Just as the semantic teachings more or less related to logical positivism were at the heart of the S-naturalism of Scandinavian Realism, the new S-naturalism of writers such as David Brink, Michael Moore and Nicos Stavropoulos is engaged in the semantic revolution initiated by Hilary Putnam and Saul Kripke, known as the « new » or « causal » reference theory. These latter doctrines are – in any case – not museum pieces, so that derived jurisprudential theses are very lively objects of discussion. Stavropoulos explains the fundamental semantic ideas on which legal authors rely as follows: It is worth remembering that Hart himself constantly recommended trying to explain the law without presupposing controversial metaethical views. This recommendation may have been reasonable when Hart wrote, given the relatively undeveloped state of metaethics at the time and the narrow issues he addressed. In recent decades, however, debates in metaethics have become increasingly sophisticated, and there are now important viewpoints in jurisprudence that crucially depend on how these debates are resolved. The most important point of view for the purposes of the present case is in direct contradiction with Leiter`s naturalised presentation of the case-law. It is Dworkin`s view that all legal questions allow for only correct answers, determined by substantial moral insight. This view clearly presupposes that moral judgments allow even only correct answers, and therefore questions of metaethics cannot be fairly circumvented to judge this view. What should a naturalist say about this? The conventionality thesis emphasizes the conventional nature of the law and asserts that the social facts that lead to legal validity are decisive on the basis of a social convention. From this point of view, the criteria determining whether or not a particular rule is to be regarded as a rule of law are binding on the basis of an implied or express agreement between officials. For example, the Constitution of the United States is authoritative because of the conventional fact that it has been officially ratified by all fifty states. Second, Leiter enters into the more internal debates between inclusive and exclusive legal positivists over whether relevant tests of legality can include moral criteria. Leiter argues with some plausibility that proponents on both sides of this debate tended to rely on traditional forms of conceptual analysis and intuition pumping to support their respective views.

However, Leiter notes that these arguments did not resolve the issue of unsociability. Yet none of this should come as a surprise if, as the naturalist philosopher Leiter qua has argued, conceptual analysis alone is not sufficient to produce knowledge of what anything is, let alone the law. As mentioned above, Leiter suggested that, on the other hand, we can give a simple answer to this question if we instead ask ourselves what legal concept would make our best ongoing scientific research on law true and explanatory. The relevant empirical research programs are supposed to be those generated by legal realists, and these programs have produced the following claim: Although sources of law (as interpreted using the relevant canons of legal interpretation) sometimes determine the logically unambiguous outcomes of litigation, these sources can sometimes also leave legal issues undetermined. For this statement to be true and explanatory, we probably need to postulate a legal concept based entirely on the source; It is only in relation to such a concept that we can explain the particular category of judicial conduct at issue in this action as « determinative » and thus render the assertion true. Moreover, this notion is nothing other than the exclusive legal positivist conception of law, which does not allow the inclusion of moral criteria. When such considerations are valid, they lead to an important and distinctive set of considerations that favor exclusive legal positivism over its inclusive legal positivist and non-positivist rivals. Together, the essays in Part III can be read as a four-step argument that attempts to answer this question.

First, Leiter notes that some contemporary « naturalistic » moral realists sought to understand moral traits as a distinctive class of natural traits and articulated the criteria required to test the reality of these traits. (These criteria are a refined form of the metaphysical reality test mentioned at the beginning of this essay.) If such qualities existed, the objectivity of moral judgment could be justified in a purely naturalistic framework, but the existence of such qualities is partly an empirical question. Second, Leiter examines the predominant representations of such properties in the literature found in the work of Peter Railton and Nicholas Sturgeon, arguing that these relationships are empirically implausible. Third, Leiter discusses and criticizes several alternative, « unnatural » representations of moral objectivity that are primarily due to Dworkin and McDowell. Finally, Leiter concludes that objective legal judgment cannot depend on moral judgment and begins to develop a naturalistic representation of legal objectivity consistent with this limitation. Each of these varieties of naturalism has applications in the philosophy of law. In the philosophy of law, the substitutive forms of M-naturalism state: (1) the conceptual analysis of the concept of law should be replaced by the recourse to the best social science explanations of legal phenomena, and (2) the normative theories of jurisprudence should be replaced by empirical theories. These views are related to American legal realism and Brian Leiter`s reinterpretation of realism.

Normative M-naturalists, on the other hand, inspired and directed by Alvin Goldman, seek empirical results on philosophical and fundamental questions of jurisprudence, legal rules of evidence and discovery, adversarial processes, etc. Finally, s-naturalism has played a prominent role in the writings of Scandinavian legal realists (long before the resurgence of naturalism in English-speaking jurisprudence), whose ontological s-naturalism has led them to employ a familiar palette of naturalism-motivated explanatory strategies, including the naturalistic reduction of legal concepts and non-cognitivist representations of important aspects of legal discourse. S-naturalism can also serve as a motivation for legal positivism in the Anglo-American jurisprudential tradition and has sometimes served. New forms of S-naturalism, coupled with a revival of a kind of theory of natural law championed by David Brink and Michael Moore, among others, apply the « new » or « causal » reference theory to questions of legal interpretation, including the interpretation of moral concepts as they appear in legal rules.