[Editor's Note: Year by year, "natural law theory" has been gaining acceptance as the ontology of choice--or the last gasp--of not only social religio-conservatism but of classical philosophy as well. Time for a reprise of our 2009 Natural Law Theory post.
Who better to explain it than Murray Rothbard [1926-1995]? An interesting fellow---an atheist, a libertarian...and a Thomist, meaning Thomas Aquinas' "Scholastic" system of looking at things.
There's a common perception today that "reason" was somehow discovered in the West with the Enlightenment. But reason had a seat at the table long before David Hume and the skeptics, and although the Founders didn't quote Aquinas (1225-1274 CE) because he was associated with Roman Catholicism (boo, hiss), his influence carried through 500 years through the "Schoolmen" to the Protestants Hugo Grotius and Richard Hooker, then through Locke, and then to the Founding generation.]
From Rothbard's The Ethics of Liberty (read the whole thing!):
AMONG INTELLECTUALS WHO CONSIDER themselves "scientific," the phrase "the nature of man” apt to have the effect of a red flag on a bull. "Man has no nature!" is the modern rallying cry; and typical of the sentiment of political philosophers today was the assertion of a distinguished political theorist some years ago before a meeting of the American Political Science Association that "man's nature" is a purely theological concept that must be dismissed from any scientific discussion.
In the controversy over man's nature, and over the broader and more controversial concept of "natural law," both sides have repeatedly proclaimed that natural law and theology are inextricably intertwined. As a result, many champions of natural law, in scientific or philosophic circles, have gravely weakened their case by implying that rational, philosophical methods alone cannot establish such law: that theological faith is necessary to maintain the concept. On the other hand, the opponents of natural law have gleefully agreed; since faith in the supernatural is deemed necessary to belief in natural law, the latter concept must be tossed out of scientific, secular discourse, and be consigned to the arcane sphere of the divine studies. In consequence, the idea of a natural law founded on reason and rational inquiry has been virtually lost.
The believer in a rationally established natural law must, then, face the hostility of both camps: the one group sensing in this position an antagonism toward religion; and the other group suspecting that God and mysticism are being slipped in by the back door. To the first group, it must be said that they are reflecting an extreme Augustinian position which held that faith rather than reason was the only legitimate tool for investigating man's nature and man's proper ends. In short, in this fideist tradition, theology had completely displaced philosophy. The Thomist tradition, on the contrary, was precisely the opposite: vindicating the independence of philosophy from theology and proclaiming the ability of man's reason to understand and arrive at the laws, physical and ethical, of the natural order. If belief in a systematic order of natural laws open to discovery by man's reason is per se anti-religious, then anti-religious also were St. Thomas and the later Scholastics, as well as the devout Protestant jurist Hugo Grotius. The statement that there is an order of natural law, in short, leaves open the problem of whether or not God has created that order; and the assertion of the viability of man's reason to discover the natural order leaves open the question of whether or not that reason was given to man by God. The assertion of an order of natural laws discoverable by reason is, by itself, neither pro- nor anti-religious.
Because this position is startling to most people today let us investigate this Thomistic position a little further. The statement of absolute independence of natural law from the question of the existence of God was implicit rather than flatly asserted in St. Thomas himself; but like so many implications of Thomism, it was brought forth by Suarez and the other brilliant Spanish Scholastics of the late sixteenth century. The Jesuit Suarez pointed out that many Scholastics had taken the position that the natural law of ethics, the law of what is good and bad for man, does not depend upon God's will. Indeed, some of the Scholastics had gone so far as to say that:
"...even though God did not exist, or did not make use of His reason, or did not judge rightly of things, if there is in man such a dictate of right reason to guide him, it would have had the same nature of law as it now has."
Dutch Protestant jurist Hugo Grotius declared, in his De Iure Belli ac Pacis (1625):
"What we have been saying would have a degree of validity even if we should concede that which cannot be conceded without the utmost wickedness, that there is no God."
"Measureless as is the power of God, nevertheless it can be said that there are certain things over which that power does not extend. . . . Just as even God cannot cause that two times two should not make four, so He cannot cause that which is intrinsically evil be not evil."
[Maurizio Passerin] D'Entrèves concludes that:
"[Grotius’s] definition of natural law has nothing revolutionary. When he maintains that natural law is that body of rules which Man is able to discover by the use of his reason, he does nothing but restate the Scholastic notion of a rational foundation of ethics. Indeed, his aim is rather to restore that notion which had been shaken by the extreme Augustinianism of certain Protestant currents of thought. When he declares that these rules are valid in themselves, independently of the fact that God willed them, he repeats an assertion which had already been made by some of the schoolmen."
Grotius's aim, d'Entrèves adds, "was to construct a system of laws which would carry conviction in an age in which theological controversy was gradually losing the power to do so." Grotius and his juristic successors—--Pufendorf, Burlamaqui, and Vattel—--proceeded to elaborate this independent body of natural laws in a purely secular context, in accordance with their own particular interests, which were not, in contrast to the Schoolmen, primarily theological. Indeed, even the eighteenth-century rationalists, in many ways dedicated enemies of the Scholastics, were profoundly influenced in their very rationalism by the Scholastic tradition.
Thus, let there be no mistake: 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. Hence, St. Thomas Aquinas, in the words of the eminent historian of philosophy Father Copleston, "emphasized the place and function of reason in moral conduct. He [Aquinas] shared with Aristotle the view that it is the possession of reason which distinguished man from the animals" and which "enables him to act deliberately in view of the consciously apprehended end and raises him above the level of purely instinctive behavior."
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. For Aquinas, then, in the words of Copleston, "there is therefore room for the concept of 'right reason,' reason directing man's acts to the attainment of the objective good for man." Moral conduct is therefore conduct in accord with right reason: "If it is said that moral conduct is rational conduct, what is meant is that it is conduct in accordance with right reason, reason apprehending the objective good for man and dictating the means to its attainment."
In natural-law philosophy, then, reason is not bound, as it is in modern post-Humean philosophy, to be a mere slave to the passions, confined to cranking out the discovery of the means to arbitrarily chosen ends. For the ends themselves are selected by the use of reason; and "right reason” dictates to man his proper ends as well as the means for their attainment. For the Thomist or natural-law theorist, the general law of morality for man is a special case of the system of natural law governing all entities of the world, each with its own nature and its own ends. "For him the moral law . . . is a special case of the general principles that all finite things move toward their ends by the development of their potentialities." And here we come to a vital difference between inanimate or even non-human living creatures, and man himself; for the former are compelled to proceed in accordance with the ends dictated by their natures, whereas man, "the rational animal," possesses reason to discover such ends and the free will to choose.
Which doctrine, natural law or those of its critics, is to be considered truly rational was answered incisively by the late Leo Strauss, in the course of a penetrating critique of the value-relativism in political theory of Professor Arnold Brecht. For, in contrast to natural law,
"positivistic social science . . . is characterized by the abandonment of reason or the flight from reason. . .Finally, the unique place of reason in natural-law philosophy has been affirmed by the modern Thomistic philosopher, the late Father John Toohey. Toohey defined sound philosophy as follows: "Philosophy, in the sense in which the word is used when scholasticism is contrasted with other philosophies, is an attempt on the part of man's unaided reason to give a fundamental explanation of the nature of things."
According to the positivistic interpretation of relativism which prevails in present-day social science . . . reason can tell us which means are conducive to which ends; it cannot tell us which attainable ends are to be preferred to other attainable ends. Reason cannot tell us that we ought to choose attainable ends; if someone 'loves him who desires the impossible,' reason may tell him that he acts irrationally, but it cannot tell him that he ought to act rationally, or that acting irrationally is acting badly or basely. If rational conduct consists in choosing the right means for the right end, relativism teaches in effect that rational conduct is impossible.
[Ed.---What's interesting is that James Wilson, the key Founder who was second only to James Madison in the drafting of the Constitution, goes even further, tying natural law to "the will of God." Indeed, the Founders cheated a bit, roping God into what was a "natural" argument, not Bible but reason. If one reads James Wilson with Thomism in mind, it's clear that man's reason wasn't sitting on a shelf all those years, waiting for the Enlightenment to arrive.]