Mises Daily Articles
Introduction to Natural Law
1. Natural Law and Reason
Among intellectuals who consider themselves "scientific," the phrase "the nature of man" is 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.1
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.2
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.3 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.4
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.
Or, as a modern Thomist philosopher declares:
If the word "natural' means anything at all, it refers to the nature of a man, and when used with "law," "natural" must refer to an ordering that is manifested in the inclinations of a man's nature and to nothing else. Hence, taken in itself, there is nothing religious or theological in the "Natural Law" of Aquinas.
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.
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….
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.
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."
2. Natural Law as "Science"
It is indeed puzzling that so many modern philosophers should sniff at the very term "nature" as an injection of mysticism and the supernatural. An apple, let fall, will drop to the ground; this we all observe and acknowledge to be in the nature of the apple (as well as the world in general). Two atoms of hydrogen combined with one of oxygen will yield one molecule of water — behavior that is uniquely in the nature of hydrogen, oxygen, and water. There is nothing arcane or mystical about such observations. Why then cavil at the concept of "nature"? The world, in fact, consists of a myriad number of observable things, or entities. This is surely an observable fact. Since the world does not consist of one homogenous thing or entity alone, it follows that each one of these different things possesses differing attributes, otherwise they would all be the same thing. But if A, B, C, etc., have different attributes, it follows immediately that they have different natures. It also follows that when these various things meet and interact, a specifically delimitable and definable result will occur. In short, specific, delimitable causes will have specific delimitable effects.
The observable behavior of each of these entities is the law of their natures, and this law includes what happens as a result of the interactions. The complex that we may build up of these laws may be termed the structure of natural law. What is "mystical" about that?
In the field of purely physical laws, this concept will usually differ from modern positivistic terminology only on high philosophical levels; applied to man, however, the concept is far more controversial. And yet, if apples and stones and roses each have their specific natures, is man the only entity, the only being, that cannot have one? And if man does have a nature, why cannot it too be open to rational observation and reflection? If all things have natures, then surely man's nature is open to inspection; the current brusque rejection of the concept of the nature of man is therefore arbitrary and a priori.
One common, flip criticism by opponents of natural law is: who is to establish the alleged truths about man? The answer is not who but what: man's reason. Man's reason is objective, i.e., it can be employed by all men to yield truths about the world. To ask what is man's nature is to invite the answer. Go thou and study and find out! It is as if one man were to assert that the nature of copper were open to rational investigation and a critic were to challenge him to "prove" this immediately by setting forth on the spot all the laws that have been discovered about copper.
Another common charge is that natural-law theorists differ among themselves, and that therefore all natural-law theories must be discarded. This charge comes with peculiar ill grace when it comes, as it often does, from utilitarian economists. For economics has been a notoriously contentious science — and yet few people advocate tossing all economics therefore into the discard. Furthermore, difference of opinion is no excuse for discarding all sides to a dispute; the responsible person is the one who uses his reason to examine the various contentions and make up his own mind. He does not simply say a priori, "a plague on all your houses!" The fact of man's reason does not mean that error is impossible. Even such "hard" sciences as physics and chemistry have had their errors and their fervent disputes. No man is omniscient or infallible — a law, by the way, of man's nature.
The natural law ethic decrees that for all living things, "goodness" is the fulfillment of what is best for that type of creature; "goodness" is therefore relative to the nature of the creature concerned. Thus, Professor Cropsey writes:
The classical [natural law] doctrine is that each thing is excellent in the degree to which it can do the things for which its species is naturally equipped … Why is the natural good? … [Because] there is neither a way nor a reason to prevent ourselves from distinguishing between useless and serviceable beasts, for example; and … the most empirical and … rational standard of the serviceable, or the limit of the thing's activity is set by its nature. We do not judge elephants to be good because they are natural; or because nature is morally good — whatever that would mean. We judge a particular elephant to be good by the light of what elephant nature makes it possible for elephants to do and to be.
In the case of man, the natural-law ethic states that goodness or badness can be determined by what fulfills or thwarts what is best for man's nature.
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, contentual sense. As Father Kenealy put it:
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.
And the eminent English jurist, Sir William Blackstone, summed up the natural law and its relation to human happiness as follows:
This is the foundation of what we call ethics, or natural law … demonstrating that this or that action tends to man's real happiness, and therefore very justly concluding that the performance of it is a part of the law of nature; or, on the other hand, that this or that action is destruction of man's real happiness, and therefore that the law of nature forbids it.
Without using the terminology of natural law, psychologist Leonard Carmichael has indicated how an objective, absolute ethic can be established for man on scientific methods, based upon biological and psychological inquiry:
because man has an unchanging and an age-old, genetically determined anatomical, physiological, and psychological make-up, there is reason to believe that at least some of the "values" that he recognized as good or bad have been discovered or have emerged as human individuals have lived together for thousands of years in many societies. Is there any reason to suggest that these values, once identified and tested, may not be thought of as essentially fixed and unchanging? For example, the wanton murder of one adult by another for the purely personal amusement of the person committing the murder, once it is recognized as a general wrong, is likely always to be so recognized. Such a murder has disadvantageous individual and social effects. Or to take a milder example from esthetics, man is always likely to recognize in a special way the balance of two complementary colors because he is born with specially constituted human eyes.
One common philosophic objection to natural law ethics is that it confuses, or identifies, the realism of fact and value. For purposes of our brief discussion, John Wild's reply will suffice:
In answer we may point out that their [natural law] view identifies value not with existence but rather with the fulfillment of tendencies determined by the structure of the existent entity. Furthermore, it identifies evil not with non-existence but rather with a mode of existence in which natural tendencies are thwarted and deprived of realization…. The young plant whose leaves are withering for lack of light is not nonexistent. It exists, but in an unhealthy or privative mode. The lame man is not nonexistent. He exists, but with a natural power partially unrealized. … This metaphysical objection is based upon the common assumption that existence is fully finished or complete. … [But] what is good is the fulfillment of being.
After stating that ethics, for man as for any other entity, are determined by investigating verifiable existing tendencies of that entity, Wild asks a question crucial to all non-theological ethics: "why are such principles felt to be binding on me?" How do such universal tendencies of human nature become incorporated into a person's subjective value scale? Because
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.
David Hume is the philosopher supposed by modern philosophers to have effectively demolished the theory of natural law. Hume's "demolition" was two-pronged: the raising of the alleged "fact-value" dichotomy, thus debarring the inference of value from fact, and his view that reason is and can only be a slave to the passions.
In short, in contrast to the natural-law view that man's reason can discover the proper ends for man to follow, Hume held that only the emotions can ultimately set man's ends, and that reason's place is as the technician and handmaiden to the emotions. (Here Hume has been followed by modern social scientists since Max Weber.) According to this view, people's emotions are assumed to be primary and unanalyzable givens.
Professor Hesselberg has shown, however, that Hume, in the course of his own discussions, was compelled to reintroduce a natural-law conception into his social philosophy and particularly into his theory of justice, thus illustrating the gibe of Etienne Gilson: "The natural law always buries its undertakers." For Hume, in Hesselberg's words, "recognized and accepted that the social … order is an indispensable prerequisite to man's well-being and happiness: and that this is a statement of fact." The social order, therefore, must be maintained by man. Hesselberg continues:
But a social order is not possible unless man is able to conceive what it is, and what its advantages are, and also conceive those norms of conduct which are necessary to its establishment and preservation, namely, respect for another's person and for his rightful possessions, which is the substance of justice … But justice is the product of reason, not the passions. And justice is the necessary support of the social order; and the social order is necessary to man's well-being and happiness. If this is so, the norms of justice must control and regulate the passions, and not vice versa.
Hesselberg concludes that "thus Hume's original 'primacy of the passions' thesis is seen to be utterly untenable for his social and political theory, and … he is compelled to reintroduce reason as a cognitive-normative factor in human social relations."
Indeed, in discussing justice and the importance of the rights of private property, Hume was compelled to write that reason can establish such a social ethic: "nature provides a remedy in the judgment and understanding for what is irregular and uncommodious in the affections" — in short, reason can be superior to the passions.
We have seen from our discussion that the doctrine of natural law — the view that an objective ethics can be established through reason — has had to face two powerful groups of enemies in the modern world: both anxious to denigrate the power of man's reason to decide upon his destiny. These are the fideists who believe that ethics can only be given to man by supernatural revelation, and the skeptics who believe that man must take his ethics from arbitrary whim or emotion. We may sum up with Professor Grant's harsh but penetrating view of
the strange contemporary alliance between those who doubt the capacity of human reason in the name of scepticism (probably scientific in origin) and those who denigrate its capacity in the name of revealed religion. It is only necessary to study the thought of Ockham to see how ancient this strange alliance is. For in Ockham can be seen how philosophic nominalism, unable to face the question of practical certainty, solves it by the arbitrary hypothesis of revelation. The will detached from the intellect (as it must be in a nominalism) can seek certainty only through such arbitrary hypotheses.
The interesting fact historically is that these two anti-rationalist traditions — that of the liberal skeptic and the Protestant revelationist — should originally have come from two … opposite views of man. The Protestant dependence upon revelation arose from a great pessimism about human nature … The immediately apprehended values of the liberal originate in a great optimism. Yet … after all, is not the dominating tradition in North America a Protestantism which has been transformed by pragmatic technology and liberal aspirations?
3. Natural Law versus Positive Law
If, then, the natural law is discovered by reason from "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. The natural law is, in essence, a profoundly "radical" ethic, for it holds the existing status quo, which might grossly violate natural law, up to the unsparing and unyielding light of reason. In the realm of politics or State action, the natural law presents man with a set of norms which may well be radically critical of existing positive law imposed by the State. At this point, we need only stress that the very existence of a natural law discoverable by reason is a potentially powerful threat to the status quo and a standing reproach to the reign of blindly traditional custom or the arbitrary will of the State apparatus.
In fact, the legal principles of any society can be established in three alternate ways: (a) by following the traditional custom of the tribe or community; (b) by obeying the arbitrary, ad hoc will of those who rule the State apparatus; or (c) by the use of man's reason in discovering the natural law — in short, by slavish conformity to custom, by arbitrary whim, or by use of man's reason. These are essentially the only possible ways for establishing positive law. Here we may simply affirm that the latter method is at once the most appropriate for man at his most nobly and fully human, and the most potentially "revolutionary" vis-à-vis any given status quo.
In our century, widespread ignorance of and scorn for the very existence of the natural law has limited people's advocacy of legal structures to (a) or (b), or some blend of the two. This even holds for those who try to hew to a policy of individual liberty. Thus, there are those libertarians who would simply and uncritically adopt the common law, despite its many anti-libertarian flaws. Others, like Henry Hazlitt, would scrap all constitutional limitations on government to rely solely on the majority will as expressed by the legislature. Neither group seems to understand the concept of a structure of rational natural law to be used as a guidepost for shaping and reshaping whatever positive law may be in existence.
While natural-law theory has often been used erroneously in defense of the political status quo, its radical and "revolutionary" implications were brilliantly understood by the great Catholic libertarian historian Lord Acton. Acton saw clearly that the deep flaw in the ancient Greek — and their later followers' — conception of natural law political philosophy was to identify politics and morals, and then to place the supreme social moral agent in the State. From Plato and Aristotle, the State's proclaimed supremacy was founded in their view that "morality was undistinguished from religion and politics from morals; and in religion, morality, and politics there was only one legislator and one authority."
Acton added that the Stoics developed the correct, non-State principles of natural law political philosophy, which were then revived in the modern period by Grotius and his followers. "From that time it became possible to make politics a matter of principle and of conscience." The reaction of the State to this theoretical development was horror:
When Cumberland and Pufendorf unfolded the true significance of [Grotius's] doctrine, every settled authority, every triumphant interest recoiled aghast … It was manifest that all persons who had learned that political science is an affair of conscience rather than of might and expediency, must regard their adversaries as men without principle.
Acton saw clearly that any set of objective moral principles rooted in the nature of man must inevitably come into conflict with custom and with positive law. To Acton, such an irrepressible conflict was an essential attribute of classical liberalism: "Liberalism wishes for what ought to be, irrespective of what is." As Himmelfarb writes of Acton's philosophy:
the past was allowed no authority except as it happened to conform to morality. To take seriously this Liberal theory of history, to give precedence to "what ought to be" over "what is" was, he admitted, virtually to install a "revolution in permanence."
And so, for Acton, the individual, armed with natural law moral principles, is then in a firm position from which to criticize existing regimes and institutions, to hold them up to the strong and harsh light of reason. Even the far less politically oriented John Wild has trenchantly described the inherently radical nature of natural-law theory:
the philosophy of natural law defends the rational dignity of the human individual and his right and duty to criticize by word and deed any existent institution or social structure in terms of those universal moral principles which can be apprehended by the individual intellect alone.
If the very idea of natural law is essentially "radical" and deeply critical of existing political institutions, then how has natural law become generally classified as "conservative"? Professor Parthemos considers natural law to be "conservative" because its principles are universal, fixed, and immutable, and hence are "absolute" principles of justice. Very true — but how does fixity of principle imply "conservatism"? On the contrary, the fact that natural-law theorists derive from the very nature of man a fixed structure of law independent of time and place, or of habit or authority or group norms, makes that law a mighty force for radical change. The only exception would be the surely rare case where the positive law happens to coincide in every aspect with the natural law as discerned by human reason.
4. Natural Law and Natural Rights
As we have indicated, the great failing of natural-law theory — from Plato and Aristotle to the Thomists and down to Leo Strauss and his followers in the present day — is to have been profoundly statist rather than individualist. This "classical" natural-law theory placed the locus of the good and of virtuous action in the State, with individuals strictly subordinated to State action. Thus, from Aristotle's correct dictum that man is a "social animal," that his nature is best fitted for social cooperation, the classicists leaped illegitimately to a virtual identification of "society" and "the State," and thence to the State as the major locus of virtuous action. It was, in contrast, the Levellers and particularly John Locke in seventeenth-century England who transformed classical natural law into a theory grounded on methodological and hence political individualism. From the Lockean emphasis on the individual as the unit of action, as the entity who thinks, feels, chooses, and acts, stemmed his conception of natural law in politics as establishing the natural rights of each individual. It was the Lockean individualist tradition that profoundly influenced the later American revolutionaries and the dominant tradition of libertarian political thought in the revolutionary new nation. It is this tradition of natural-rights libertarianism upon which the present volume attempts to build.
Locke's celebrated "Second Treatise on Government" was certainly one of the first systematic elaborations of libertarian, individualistic, natural-rights theory. Indeed, the similarity between Locke' s view and the theory set forth below will become evident from the following passage:
[E]very man has a property in his own person. This nobody has any right to but himself. The labour of his body and the work of his hands, we may say, are properly his. Whatsoever then he removes out of the state that nature hath provided, and left it in, he hath mixed his labour with, and joined to it something that is his own, and thereby makes it his property. It being by him removed from the common state nature placed it in, it hath by this labour something annexed to it that excludes the common right of other men. For this labour being the unquestionable property of the labourer; no man but he can have a right to what that is once joined to….
He that is nourished by the acorns he picked up under an oak, or the apples he gathered from the trees in the wood, has certainly appropriated them to himself. Nobody can deny but the nourishment is his. I ask then when did they begin to be his? And 'tis plain, if the first gathering made them not his, nothing else could. That labour put a distinction between them and common. That added something to them more than nature, the common mother of all, had done: and so they become his private right. And will any one say he had no right to those acorns or apples he thus appropriated, because he had not the consent of all mankind to make them his? … If such a consent as that was necessary man had starved, notwithstanding the plenty God had given him. We see in commons, which remain so by compact, that 'tis the taking part of what is common, and removing it out of the state Nature leaves it in, which begins the property; without which the common is of no use.
It should not be surprising that Locke's natural-rights theory, as historians of political thought have shown, was riddled with contradictions and inconsistencies After all, the pioneers of any discipline, any science, are bound to suffer from inconsistencies and lacunae that will be corrected by those that come after them. Divergences from Locke in the present work are only surprising to those steeped in the unfortunate modern fashion that has virtually abolished constructive political philosophy in favor of a mere antiquarian interest in older texts. In fact, libertarian natural-rights theory continued to be expanded and purified after Locke, reaching its culmination in the nineteenth century works of Herbert Spencer and Lysander Spooner.
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. A few strikingly worded examples: nineteenth-century German-American theorist Francis Lieber, in his earlier and more libertarian treatise, wrote: "The law of nature or natural law … is the law, the body of rights, which we deduce from the essential nature of man." And the prominent nineteenth-century American Unitarian minister, William Ellery Channing: "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." And Theodore Woolsey, one of the last of the systematic natural rights theorists in nineteenth-century America: natural rights are those "which, by fair deduction from the present physical, moral, social, religious characteristics of man, he must be invested with … in order to fulfill the ends to which his nature calls him."
If, as we have seen, natural law is essentially a revolutionary theory, then so a fortiori is its individualist, natural-rights branch. As the nineteenth-century American natural-rights theorist Elisha P. Hurlbut put it:
The laws shall be merely declaratory of natural rights and natural wrongs, and … whatever is indifferent to the laws of nature shall be left unnoticed by human legislation … and legal tyranny arises whenever there is a departure from this simple principle.
A notable example of the revolutionary use of natural rights is, of course, the American Revolution, which was grounded in a radically revolutionary development of Lockean theory during the eighteenth century. The famous words of the Declaration of Independence, as Jefferson himself made clear, were enunciating nothing new, but were simply a brilliantly written distillation of the views held by the Americans of the day:
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness [the more common triad at the lime was "Life, Liberty and Property"]. That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed. That whenever any form of Government becomes destructive of these ends, it is the Right of the people to alter or to abolish it.
Particularly striking is the flaming prose of the great abolitionist William Lloyd Garrison, applying natural-rights theory in a revolutionary way to the question of slavery:
The right to enjoy liberty is inalienable. … Every man has a right to his own body — to the products of his own labor — to the protection of law. … That all these laws which are now in force, admitting the right of slavery are, therefore, before God, utterly null and void … and therefore they ought instantly to be abrogated.
We shall be speaking throughout this work of "rights," in particular the rights of individuals to property in their persons and in material objects. But how do we define "rights"? "Right" has cogently and trenchantly been defined by Professor Sadowsky:
When we say that one has the right to do certain things we mean this and only this, that it would be immoral for another, alone or in combination, to stop him from doing this by the use of physical force or the threat thereof. We do not mean that any use a man makes of his property within the limits set forth is necessarily a moral use.
Sadowsky's definition highlights the crucial distinction we shall make throughout this work between a man's right and the morality or immorality of his exercise of that right. We will contend that it is a man's right to do whatever he wishes with his person; it is his right not to be molested or interfered with by violence from exercising that right. But what may be the moral or immoral ways of exercising that right is a question of personal ethics rather than of political philosophy — which is concerned solely with matters of right, and of the proper or improper exercise of physical violence in human relations. The importance of this crucial distinction cannot be overemphasized. Or, as Elisha Hurlbut concisely put it: "The exercise of a faculty [by an individual] is its only use. The manner of its exercise is one thing; that involves a question of morals. The right to its exercise is another thing."
5. The Task of Political Philosophy
It is not the intention of this book to expound or defend at length the philosophy of natural law, or to elaborate a natural-law ethic for the personal morality of man. The intention is to set forth a social ethic of liberty i.e., to elaborate that subset of the natural law that develops the concept of natural rights, and that deals with the proper sphere of "politics," i.e., with violence and non-violence as modes of interpersonal relations. In short, to set forth a political philosophy of liberty.
In our view the major task of "political science" or better, "political philosophy" is to construct the edifice of natural law pertinent to the political scene. That this task has been almost completely neglected in this century by political scientists is all too clear. Political science has either pursued a positivistic and scientistic "model building," in vain imitation of the methodology and content of the physical sciences, or it has engaged in purely empirical fact-grubbing. The contemporary political scientist believes that he can avoid the necessity of moral judgments, and that he can help frame public policy without committing himself to any ethical position. And yet as soon as anyone makes any policy suggestion, however narrow or limited, an ethical judgment — sound or unsound — has willy-nilly been made.
The difference between the political scientist and the political philosopher is that the "scientist's" moral judgments are covert and implicit, and therefore not subject to detailed scrutiny, and hence more likely to be unsound. Moreover, the avoidance of explicit ethical judgments leads political scientists to one overriding implicit value judgment — that in favor of the political status quo as it happens to prevail in any given society. At the very least, his lack of a systematic political ethics precludes the political scientist from persuading anyone of the value of any change from the status quo.
In the meanwhile, furthermore, present-day political philosophers generally confine themselves, also in a Wertfrei manner, to antiquarian descriptions and exegeses of the views of other, long-gone political philosophers. In so doing, they are evading the major task of political philosophy, in the words of Thomas Thorson, "the philosophic justification of value positions relevant to politics."
In order to advocate public policy, therefore, a system of social or political ethics must be constructed. In former centuries this was the crucial task of political philosophy. But in the contemporary world, political theory, in the name of a spurious "science," has cast out ethical philosophy, and has itself become barren as a guide to the inquiring citizen. The same course has been taken in each of the disciplines of the social sciences and of philosophy by abandoning the procedures of natural law. Let us then cast out the hobgoblins of Wertfreiheit, of positivism, of scientism. Ignoring the imperious demands of an arbitrary status quo, let us hammer out — hackneyed cliché though it may be — a natural-law and natural-rights standard to which the wise and honest may repair. Specifically, let us seek to establish the political philosophy of liberty and of the proper sphere of law, property rights, and the State.
 From Franciscus Suarez, De Legibus ac Deo Legislatore (1619), lib. II, Cap. vi. Suarez also noted that many Scholastics "seem therefore logically to admit that natural law does not proceed from God as a lawgiver, for it is not dependent on God's will." Quoted in A.P. d'Enfreves, Natural Law (London: Hutchinson University Library, 1951), p. 71.
 Thomas E Davitt, S.J., "St. Thomas Aquinas and the Natural Law," in Arthur L. Harding, ed., Origins of the Natural Law Tradition (Dallas, Tex.: Southern Methodist University Press, 1954), p. 39. Also see Brendan F. Brown, ed., The Natural Law Reader (New York: Oceana Pubs., 1960), pp. 101–4.
 Quoted in d'Entrèves, Natural Law, pp. 52–53. See also Otto Gierke, Natural Law and the Theory of Society, 1500 to 1800 (Boston: Beacon Press, 1957), pp. 98–99.
 D'Entrèves, Natural Law, pp. 51–52. Also see A.H. Chroust, "Hugo Grotius and the Scholastic Natural Law Tradition," The New Scholasticism (1943), and Frederick C. Copleston, S.J., A History of Philosophy (Westminster, Md.: Newman Press, 1959), 2, pp. 330f. On the neglected influence of the Spanish Scholastic Suarez on modern philosophers, see Jose Ferrater Mora, "Suarez and Modern Philosophy," Journal of the History of Ideas (October 1953): 528–47.
 See Gierke, Natural Law and the Theory of Society, p. 289. Also see Herbert Spencer, An Autobiography (New York: D. Appleton, 1904), vol. 1, p. 415.
 Thus, see Carl L. Becker, The Heavenly City of the Eighteenth-century Philosophers (New Haven, Conn.: Yale University Press, 1957), p. 8.
 The late realist philosopher John Wild, in his important article, "Natural Law and Modern Ethical Theory," Ethics (October 1952), states:
Realistic [natural law] ethics is now often dismissed as theological and authoritarian in character. But this is a misunderstanding. Its ablest representatives, from Plato and Aristotle to Grotius, have defended it on the basis of empirical evidence alone without any appeal to supernatural authority (p. 2, and pp. 1–13).
Also see the denial of the existence of such a thing as "Christian philosophy" any more than "Christian hats and shoes" by the Catholic social philosopher Orestes Brownson. Thomas T. McAvoy, C.S.C., "Orestes A. Brownson and Archbishop John Hughes in 1860," Review of Politics (January 1962): 29.
 Frederick C. Copleston, S.J., Aquinas (London: Penguin Books, 1955), p. 204.
 Ibid., pp. 204–05.
 Ibid., p. 212.
 Thus Copleston:
Inanimate bodies act in certain ways precisely because they are what they are, and they cannot act otherwise; they cannot perform actions which are contrary to their nature. And animals are governed by instinct. In fine, all creatures below man participate unconsciously in the eternal law, which is reflected in their natural tendencies, and they do not possess the freedom which is required in order to be able to act in a mariner incompatible with this law. It is therefore essential that he [man] should know the eternal law in so far as it concerns himself. Yet, how can he know it? He cannot read, as it were, the mind of God… [but] he can discern the fundamental tendencies and needs of his nature, and by reflecting on them he can come to a knowledge of the natural moral law…. Every man possesses … the light of reason whereby he can reflect … and promulgate to himself the natural law, which is the totality of the universal precepts or dictates of right reason concerning the good which is to be pursued and the evil which is to be shunned (Ibid., pp. 213–14).
 Leo Strauss, "Relativism," in H. Schoeck and J. W. Wiggins, eds., Relativism and the Study of Man (Princeton, NJ.: D. Van Nostrand, 1961), pp. 144–45. For a devastating critique of an attempt by a relativistic political scientist to present a "value-free" case for freedom and the self-development of the person, see Walter Berns, "The Behavioral Sciences and the Study of Political Things: The Case of Christian Bay's The Structure of Freedom," American Political Science Review (September 1961): 550–59.
 Toohey adds that "scholastic philosophy is the philosophy which teaches the certitude of human knowledge acquired by means of sense experience, testimony, reflection, and reasoning." John J. Toohey, S.J., Notes on Epistemology (Washington, D.C.: Georgetown University, 1952), pp. 111–12.
 Henry B. Veatch, in his For an Ontology of Morals: A Critique of Contemporary Ethical Theory (Evanston, Ill.: Northwestern University Press, 1971), p. 7, states:
Recourse must be had to an older notion than that which has now come to be in fashion among contemporary scientists and philosophers of science…. Surely, in that everyday world of common-sense existence in which, as human beings, and for all of cur scientific sophistication, we can hardly cease to live and move and have our being, we do indeed find ourselves constantly invoking an older and even a decidedly common sense notion of "nature" and "natural law." For don't we all recognize that a rose is different from an eggplant, and a man from a mouse, and hydrogen from manganese? To recognize such differences in things is surely to recognize that they behave differently: one doesn't expect of a man quite the same things that one does of a mouse, and vice versa. Moreover, the reason our expectations thus differ as to what various types of things or entities will do, or how they will act and react, is simply that they just are different kinds of things. They have different "natures," as one might say, using the old-fashioned terminology.
Leo Strauss (Natural Right and History [Chicago: University of Chicago Press, 1953]) adds:
Socrates deviated from his predecessors by identifying the science of … everything that is, with the understanding of what each of the beings is. For "to be" means "to be something" and hence to be different from things which are "something else": "to be" means therefore "to be a part" (p. 122).
 For a defense of the concept of nature, see Alvin Plantinga, The Nature of Necessity (Oxford: Clarendon Press, 1974), pp. 71–81.
 See H.W.B. Joseph, An Introduction to Logic, 2nd rev. ed (Oxford: Clarendon Press, 1916), pp. 407–9. For a hard-hitting defense of the view that causation states a necessary relation among entities, see R. Harre and E. H. Madden, Causal Powers: A Theory of Natural Necessity (Totowa, N.J.: Rowman and Littlefield, 1975).
 See Murray N. Rothbard, Individualism and the Philosophy of the Social Sciences (San Francisco: Cato Institute, 1979), p. 5.
 And there is a further point: the very existence of a difference of opinion seems to imply that there is something objective about which disagreement can take place; for otherwise, there would be no contradictions in the different "opinions" and no worry about these conflicts. For a similar argument in refutation of moral subjectivism see G.E. Moore, Ethics (Oxford, 1963 [1912)), pp. 63ff.
 The psychologist Leonard Carmichael, in "Absolutes, Relativism and the Scientific Psychology of Human Nature," in H. Schoeck and J. Wiggins, eds., Relativism and the Study of Man (Princeton, N.J.: 1). Van Nostrand, 1961), p. 16, writes:
We do not turn aside from what we know about astronomy at any time because there is a great deal we do not know, or because so much that we once thought we knew is no longer recognized as true. May not the same argument be accepted in our thinking about ethical and esthetic judgments?
 Joseph Cropsey, "A Reply to Rothman," American Political Science Review (June 1962): 355. As Henry Veatch writes, in For an Ontology of Morals, pp. 7–8:
Moreover, it is in virtue of a thing's nature — i.e., of its being the kind of thing that it is — that it acts and behaves the way it does. Is it not also in virtue of a thing's nature that we often consider ourselves able to judge what that thing might or could be, but perhaps isn't? A plant, for example, may be seen to be underdeveloped or stunted in its growth. A bird with an injured wing is quite obviously not able to fly as well as others of the same species…. And so it is that a thing's nature maybe thought of as being not merely that in virtue of which the thing acts or behaves in the way it does, but also as a sort of standard in terms of which we judge whether the thing's action or behavior is all that it might have been or could have been.
 For a similar approach to the meaning of goodness, see Peter Geach, "Good and Evil," in Philippa R. Foot, ed., Theories of Ethics (London: Oxford University Press, 1967), pp. 74–82.
 Contrast John Wild, in "Natural Law and Modern Ethical Theory," Ethics (October 1952): 2, who says:
Realistic ethics is founded on the basic distinction between human need and uncriticized individual desire or pleasure, a distinction not found in modern utilitarianism. The basic concepts of so-called "naturalistic" theories are psychological whereas those of realism are existential and ontological.
 William J. Kenealy, S.J., "The Majesty of the Law," Loyola Law Review (1949–50): 112–13; reprinted in Brendan F.Brown, ed., The Natural Law Reader (NewYork: Oceana, 1960), p. 123.
 Blackstone, Commentaries on the Laws of England, Book 1: quoted in Brown, Natural Law Reader, p. 106.
 Carmichael, "Absolutes," p.9.
 Wild, "Natural Law," pp. 4–5. Wild continues on p.11:
Existence is … not a property but a structuralized activity. Such activities are a kind of fact. They can be observed and described by judgments that are true or false: human life needs material artifacts; technological endeavors need rational guidance; the child has cognitive faculties that need education. Value statements are founded on the directly verifiable fact of tendency or need. The value or realization is required not merely by us but by the existent tendency for its completion. From a sound description and analysis of the given tendency we can infer the value founded upon it This is why we do not say that moral principles are mere statements of fact, but rather that they are "founded" on facts.
On pp. 2–4, Wild says:
The ethics of natural law … recognizes prescriptive moral laws but asserts that these are founded on tendential facts which may be described…. Goodness … must … be conceived dynamically as an existential mode, the realization of natural tendency. In this view, the world is not made up of determinate structures alone, but of determinate structures in an act of existing which they determine toward further appropriate acts of existing…. No determinate structure cart be given existence without determining active tendencies. When such a tendency is fulfilled in accordance with natural law, the entity is said to be in a stable, healthy, or sound condition — adjectives of value. When it is obstructed or distorted, the entity is said to be in an unstable, diseased or unsound condition — adjectives of disvalue. Goodness and badness in their ontological sense are not phases of abstract structure, but rather modes of existence, ways in which the existential tendencies determined by such structures are either fulfilled or barely sustained in a deprived, distorted state.
 Ibid., p. 12. For more on a defense of natural law ethics, see John Wild, Plato's Modern Enemies and the Theory of Natural Law (Chicago: University of Chicago Press, 1953); Henry Veatch, Rational Man: A Modern Interpretation of Aristotelian Ethics (Bloomington: University of Indiana Press, 1962); and Veatch, For An Ontology of Morals.
 Hume in fact failed to prove that values cannot be derived from facts. It is frequently alleged that nothing can be in the conclusion of an argument which was not in one of the premises; and that therefore, an "ought" conclusion cannot follow from descriptive premises. But a conclusion follows from both premises taken together; the "ought" need not be present in either one of the premises so long as it has been validly deduced. To say that it cannot be so deduced simply begs the question. See Philippa R. Foot, Virtues and Vices (Berkeley: University of California Press, 1978), pp. 99–105.
 A. Kenneth Hesselberg, "Hume, Natural Law and Justice," Duquesne Review (Spring 1961): 46–47.
 David Hume, A Treatise of Human Nature, quoted in Hesselberg, "Hume, Natural Law, and Justice," p. 61. Hesselberg adds perceptively that Hume's sharp ought-is dichotomy in the earlier chapters of Hume's Treatise stemmed from his restricting the meaning of "reason" to finding pleasure — pain objects, and determining the means to achieve them. But, in the later chapters on justice, the very nature of the concept compelled Hume "to assign a third role to reason, namely its power to judge actions in terms of their suitability, or conformity or disconformity, to man's social nature, and thus paved the way for the return to a natural law concept of justice." Ibid., pp. 61–62.
For some doubt whether or not Hume himself intended to assert the fact-value dichotomy, see A.C. MacIntyre, "Hume on 'Is' and 'Ought," in W.D. Hudson, ed., The Is-Ought Question (London: Macmillan, 1969), pp. 35–50.
 George P. Grant, "Plato and Popper," The Canadian Journal of Economics and Political Science (May 1954): 191–92.
 Edwin W. Patterson, Jurisprudence Men and Ideas of the Law (Brooklyn, N.Y.: Foundation Press, 1953), p. 333.
 Hazlitt's reaction to my own brief discussion of the legal norms essential to any free-market economy [in Man, Economy, and State: A Treatise on Economic Principles (Princeton, N.J.: D. Van Nostrand, 1962] was a curious one. While critical of blind adherence to common law in other writers, Hazlitt could only react in puzzlement to my approach; calling it "abstract doctrinaire logic" and "extreme a priorism," he chided me for "trying to substitute his own instant jurisprudence for the common law principles built up through generations of human experience." It is curious that Hazlitt feels common law to be inferior to arbitrary majority will, and yet to be superior to human reason! Henry Hazlitt, "The Economics of Freedom," National Review (September 25, 1962): 232.
 John Edward Emerich Dalberg-Acton, Essays on Freedom and Power (Glencoe, Ill.: Free Press, 1948), p. 45. Also see Gertrude Himmelfarb, Lord Acton: A Study in Conscience and Politics (Chicago: University of Chicago Press, 1962), p. 135.
 Acton, Essays, p. 74. Himmelfarb correctly noted that "for Acton, politics was a science, the application of the principles of morality." Gertrude Himmelfarb, "Introduction," ibid., p. xxxvii
 Himmelfarb, Lord Acton, p. 204. Contrast the exclamation of bewilderment and horror by the leading nineteenth-century German Conservative, Adam Muller: "A natural law which differs from the positive law!" See Robert W. Lougee, "German Romanticism and Political Thought," Review of Politics (October 1959): 637.
 Himmelfarb, Lord Acton, p. 205.
 John Wild, Plato's Modern Enemies and the Theory of Natural Law (Chicago: University of Chicago Press, 1953), p. 176. Note the similar assessment by the conservative Otto Gierke, in Natural Law and the Theory of Society, 1500 to 1800 (Boston: Beacon Press, 1957), pp. 35–36, who was for that reason hostile to natural law:
In opposition to positive jurisprudence which still continued to show a Conservative trend, the natural-law theory of the State was Radical to the very core of its being … It was also directed… not to the purpose of scientific explanation of the past, but to… the exposition and justification of a new future which was to be called into existence.
 George S. Parthemos, "Contemporary Juristic Theory, Civil Rights, and American
Politics," Annals of the American Academy of Political and Social Science (November 1962): 101–2.
 The conservative political scientist Samuel Huntington recognizes the rarity of this event:
No ideational theory can be used to defend existing institutions satisfactorily, even when those institutions in general reflect the values of that ideology. The perfect nature of the ideology's ideal and the imperfect nature and inevitable mutation of the institutions create a gap between the two. The ideal becomes a standard by which to criticize the institutions, much to the embarrassment of those who believe in the ideal and yet still wish to defend the institutions.
Huntington then adds the footnote: "Hence any theory of natural law as a set of transcendent and universal moral principles is inherently non-conservative…. Opposition to natural law [is] … a distinguishing characteristic of conservatism." Samuel P. Huntington "Conservatism as an Ideology," American Political Science Review (June 1957): 458–59. See also Murray N. Rothbard, "Huntington on Conservatism: A Comment," American Political Science Review (September 1957): 784–87.
 For a critique of such typical confusion by a modern Thomist, see Murray N. Rothbard, Power and Market, 2nd ed. (Kansas City: Sheed Andrews and McMeel, 1977), pp. 237–38. Leo Strauss's defense of classical natural law and his assault on individualistic natural-rights theory may be found in his Natural Rights and History (Chicago: University of Chicago Press, 1953).
 John Locke, An Essay Concerning the True Origin, Extent, and End of Civil Government, V. pp.27–28, in Two Treatises of Government, P. Laslett, ed. (Cambridge: Cambridge University Press, 1960), pp. 305–7.
 Current scholars, ranging from Marxists to Straussians consider Thomas Hobbes rather than Locke as the founder of systematic individualist, natural rights theory. For a refutation of this view and a vindication of the older view of Hobbes as a statist and a totalitarian see Williamson M. Evers, "Hobbes and Liberalism," The Libertarian Forum (May 1975): 4–6 [available in PDF]. Also see Evers, "Social Contract: A Critique," The Journal of Libertarian Studies 1 (Summer 1977): 187–88 [available in PDF]. For a stress upon Hobbes's absolutism by a pro-Hobbesian German political theorist, see Carl Schmitt, Der Leviathan in der Staatslehre Thomas Hobbes (Hamburg, 1938). Schmitt was for a time a pro-Nazi theorist.
 Francis Lieber, Manual of Political Ethics (1838); Theodore Woolsey, Political Science (1877); cited in Benjamin F. Wright, Jr., American Interpretations of Natural Law (Cambridge, Mass.: Harvard University Press, 1931), pp. 261ff., 255ff., 276ff. William Ellery Channing, Works (Boston: American Unitarian Association, 1895), p. 693.
 Elisha P. Hurlbut, Essays on Human Rights and Their Political Guarantees (1845), cited in Wright, American Interpretations, pp. 257 ff.
 See Bernard Bailyn, The Ideological Origins of the American Revolution (Cambridge, Mass.: Belknap Press of Harvard University Press, 1967).
 William Lloyd Garrison, "Declaration of Sentiments of the American Anti-Slavery Convention" (December 1833), cited in W. and J. Pease, eds., The Antislavery Argument (Indianapolis: Bobbs-Merrill, 1965).
 James A. Sadowsky, S.J., "Private Property and Collective Ownership," in Tibor Machan, ed., The Libertarian Alternative (Chicago: Nelson-Hall, 1974), pp. 120–21.
 Hurlbut, cited in Wright, American Interpretations, pp. 257 ff.
 Cf. W. Zajdlic, "The Limitations of Social Sciences," Kyklos 9 (1956): 68–71.
 Hence, as Thorson points out, political philosophy is a subdivision of the philosophy of ethics, in contrast to "political theory" as well as positivistic analytic philosophy. See Thomas Landon Thorson, "Political Values and Analytic Philosophy," Journal of Politics (November 1961): 712n. Perhaps Professor Holton is right that "the decline in political philosophy is one part of a general decline," not only in philosophy itself, but also "in the status of rationality and ideas as such." Holton goes on to add that the two major challenges to genuine political philosophy in recent decades have come from historicism — the view that all ideas and truths are relative to particular historical conditions — and scientism, the imitation of the physical sciences. James Holton, "Is Political Philosophy Dead?" Western Political Quarterly (September 1961): 75ff.
- 1. The political theorist was the late Hannah Arendt. For a typical criticism of natural law by a legal Positivist, see Hans Kelsen, General Theory of Law and State (New York: Russell and Russell, 1961), pp. 8ff.
- 2. And yet, Black's Law Dictionary defines the natural law in a purely rationalistic and non-theological manner:
Jus Naturale, the natural law, or law of nature; law, or legal principles, supposed to be discoverable by the light of nature or abstract reasoning, or to be taught by nature to all nations and men alike, or law supposed to govern men and peoples in a state of nature, i.e., in advance of organized governments or enacted laws (3rd ed., p. 1044).
Professor Patterson, in Jurisprudence: Men and Ideas of the Law (Brooklyn: Foundation Press, 1953), p. 333, defines the natural law cogently and concisely as:
Principles of human conduct that are discoverable by "reason" from the basic inclinations of human nature, and that are absolute, immutable and of universal validity for all times and places. This is the basic conception of scholastic natural law … and most natural law philosophers.
- 3. Supporters of theological ethics nowadays typically strongly oppose the concept of natural law. See the discussion of casuistry by the neo-orthodox Protestant theologian Karl Barth, Church Dogmatics 3, 4 (Edinburgh: 11 and T. Clark, 1961), pp. 7ff.
- 4. For a discussion of the role of reason in the philosophy of Aquinas, see Etienne Gilson, The Christian Philosophy of St. Thomas Aquinas (New York: Random House, 1956). An important analysis of Thomistic natural law theory is Germain Grisez, "The First Principle of Practical Reason," in Anthony Kenny, ed., Aquinas: A Collection of Critical Essays (New York: Anchor Books, 1969), pp. 340–82. For a history of medieval natural law, see Odon Lottin, Psychologie et morale aux xiie et xiiie siècles, 6 vols. (Louvain, 1942–1960).