Professor Eric Claeys is among the most thoughtful modern proponents of natural property rights. His new book, provided to conference participants in draft form, is typical of his rigorously analytical approach. It is an impressive articulation of a natural rights-based account of property. It significantly advances the debate over natural rights and should be taken seriously even by those who do not find it entirely convincing. There are real-world political stakes in abstract-seeming questions of property theory because natural rights are often deployed to limit government regulation of property. Natural rights contrast with positivist accounts that locate the content of property rights in the substance of positive law. Where property rig...