Lex Naturalis: A History of ‘Natural Law’ Philosophy
Natural law theory attempts to define a “higher law” on the foundation of a universal understanding of “good” and “evil”.
Curated/Reviewed by Matthew A. McIntosh
Natural law or the law of nature (Latin lex naturalis) is law whose content derives naturally from human nature or physical nature, and therefore has universal validity. In natural law jurisprudence, the content of man-made positive law is related to natural law, and gets its authority at least in part from its conformity to objective moral standards. Natural law theory attempts to define a “higher law” on the foundation of a universal understanding that certain choices in human life are good or evil, or that certain human actions are right or wrong.
Though Aristotle is often referred to as “the father of natural law,” this appellation is debatable and arises primarily from the interpretations of Thomas Aquinas. The Stoics asserted that the universe existed according to a rational and purposeful order (a divine or eternal law), and that the means by which a rational being lived in accordance with this order was the natural law, which dictated actions that accorded with virtue. Some of the early Church Fathers sought to incorporate this concept of natural law into Christianity. Thomas Hobbes defined natural law as the way in which a rational human being, seeking to survive and prosper in society, would act. Natural law theories influenced the development of English common law, and featured in the philosophies of Thomas Aquinas, Francisco Suárez, Thomas Hobbes, Hugo Grotius, Samuel von Pufendorf, and John Locke. The concept of natural rights was incorporated in the United States Declaration of Independence.
Definition of Natural Law
Natural law or the law of nature (Latin lex naturalis) is law whose content derives naturally from human nature or physical nature, and therefore has universal validity.  The term “natural law” is sometimes used as a contrast to the positive law of a given political community, society, or nation-state, and can be used as a standard by which to evaluate that law. In natural law jurisprudence, the content of positive law is related to natural law (or something like it), and gets its authority at least in part from its conformity to objective moral standards.
Natural law theory attempts to define a “higher law” on the foundation of a general understanding that certain choices in human life are good or evil, or that certain human actions are right or wrong. In ethical theory, certain choices, actions or dispositions might be asserted to be inhuman, unnaturally cruel, perverse, or unreasonable from a moral point of view. In political theory, certain proposals, policies or actions might be construed as violations of “human rights.” In international jurisprudence, certain actions might be defined as “crimes against humanity,” and nations or individuals might claim immunity from legal liability or obligations.
Natural law theory consists of propositions identifying certain types of choices, dispositions or actions as either right or wrong, and of statements explaining the objectivity of these propositions and the logic by which they are derived. The term “natural law” can be used synonymously with “natural justice” or “natural right” (Latin ius naturale), although most contemporary political and legal theorists separate the two.
Natural law theories have exercised a profound influence on the development of English common law, and have featured greatly in the philosophies of Thomas Aquinas, Francisco Suárez, Thomas Hobbes, Hugo Grotius, Samuel von Pufendorf, and John Locke. The concept of natural rights was incorporated in the United States “Declaration of Independence.”
The role and interpretation of natural law has varied widely through its history. There are a number of different theories of natural law, employing different conceptions of the role of morality in determining the authority of legal norms.
Greek philosophy emphasized the distinction between “nature” (physis, φúσις) and man-made “law,” “custom,” or “convention” (nomos,νóμος). What was commanded by law and custom varied from place to place, but what was dictated “by nature” was universally the same. To the Greeks, the term “law of nature” therefore appeared to be a paradox rather than something that obviously existed. Socrates and his philosophic heirs, Plato and Aristotle, posited the existence of “natural justice” or “natural right” (dikaion physikon,δικαιον φυσικον, Latin ius naturale), consisting of those expectations which, when human nature was taken into consideration, seemed reasonable for human beings co-existing in a society.
Aristotle is often referred to as “the father of natural law,” but this appellation is debatable. Aristotle emphasized the virtues, which he considered to be universal and a higher way of life. Aristotle’s association with natural law is due largely to the interpretation given to his works by Thomas Aquinas. and was based on Aquinas’ conflation of natural law and the “natural right” posited by Aristotle in Book V of the Nicomachean Ethics (= Book IV of the Eudemian Ethics). Aquinas’ influence affected a number of early translations of these passages, though more recent translations render them more literally. Aristotle noted that natural justice is a species of political justice, such as the scheme of distributive and corrective justice that would be established under the best political community; Were this scheme to take the form of law, it could be called a natural law, though Aristotle did not discuss this and suggests in Politics that the best regime may not rule by law at all.
The best evidence that Aristotle thought a natural law existed comes from Rhetoric, where Aristotle notes that, aside from the “particular” laws that each people has set up for itself, there is a “common” law that operates according to nature. The context of this remark, however, suggests only that Aristotle advised that there might be occasions where it could be rhetorically advantageous to appeal to such a law, especially when the “particular” law of one’s own city was averse to the case being made; he did not assert that there actually was such a law. Aristotle, moreover, considered two of the three candidates for a universally valid, natural law provided in this passage to be wrong.
Stoic Natural Law
The development of this tradition of “natural justice” into one of “natural law” is usually attributed to the Stoics. Whereas the “higher” law to which Aristotle suggested one could appeal arose directly from nature (as opposed to being the result of divine positive legislation), the Stoic concept of natural law was indifferent to its source. The Stoics asserted that the universe existed according to a rational and purposeful order (a divine or eternal law), and that the means by which a rational being lived in accordance with this order was the natural law, which dictated actions that accorded with virtue. These theories became highly influential among Roman jurists, and played an important role in subsequent legal theory.
Christian Natural Law
Despite the pagan origins of natural law theory, a number (though not all) of the early Church Fathers sought to incorporate it into Christianity, particularly in the West. Augustine of Hippo equated natural law with the state of man before the Fall; the implication was that after the Fall, life according to nature was no longer possible and men needed instead to seek salvation through divine law and grace. In the twelfth century, canon jurist Gratian reversed this, equating the natural and divine law. Thomas Aquinas restored the concept of natural law as something independent, asserting that, as the perfection of human reason, natural law could approach—but not fully comprehend—the eternal law and needed to be supplemented by divine law.
All human laws were to be judged by their conformity to natural law. An unjust law, which did not conform to natural law, was in a sense not a law at all. Natural law was not only used to judge the moral worth of various man-made laws, but also to determine what those laws said in the first place.
the rule and measure of human acts is the reason, which is the first principle of human acts. (Aquinas, ST I-II, Q. 90, A.I.)
Aquinas asserted that moral law derived from the nature of human beings, and that it was appropriate for them to behave in a way that corresponded to their rational nature.
Natural law was inherently teleological in its preoccupation with bringing about human happiness; its content was therefore determined by a conception of what elements, whether earthly satisfactions or spiritual fulfillment, constituted happiness. The state, in being bound by natural law, was conceived of as an institution which should be directed at realizing the true happiness of its citizens. This included directing its citizens to behave in a way that would ensure their spiritual salvation. In the sixteenth century, the School of Salamanca (Francisco Suárez, Francisco de Vitoria, and their contemporaries) further developed a philosophy of natural law. After the Church of England broke from Rome, the English theologian Richard Hooker adapted Thomistic notions of natural law to Anglicanism.
Natural Law of Hobbes
By the seventeenth century, the medieval teleological view had come under intense criticism from some quarters. Thomas Hobbes instead founded a social contractualist theory of legal positivism. He declared that all men could agree that what they sought (happiness) was subject to contention, but that a broad consensus could form around what they feared (violent death at the hands of another, and loss of liberty and personal property). Natural law was defined as the way in which a rational human being, seeking to survive and prosper, would act. It could be discovered by considering humankind’s natural rights; previous interpretations had derived natural rights by considering the natural law. In Hobbes’ opinion, the only way that natural law could prevail was by all men submitting to the commands of a sovereign. The ultimate source of law now became the sovereign, who was responsible for creating and enforcing laws to govern the behavior of his subjects. Since the sovereign’s decisions need not be grounded in morality, the result was legal positivism, the concept that law was created by the state and must therefore be obeyed by the citizens belonging to that state. Jeremy Bentham further developed the theory by modifying the concept of legal positivism.
In Thomas Hobbes’s treatise Leviathan, natural law is a precept, or general rule, discovered through reason, by which a man is forbidden to do anything which is destructive of his life, or takes away the means of preserving his life; and forbidden to omit doing anything which he thinks may preserve his life.
Hobbes defines nine Laws of Nature. The first two are expounded in chapter XIV (“of the first and second natural laws; and of contracts”); the others in chapter XV (“of other laws of nature”):
- “Every man ought to endeavour peace, as far as he has hope of obtaining it; and when he cannot obtain it, that he may seek and use all helps and advantages of war.”
- “A man [must] be willing, when others are so too, as far forth, as for peace, and defence of himself he shall think it necessary, to lay down this right to all things; and be contented with so much liberty against other men, as he would allow other men against himself.”
- “Men [must] perform their covenants made. In this law of nature consisteth the fountain and original of justice… when a covenant is made, then to break it is unjust and the definition of injustice is no other than the not performance of covenant. And whatsoever is not unjust is just.”
- “A man which receiveth benefit from another of mere grace, [must] endeavour that he which giveth it, have no reasonable cause to repent him of his good will.” Breach of this law is called ingratitude.
- Complaisance: “that every man strive to accommodate himself to the rest.” The observers of this law may be called sociable; the contrary, stubborn, insociable, forward, intractable.
- “Upon caution of the future time, a man ought to pardon the offences past of them that repenting, desire it.”
- “In revenges, men [must] look not at the greatness of the evil past, but the greatness of the good to follow.”
- “No man by deed, word, countenance, or gesture, [must] declare hatred or contempt of another,” the breach of which law is commonly called contumely (insulting and humiliating treatment).
- “Every man [must] acknowledge another for his equal by nature.” The breach of this precept is pride.
Liberal Natural Law
Liberal natural law grew out of both the medieval Christian natural law theories and out of Hobbes’ revision of natural law.
Hugo Grotius based his philosophy of international law on natural law. In particular, his writings on freedom of the seas and just war theory directly appealed to natural law. About natural law itself, he wrote that “even the will of an omnipotent being cannot change or abrogate” natural law, which “would maintain its objective validity even if we should assume the impossible, that there is no God or that he does not care for human affairs.” (De iure belli ac pacis, Prolegomeni XI). This famous argument etiamsi daremus (non esse Deum),made natural law no longer dependent on theology.
John Locke incorporated natural law into many of his theories, especially in Two Treatises of Government. There is considerable debate about whether his conception of natural law was more similar to that of Aquinas (filtered through Richard Hooker) or to Hobbes’ radical reinterpretation. Locke’s understanding is usually expressed as a revision of Hobbes’ definition of the social contract between a sovereign and the people of his state. Locke turned Hobbes’ prescription around, saying that if the ruler went against natural law and failed to protect “life, liberty, and property,” the people could justifiably overthrow the existing state and create a new one.
While Locke spoke in the language of natural law, the content of this law was largely protective of natural rights, and this was the language preferred by later liberal thinkers. Thomas Jefferson, echoing Locke, appealed to unalienable rights in the United States Declaration of Independence: “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.”
Contemporary Catholic Understanding
The Roman Catholic Church continues to hold the view of natural law set forth by Thomas Aquinas, particularly in his Summa Theologiae, and often as interpreted by the School of Salamanca. This view is also shared by some Protestant denominations.
They understand human beings to consist of body and mind, the physical and the non-physical (or soul), inextricably linked. Humans are capable of discerning the difference between good and evil because they have a conscience, and can pursue many manifestations of goodness. Some of these, such as procreation, are common to other animals, while others, like the pursuit of truth, are inclinations peculiar to the capacities of human beings.
To know what is right, one must use one’s reason and apply it to Aquinas’ precepts. The most important is the primary precept, self-preservation. There are also four subsidiary precepts: procreation, education of children, living in society, and worshipping God. In addition to these, there are secondary precepts, which Aquinas did not specify, and which are therefore open to interpretation and flexibility. Any rule that helps man to live up to the primary or subsidiary precepts can be a secondary precept, for example:
- Drunkenness is wrong because it injures one’s health, and worse, destroys one’s ability to reason, which is fundamental to man as a rational animal (in other words, it does not support self preservation).
- Theft is wrong because it destroys social relations, and man is by nature a social animal (therefore it does not support the subsidiary precept of living in society).
Natural moral law is concerned with both external and internal acts, also known as action and motive. In order to be truly moral, a person’s motive as well as his actions must be right. The motive must coincide with Aquinas’s cardinal or theological virtues. The cardinal virtues, which are acquired through reason applied to nature, are prudence, justice, fortitude and temperance. The theological virtues are hope, charity and faith.
According to Aquinas, to lack any of these virtues is to lack the ability to act morally. For example, a man who possesses the virtues of justice, prudence, and fortitude, yet lacks temperance, will find himself deviating from the moral path, despite his good intentions, due to his lack of self control and desire for pleasure.
In Contemporary Jurisprudence
In jurisprudence, natural law has a number of different meanings. It can refer to the doctrine a) that just laws are immanent in nature and can be “discovered” or “found” but not “created” by such exercises as a bill of rights; b) that they can emerge during the natural process of resolving conflicts, as embodied by the evolutionary process of the common law; or c) that the meaning of law is such that its content cannot be determined except by reference to moral principles. These meanings can either oppose or complement each other, although they share the concept that natural laws are inherent and not designed by man.
Legal positivism would say that an unjust law is nevertheless a law; natural law jurisprudence would say that an unjust law is legally deficient. Legal interpretivism—defended in the English-speaking world by Ronald Dworkin—claims to have a position different from both natural law and positivism.
The concept of natural law was important in the development of the English common law. In the struggles between Parliament and the British monarch, Parliament often made reference to the Fundamental Laws of England, which were at times declared to have embodied principles of natural law since time immemorial, and to set limits on the power of the monarchy. William Blackstone, however, declared that while natural law might be useful in determining the content of the common law and in deciding cases of equity, it was not itself identical with the Laws of England. The implication of natural law in the tradition of common law has meant that opponents of natural law and advocates of legal positivism, like Jeremy Bentham have also been staunch critics of the common law.
Natural law jurisprudence is currently undergoing a period of reformulation (as is legal positivism). The most prominent contemporary natural law jurist, Australian John Finnis (based in Oxford), Americans Germain Grisez and Robert P. George, and Canadian Joseph Boyle have all tried to construct a new version of natural law. The nineteenth-century anarchist and legal theorist, Lysander Spooner, was also a figure in the expression of modern natural law.
“New Natural Law” as it is sometimes called, which originated with Grisez, focuses on “basic human goods,” such as human life, which are “self-evidently” and intrinsically worthwhile, and states that these goods reveal themselves as being incommensurable with one another.
- Max Salomon Shellens, “Aristotle on Natural Law,” Natural Law Forum 4(1) (1959): 72–100
- William Blackstone, Commentaries on the Laws of England (1765), 9
- David L. Sills (ed.) “Natural Law” International Encyclopedia of the Social Sciences (New York: 1968)
- Blackstone, op. cit.
- Harry V. Jaffa, Thomism and Aristotelianism (Chicago: University of Chicago Press, 1952)
- H. Rackham, trans., Nicomachean Ethics (Loeb Classical Library); J. A. K. Thomson, trans. (revised by Hugh Tedennick), Nicomachean Ethics. (Penguin Classics).
- Joe Sachs, trans., Aristotle’s Nicomachean Ethics. (Focus Publishing/R. Pullins Company; New Ed edition May 1, 2002)
- Nicomachean Ethics, Bk. V, ch. 6–7.
- Politics. Bk. III, ch. 16.
- Rhetoric 1373b2–8.
- Shellens, 75–81
- Tony Burns, “Aquinas’s Two Doctrines of Natural Law.” Political Studies 48 (2000): 929–946.
- Aristotle, and Michael Pakaluk. Nicomachean Ethics. Clarendon Aristotle series. Oxford: Clarendon Press, 1998.
- Blackstone, William. Commentaries on the Laws of England. 1765 (9).
- Burns, Tony. “Aquinas’s Two Doctrines of Natural Law.” Political Studies 48 (2000):929–946.
- Jaffa, Harry V. Thomism and Aristotelianism. Chicago: University of Chicago Press, 1952.
- Kainz, Howard P. Natural Law: an Introduction and Re-examination. Open Court, 2004.
- Muhm, Raoul. Germania: La rinascita del diritto naturale e i crimini contro l´umanità. Deutschland: Die Renaissance des Naturrechts und die Verbrechen gegen die Menschlichkeit. Germany: The renaissance of natural law and crimes against humanity.Rome: Vecchiarelli Editore Manziana, 2004.
- “Natural Law.” International Encyclopedia of the Social Sciences. edited by David L. Sills, New York, 1968.
- Robinson, Dave and Judy Groves. Introducing Political Philosophy. Cambridge, UK: Icon Books, 2003.
- Sachs, Joe, trans., Aristotle’s Nicomachean Ethics. Newburyport: MA: Focus Publishing/R. Pullins Company; New Ed edition (May 1, 2002).
- Shellens, Max Salomon. “Aristotle on Natural Law.” Natural Law Forum 4(1) (1959): 72–100.
Originally published by New World Encyclopedia, 11.12.2018, under a Creative Commons Attribution-ShareAlike 3.0 Unported license.