WikimediaWikimediaIn 1982 Murray Rothbard published his magnum opus in political philosophy, The Ethics of Liberty. It is a tour de force, a remarkable presentation of the moral case for political freedom. What a complement to Man, Economy, and State and Power and Market, Rothbard’s towering contributions to our understanding of free markets!

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."

Rothbard’s conviction that individual rights are derived from something more fundamental can be seen in this statement: "The myriad of post-Locke and post-Leveller natural-rights theorists made clear their view that these rights stem from the nature of man and of the world around him."

For Rothbard, individual rights boil down to the right to be free from aggression. (Thus complete freedom in society is possible and realistic.) This is what he wished to derive from the natural law. The principle is not self-evident (though it surely has intuitive appeal). It is no free-floating iceberg. Rather, it follows from earlier findings that reason discloses about human nature ("the primordial natural fact[s] of freedom" and self-ownership), human action, the nature of the world around us, and the conditions under which we may flourish. The book does not discuss the nature of aggression until the third chapter of part two:  "A Theory of Liberty" (chapter 8 in the book).

Readers who are eager to get on to Rothbard’s discussion of the Nonaggression Principle—which I think is better expressed as the Nonaggression Obligation—may be tempted to skip part one. To them I have three words of sage advice: Don’t do it! You will deny yourself the full benefit of this marvelous book. Read and enjoy the discussion of natural law.

For Rothbard, natural law concerns the discovery of objective values and objective ethics. He writes:

In the Thomistic tradition, natural law is ethical as well as physical law; and the instrument by which man apprehends such law is his reason — not faith, or intuition, or grace, revelation, or anything else. In the contemporary atmosphere of sharp dichotomy between natural law and reason — and especially amid the irrationalist sentiments of “conservative” thought — this cannot be underscored too often.

With obvious approval he quoted William J. Kenealy, a Jesuit priest, who wrote:

This philosophy maintains that there is in fact an objective moral order within the range of human intelligence, to which human societies are bound in conscience to conform and upon which the peace and happiness of personal, national and international life depend. [Emphasis added.]

Rothbard then asked a question posed by another natural-law philosopher, John Wild: "Why are such principles felt to be binding on me?" And he supplied Wild’s answer:

The factual needs which underlie the whole procedure are common to man. The values founded on them are universal. Hence, if I made no mistake in my tendential analysis of human nature, and if I understand myself, I must exemplify the tendency and must feel it subjectively as an imperative urge to action.

Or, Rothbard adds, as 19th-century American Unitarian minister William Ellery Channing put it, "All men have the same rational nature and the same power of conscience, and all are equally made for indefinite improvement of these divine faculties and for the happiness to be found in their virtuous use."

Much modern philosophy dismisses natural law as old-fashioned and unscientific, but Rothbard endorsed Étienne Gilson’s observation, "The natural law always buries its undertakers."

Now here is a puzzle. On the one hand, Rothbard emphasized that natural-law philosophy seeks to identify that which is objectively good for all human beings. He writes:

Aquinas, then, realized that men always act purposively, but also went beyond this to argue that ends can also be apprehended by reason as either objectively good or bad for man. Moral conduct is therefore conduct in accord with right reason.


If, then, the natural law is discovered by reason from [quoting Edwin W. Patterson] "the basic inclinations of human nature … absolute, immutable, and of universal validity for all times and places," it follows that the natural law provides an objective set of ethical norms by which to gauge human actions at any time or place.

And, finally, "The natural law, then, elucidates what is best for man—what ends man should pursue that are most harmonious with, and best tend to fulfill, his nature."

But on the other hand, Rothbard was an economist in the Austrian tradition, which holds that value is subjective. Can this paradox be resolved?

Rather easily, it turns out. Rothbard wrote:

The natural law, then, elucidates what is best for man—what ends man should pursue that are most harmonious with, and best tend to fulfill, his nature. In a significant sense, then, natural law provides man with a "science of happiness," with the paths which will lead to his real happiness. In contrast, praxeology or economics, as well as the utilitarian philosophy with which this science has been closely allied, treat "happiness" in the purely formal sense as the fulfillment of those ends which people happen—for whatever reason—to place high on their scales of value. Satisfaction of those ends yields to man his "utility" or "satisfaction" or "happiness." Value in the sense of valuation or utility is purely subjective, and decided by each individual. This procedure is perfectly proper for the formal science of praxeology, or economic theory, but not necessarily elsewhere. For in natural-law ethics, ends are demonstrated to be good or bad for man in varying degrees; value here is objective—determined by the natural law of man’s being, and here "happiness" for man is considered in the commonsensical, contextual sense.

Many of these quotations indicate that Rothbard believed that under natural law, binding moral constraints can be rationally identified. Respect for other people and their just possession is one such binding constraint; it does not require explicit or implicit consent. I wish he had developed this point further because it seems crucial to the libertarian case. Why do we owe other people nonaggression? What is the nature of that obligation? (I discuss this question in "What Social Animals Owe to Each Other.")

Instead, Rothbard, in part two, seemed to shift ground and offer other reasons for respecting people’s rights. He wrote that any proposed political ethic that permits some to rule others fails the test of universalizability; an objective moral code must be applicable to everyone. (This sounds like one of Kant’s formulations of the categorical imperative.) He also wrote that living parasitically off of other people conflicts with the exploiter’s own self-interest because it reduces the volume of goods produced while violating his nature:

Coercive exploitation or parasitism injure the processes of production for everyone in the society. Any way that it may be considered, parasitic predation and robbery violate not only the nature of the victim whose self and product are violated, but also the nature of the aggressor himself, who abandons the natural way of production—of using his mind to transform nature and exchange with other producers—for the way of parasitic expropriation of the work and product of others. In the deepest sense, the aggressor injures himself as well as his unfortunate victim.

True enough, but why ought one, first, act only in accord with a universal ethic and, second, not exploit others if one were to calculate that in a great society the reduction in the volume of goods would be only marginal? Why exactly is an exploiter harmed because he loots rather than produces? Or, what exactly is the price to be paid for not living in harmony with one’s nature as a human being?

In fairness to Rothbard, he did not set out to formulate a complete ethical philosophy, just the subset of ethics dealing with aggression. He likely believed that a complete ethics had already been formulated by others. (He cited several Aristotelian and Thomist thinkers and was influenced by the Aristotelian novelist-philosopher Ayn Rand, although he did not cite her.) So why reinvent the wheel?

My questions aside, The Ethics of Liberty is a great book that deserves the attention of anyone interested in the good society and human flourishing.

This article originally appeared at the Future of Freedom Foundation.