Why Legal Positivism (Again)?

I gave a very short talk on this topic a few years ago, but this new draft paper is a much expanded and more systematic discussion, given as a keynote address in August for the annual meeting of the Australasian Society of Legal Philosophy in Sydney.  I hope it will interest some readers, and I would especially encourage those outside general jurisprudence but with some interest in the philosophy of law to take a look, since I hope it clears up some common confusions about positivism and about Dworkin's theory of law.