Derek Parfit -- a few comments
The fundamental problem Parfit is going to have is the idea that there is some "objective" content to facts that yield proper beliefs and, from that, actions. Facts, assuming they can be formulated in an objective way, which is not exactly a postmodern position, must then additionally yield objective implications. Even those who believe in objective facts may have problems with the notion that there are objective moral implications. Look, either there are or there aren't objective implications. If there are, then they are valid for all people, irrespective of a person's cultural background etc..., if there aren't, then the interpretations of facts are culturally relative. And this is assuming that the facts themselves have objective content. Of course, these days people these days say that facts are "value-laden" -- this is a way of describing the cultural relativity in the depiction of the "objective" world itself. The advantage of thi...