognition that ethics is about the lives of living beings, little miserable material creatures.  That gets lost with the Kant.  Consider for a few minutes what sort of content could be categorical -- can you get to anything more meaningful than will the good or the like?  And that is just to say that there is no content.  It is not going to be a bar on lying or killing or holding other people as property.  It is not going to be treating people as means (how could there even be economic activity if that was the moral constraint?).