This was a keynote address at the annual meeting of the Australasian Society of Legal Philosophy at the University of Sydney in 2013. (It is a much expanded version of some brief remarks presented in 2010.)
Why is legal positivism the dominant view among legal philosophers? The address begins with a somewhat lengthy methodological preamble, offering reasons to resist the extravagant metaphysical inflation of the purported theoretical virtues of positivism in some recent jurisprudential writing by Dickson and Shapiro, among others. Artifacts do not have essential attributes, not even functional ones. (Leslie Green's partial resistance to my metaphysical deflation in his recent "The Morality in Law" is shown to depend on some confusions about the status of the claim that law is an artifact.) I then suggest that legal positivism has three theoretical virtues counting in its favor. First, if we take seriously the benchmark for theoretical adequacy that Hart gave for his theory--namely, that it capture what the ordinary educated person familiar with a modern municipal legal system understands by the concept of law--that positivism does the best job of accounting for this ordinary understanding. (Particular attention is drawn to Raz's original arguments for legal positivism of this form, as opposed to his perhaps better-known, if more controversial, argument from the nature of authority.) Second, the positivist account of law is the one deployed fruitfully in all the empirical social sciences. Third, the positivist theory does not involve incredible or controversial metaphysical assumptions. The last two theoretical considerations are acknowledged to presuppose naturalism, but I suggest that doing so is unavoidable.
Are there any competitors to the positivist theory so understood? The most sophisticiated version of natural law theory, that of John Finnis, has conceded the main points in dispute to the legal positivists, and fails to articulate a successful argument against descriptive jurisprudence. A plausible theoretical reconstruction of the jurisprudence of American Legal Realism shows it to presuppose the positivist view. Scandinavian Legal Realism is shown to reject Hart's benchmark of theoretical adequacy (the first point, above), and so to be undertaking a wholly different project, one in no competition with Hart's. Dworkin's theory, by contrast, fails along the the three dimensions of theoretical adequacy along which legal positivism succeeds.
The paper concludes that the appeal of Dworkin's theory to constitutional lawyers in the Anglophone world and elsewhere is due entirely to the (correct) perception that his theory makes moral considerations relevant to the resolution of momentous constitutional questions; unfortunately, nothing in the positivist theories of Hart and Raz denies the relevance of moral considerations to such questions. I end with some sociological reflections on jurisprudence that may partly explain the continued resistance to legal positivism, contrasting my own sociological speculations with Dworkin's final and embarrassing ad hominem arguments against legal positivism.