Economics can help supply much of the data for a libertarian position, but it cannot establish that political philosophy itself. Political judgments are necessarily value judgments, political philosophy is therefore necessarily ethical, and hence a positive ethical system must be set forth to establish the case for individual liberty.
The present work attempts to fill this gap, to set forth a systematic ethical theory of liberty. It is not, however, a work in ethics per se, but only in that subset of ethics devoted to political philosophy. Hence, it does not try to prove or establish the ethics or ontology of natural law, which provide the groundwork for the political theory set forth in this book. Natural law has been ably expounded and defended elsewhere by ethical philosophers.
The key to the theory of liberty is the establishment of the rights of private property for each individual's justified sphere of free action can only be set forth if his rights of property are analyzed and established. "Crime" can then be defined and properly analyzed as a violent invasion or aggression against the just property of another individual (including his property in his own person). The positive theory of liberty then becomes an analysis of what can be considered property rights, and therefore what can be considered crimes. Various difficult but vitally important problems can then be dissected, including the rights of children, the proper theory of contracts as transfers of property titles, the thorny questions of enforcement and punishment, and many others. Since questions of property and crime are essentially legal questions, our theory of liberty necessarily sets forth an ethical theory of what law concretely should be. In short, as a natural-law theory should properly do, it sets forth a normative theory of law—in our case, a theory of "libertarian law."
.. it is not the business of law—properly the rules and instrumentalities by which person and property are violently defended—to make people moral by use of legal violence.