The first striking feature of Ethics is that the opening five chapters, which comprise part one, seek to establish the validity of natural law, an approach to moral inquiry based on the distinctive nature, faculties, and tendencies of the human being; this approach began with the ancient Greek philosophers and developed through the thought of Catholic and Protestant thinkers, such as St. Thomas Aquinas and Hugo Grotius. (For these religious philosophers, natural law was discoverable through reason, and was separable from theological questions.) One can judge Rothbard’s deep interest in this subject by his first four chapter titles: “Natural Law and Reason,” “Natural Law as ‘Science,'” “Natural Law versus Positive Law,” and “Natural Law and Natural Rights.”
Rothbard wanted us to read this material before moving on to such topics as property, enforceable rights, voluntary exchange, aggression, and self-defense. Why?
Because natural law gives meaning to and thus is indispensable to understanding those concepts. It provides the context. He approvingly quoted the natural-law philosopher John Wild: “The philosophy of natural law defends the rational dignity of the human individual.” He praised the English natural-law liberals (such as John Locke and the Levellers), “who transformed classical natural law into a theory grounded on methodological and hence political individualism.” And he identified the “great failing” of “classical” natural-law thinkers from Plato to Leo Strauss: they were “profoundly statist rather than individualist.”