This short paper will be presented at a panel on "Legal Positivism: For and Against?" at the annual meeting of the Association of American Law Schools in New Orleans, January 9, 2010. It attempts to identify the theoretical considerations that explain why legal positivism is the dominant view among legal philosophers. Three are identified: (1) positivism gives the best account of the ordinary understanding of law; (2) its account of law is the one deployed fruitfully in all empirical social science; and (3) it does not involve incredible or controversial metaphysical commitments. The paper concludes by noting that the competitors to legal positivism have narrowed considerably in recent years. American Legal Realism (as I have argued elsewhere) depends on a positivist theory of law, rather than being in competition with it. The most sophisticiated version of natural law theory, that of John Finnis, has conceded the main points in dispute to the legal positivists, and simply proposes changing the subject. And Dworkin's theory fails along the three dimensions of theoretical adequacy noted. 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, so do the positivist theories of Hart and Raz. Only atrocious public relations for legal positivism--aided and abetted by decades of misrepresentations by Dworkin – has led so many casual consumers of the jurisprudential literature to think otherwise. Thinking morality relevant to constitutional adjudication is no reason not to be a legal positivist.