INCLUSIVE v. EXCLUSIVE POSITIVISM
It is not easy to characterize natural-law theory in a way which captures what is more or less common to all theories going by that name. The same is true of positivism. Nevertheless, if pressed, one might reasonably identify natural-law theory as the view which affirms the proposition that there is a law, above ( Augustine and Aquinas) or implicit in ( Dworkin and Fuller) the explicit positive law in terms of which, necessarily, the existence and content of the latter can either be derived or challenged. It is no contingent accident that law and morality are connected: law just is a vehicle for the expression and enforcement of the moral law, or some particular element of it. Whether that element is to be identified with justice (as opposed to charity, benevolence, etc.) or with what Aquinas would have called 'exterior' as opposed to 'interior' movements,1 the point remains: it is in the very nature of law to express moral demands and affirm moral rights, whether these are rights of political morality, as in Dworkin, or rights affirmed in or derivable from God's Eternal law, as in Aquinas. A law could no more fail to express (perhaps inaccurately) a moral requirement than could the making of a promise.
In contrast with natural lawyers, defenders of legal positivism are thought to deny anything but contingent connections between law and morality. Law is capable of expressing and affirming moral demands and rights: but it is not in its nature necessarily to do so.____________________