Thus all these writers share in the project of constructing valid arguments which will move from premises concerning human nature as they understand it to be to conclusions about the authority of moral rules and precepts. I want to argue that any project of this form was bound to fail, because of an ineradicable discrepancy between their shared conception of moral rules and precepts on the one hand and what was shared—despite much larger divergences—in their conception of human nature on the other.
