There are a number of different kinds of natural law legal theories, differing from each other with respect to the role that morality plays in determining the authority of legal norms.The conceptual jurisprudence of John Austin provides a set of necessary and sufficient conditions for the existence of law that distinguishes law from non-law in every possible world.Lastly, Ronald Dworkin’s theory is a response and critique of legal positivism.
As John Austin describes the project, conceptual jurisprudence seeks "the essence or nature which is common to all laws that are properly so called" (Austin 1995, 11).
Accordingly, the task of conceptual jurisprudence is to provide a set of necessary and sufficient conditions for the existence of law that distinguishes law from non-law in every possible world.
On this peculiar view, the conceptual point of law would be to enforce those standards that are morally valid in virtue of cultural consensus.
For this reason, natural law theory of law is logically independent of natural law theory of morality.
But there is another kind of natural law theory having to do with the relationship of morality to law.
According to natural law theory of law, there is no clean division between the notion of law and the notion of morality. It refers to a type of moral theory, as well as to a type of legal theory, but the core claims of the two kinds of theory are logically independent.It does not refer to the laws of nature, the laws that science aims to describe.Classical natural law theory such as the theory of Thomas Aquinas focuses on the overlap between natural law moral and legal theories.Similarly, the neo-naturalism of John Finnis is a development of classical natural law theory. Fuller is a rejection of the conceptual naturalist idea that there are necessary moral constraints on the content of law.At the outset, it is important to distinguish two kinds of theory that go by the name of natural law.The first is a theory of morality that is roughly characterized by the following theses.One can deny natural law theory of law but hold a natural law theory of morality.John Austin, the most influential of the early legal positivists, for example, denied the Overlap Thesis but held something that resembles a natural law ethical theory.First, moral propositions have what is sometimes called objective standing in the sense that such propositions are the bearers of objective truth-value; that is, moral propositions can be objectively true or false.Though moral objectivism is sometimes equated with moral realism (see, e.g., Moore 1992, 190: "the truth of any moral proposition lies in its correspondence with a mind- and convention-independent moral reality"), the relationship between the two theories is controversial.