John Rawls: Everyday morality isn’t simple to explain

A useful comparison here is with the problem of describing the sense of grammaticalness that we have for the sentences of our native language.  In this case the aim is to characterize the ability to recognize well-formed sentences by formulating clearly expressed principles which make the same discriminations as the native speaker.  This undertaking is known to require theoretical constructions that far outrun the ad hoc precepts of our explicit grammatical knowledge.  A similar situation presumably holds in moral theory.  There is no reason to assume that our sense of justice can be adequately characterized by familiar common sense precepts, or derived from the more obvious learning principles.  A correct account of moral capacities will certainly involve principles and theoretical constructions which go much beyond the norms and standards cited in everyday life; it may eventually require fairly sophisticated mathematics as well.

from A Theory of Justice by John Rawls (revised edition), pp 41-42.

I like this comparison, although I think familiar common-sense precepts are more useful for moral theory than the ad-hoc precepts of our explicit grammatical knowledge are for syntactic theory.  Telling people not to split infinitives or end sentences with a preposition does nothing to explain why  “the go store I need” is a sentence of English you’ll never hear from a native speaker.  Telling people to do to others what they want done to them will go some distance to explain why we judge physical assault as immoral in most cases.  Of course that’s just some raw material for a theory.  There’s lots and lots of work to be done after that.