The Ethics of Liberty is a 1982 book by American philosopher and economist Murray N. Rothbard, in which the author expounds a libertarian political position. Hans-Hermann Hoppe's Introduction to the 1998 edition of the book claims that it "explains the integration of economics and ethics via the joint concept of property; and based on the concept of property, and in conjunction with a few general empirical (biological and physical) observations or assumptions, Rothbard deduces the corpus of libertarian law, from the law of appropriation to that of contracts and punishment." Rothbard's argument is based on a form of natural law ethics, and makes a case for anarcho-capitalism. Summary The Ethics of Liberty is divided into five parts, although a previous edition lacked the fifth. Part I is an introduction, which explains the outlines of natural law theory in general and defends it briefly against some objections. Part II is the substance of the work itself, setting forth Rothbard's ethics regarding the use of force. Part III applies his ethical theories to the State, which he viewed as "the inherent enemy of liberty and, indeed, of genuine law". Part IV offers brief reviews of alternative political theories developed by Mises, Hayek, Berlin, and Nozick. Part V attempts to set forth a theory of strategy of how to move from the present system to a libertarian anarcho-capitalist society. Part I: Introduction: Natural Law Chapter 1, "Natural Law and Reason", defends natural law theory in general. Many modern political philosophers, according to Rothbard, reject the idea of natural law, dismissing it as a theological concept. Against them, Rothbard argues that natural law can be rationally established, without the need for theology. The Thomist tradition, for example, asserts the independence of philosophy from theology and the ability of man's reason to understand the laws of the natural order. Rothbard claims that this position is not anti-religious, as it leaves open the question of whether or not God has created that order or given man the ability to reason. He concludes by referencing Hugo Grotius and his successors, who elaborated an independent body of natural laws in order to construct a system of laws that would carry conviction in an age when theological controversy was losing its power. Chapter 2, "Natural Law as 'Science'", argues that the concept of natural law is not mystical, but a scientific observation of entities and their behavior. If things