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Natural Law Theories

This entry considers natural law theories only as theories of law. That is not to say that legal theory can be adequately identified and pursued independently of moral and political theory. Nor is it to deny that there are worthwhile natural law theories much more concerned with foundational issues in ethics and political theory than with law or legal theory. A sample of such wider and more foundational theories is the entry Aquinas’ moral, political, and legal philosophy . In the present entry, “natural law theory” is to be taken as shorthand for natural law theories just insofar as they bear on law and are theories of or about it. This focus has the important incidental effect that many historically important differences between natural law theorists can be omitted, differences which pertain more to the foundations of normativity than to the nature and functions (“the concept”) of positive law.

Legal theorists who present or understand their theories as “positivist”, or as instances of “legal positivism”, take their theories to be opposed to, or at least clearly distinct from, natural law theory. Natural law theorists, on the other hand, did not conceive their theories in opposition to, or even as distinct from, legal positivism (contra Soper 1992 at 2395). The term “positive law” was put into wide philosophical circulation first by Aquinas, and natural law theories of his kind share, or at least make no effort to deny, many or virtually all “positivist” theses—except of course the bare thesis that natural law theories are mistaken, or the thesis that a norm is the content of an act of will. Natural law theory accepts that law can be considered and spoken of both as a sheer social fact of power and practice, and as a set of reasons for action that can be and often are sound as reasons and therefore normative for reasonable people addressed by them. This dual character of positive law is presupposed by the well-known slogan “Unjust laws are not laws.” Properly understood, that slogan indicates why—unless based upon some skeptical denial that there are any sound reasons for action (a denial which can be set aside because defending it is self-refuting)—positivist opposition to natural law theories is pointless, that is redundant: what positivists characteristically see as realities to be affirmed are already affirmed by natural law theory, and what they characteristically see as illusions to be dispelled are no part of natural law theory. But because legal theories conceived of by their authors as positivist are, by and large, dominant in the milieux of those likely to be reading this entry, it seems appropriate to refer to those theories along the way, in the hope of overcoming misunderstandings that (while stimulating certain clarifications and improvements of natural law theorizing) have generated some needless debate.

The point made in the preceding paragraph is made in another way by Orrego (Orrego 2007). When the accounts of adjudication and judicial reasoning proposed by contemporary mainstream legal theories are added to those theories’ accounts of (the concept of) law, it becomes clear that, at the level of propositions (as distinct from names, words and formulations), those theories share (though not always without self-contradiction) the principal theses about law which are proposed by classic natural law theorists such as Aquinas: (i) that law establishes reasons for action, (ii) that its rules can and presumptively (defeasibly) do create moral obligations that did not as such exist prior to the positing of the rules, (iii) that that kind of legal-moral obligation is defeated by a posited rule’s serious immorality (injustice), and (iv) that judicial and other paradigmatically legal deliberation, reasoning and judgment includes, concurrently, both natural (moral) law and (purely) positive law. Orrego’s point seems to be confirmed by, e.g., the entry on legal positivism (Green and Adams 2019). Contemporary “positivist” theories are, it seems, natural law theories, distinguished from the main body of natural law theory (a) by their denial that the theory of law (as distinct from the theory or theories of adjudication, judicial duty, citizens’ allegiance, etc.) necessarily or most appropriately tackles the related matters just listed, and accordingly (b) by the incompleteness of their theories of law, that is, the absence from them (and usually, though not always, from their accounts of those related matters) of systematic critical attention to the foundations of the moral and other normative claims that they make or presuppose.

In short: a natural law theory of (the nature of) law seeks both to give an account of the facticity of law and to answer questions that remain central to understanding law. As listed by Green 2019 (having observed that “No legal philosopher can be only a legal positivist”), these further questions (which “legal positivism does not aspire to answer”) are: What kinds of things could possibly count as the merits of law? What role should law play in adjudication? What claim has law on our obedience? What laws should we have? And should we have law at all? All these questions, though organized and articulated a little differently, are under consideration in the present entry.

1.1 Basic reasons for action and the need for governmental authority

1.2 political authority as remedy for anarchy, injustice and impoverishment, 1.3 rule of law as remedy for the dangers in having rulers, 1.4 ius gentium—ius cogens—mala in se —human rights: legal rules and rights posited because morally necessary parts of any legal system, 1.5 “purely positive law”: determinationes and their legal-moral authority for citizens and judges (facts made reasons for action), 2. human persons are not law’s creatures but its proper point, 3.1 adjudicating between exclusive and inclusive legal positivism, 3.2 natural law and (purely) positive law as concurrent dimensions of legal reasoning, 3.3 implications of the rule-of-law need for positivity, 4. “ lex iniusta non est lex ” do seriously unjust laws bind legally, 5. can general theories of law be value-free moral-value-free, 6.1 intention in action and utterance, 6.2 responsibility and punishment, 6.3 each legal system is of and for a particular political community, other internet resources, related entries, 1. enabling positivity: social facts made reasons for action.

The fulcrum and central question of natural law theories of law is: How and why can law, and its positing in legislation, judicial decisions, and customs, give its subjects sound reason for acting in accordance with it? How can a rule’s, a judgment’s, or an institution’s legal (“formal,” “systemic”) validity, or its facticity or efficacy as a social phenomenon (e.g., of official practice), make it authoritative in its subject’s deliberations?

The sense and force of these questions, and the main features of the kind of answer given by natural law theories, can be given a preliminary indication. On the one hand, natural law theory holds that law’s “source-based character”—its dependence upon social facts such as legislation, custom or judicially established precedents—is a fundamental and primary element in “law’s capacity to advance the common good, to secure human rights, or to govern with integrity” (cf. Green and Adams 2019). On the other hand (cf. Green 2003), the question “whether law is of its very nature morally problematic” has from the outset been the subject of consideration by leaders of the tradition. (The first issue that Aquinas takes up about human law in his set-piece discussion of law, Summa Theologiae , I-II, q. 95 a. 1, is whether human law [positive law] is beneficial—might we not do better with exhortations and warnings, or with judges appointed simply to “do justice”, or with wise leaders ruling as they see fit? And see I.3 below.) Classic and leading contemporary texts of natural law theory treat law as morally problematic, understanding it as a normally indispensable instrument of great good but one that readily becomes an instrument of great evil unless its authors steadily and vigilantly make it good by recognizing and fulfilling their moral duties to do so, both in settling the content of its rules and principles and in the procedures and institutions by which they make and administer it. Natural law theories all understand law as a remedy against the great evils of, on the one side anarchy (lawlessness), and on the other side tyranny. And one of tyranny’s characteristic forms is the co-optation of law to deploy it as a mask for fundamentally lawless decisions cloaked in the forms of law and legality.

If one thinks perceptively and carefully about what to pursue (or shun) and do (or forbear from), one can readily understand and assent to practical propositions such as that life and health, knowledge, and harmony with other people are desirable for oneself and anyone else. The intrinsic desirability of such states of affairs as one’s flourishing in life and health, in knowledge and in friendly relations with others, is articulated in foundational, underived principles of practical reasoning (reasoning towards choice and action). Such first principles of practical reasoning direct one to actions and dispositions and arrangements that promote such intelligible goods, and that directiveness or normativity is expressed by “I should…” or “I ought…” in senses which although truly normative are only incipiently moral.

A natural law moral theory will give an account of the way in which first principles of practical reason take on a moral force by being considered, not one by one but in their united (“integral”) directiveness. That integral directiveness is given specific (albeit highly general) articulation in principles such as the injunction to love one’s neighbor as oneself; or the Golden Rule of doing for others what you would want them to do for you and not doing to others what you would not have them do to you; or the “categorical imperatives” to respect, and treat as intrinsically valuable, humanity (the basic aspects of human flourishing) in oneself and in others, so that each of one’s communities is treated as a kingdom of ends—of persons each ends in themselves. Such high-level but far from contentless moral principles can be given further specificity in two ways (1) by identifying what, given some broadly stable features of human reality, they entail (see 1.2–4), and (2) by a rational but more or less non-deductive selection among alternative specifications, a selection named by Aquinas determinatio (plural, determinationes ) (see 1.5). Political communities are a kind of institution whose rational status as a normally desirable and obligatory objective of and context for collaborative action (and forbearance) can easily be seen to be entailed by the foundational practical and moral principles. In such communities, the normal means for making the needed determinationes is the institution of governmental authority acting in the first instance through legislation and other forms of law-making, i.e., acting as a social-fact source of positive (posited) law.

The political-theoretical part of natural law theory explains and elaborates the grounds and proper forms of governmental authority. It explains the similarities and differences between the practical authority of rulers (including democratic electors acting as selectors of representatives or as plebiscitary decision-makers) and the theoretical authority of experts and persons of sound judgment. It shows the grounds for instituting and accepting practical authority as an almost invariably necessary means for preventing forms of harm and neglect which, because contrary to the high-level moral principles (at least as they bear on relationships between persons), involve injustice. Political theory subsumes, as one of its branches, legal theory. As legal theory, political theory explains the normal desirability that governmental authority in political communities be exercised within the framework of (in the classic slogan) a “rule of law and not of men” (1.3).

1.1.1 Why “natural” law? Naturalistic fallacy?

What does the mainstream of natural law theory intend by using the word “natural” in that name for the theory? The shortest accurate answer is “of reason,” as in “the law of reason” or “the requirements of reason.” Aquinas is particularly clear and explicit that in this context, “natural” is predicated of something (say, a law, or a virtue) only when and because that of which it is predicated is in line with reason, practical reason, or practical reason’s requirements: see Finnis 1980, 35–6. Moreover, he employs, through all his works, a methodological axiom: X ’s nature is understood by understanding X ’s capacities, which are understood by understanding their act[uation]s, which are understood by understanding their objects. But the objects of chosen acts are the intelligible intrinsic goods (aspects of human flourishing) which we are directed to by practical reason’s first principles. So the equation, in this context, of “natural” and “rational” and its cognates is no mere confusion, but grounded in a sophisticated distinction between ontology and epistemology: in the order of being, what is good and reasonable for us is a resultant of what is foundational, our given nature; but in the order of coming to know, our knowledge of our nature is in significant part a resultant of our understanding of what kinds of possible objects of choice are good.

Though the core of classic and mainstream natural law theory is thus untainted by any “naturalistic fallacy” (Finnis 2018, 2.4.2), non-practical knowledge of facts counts, in that theory, in various ways. Knowledge of the factual possibility of (say) acquiring knowledge, or of losing or saving life, is a datum (not really a premise) for the understanding that such a possibility is also an opportunity—that actualizing the possibility would be good for oneself and others. Other kinds of relevant facts include the facts about certain human radical capacities and their absence in other animals—these facts are the data for the insight into the sense and bounds of the class (persons, human beings) of “others” in “good for oneself and others.” Or again, facts about the limited supply of resources and the limited strength of human will (the need for incentives, etc.) make (1.5) appropriation of resources to particular owners a normal requirement of justice to non-owners and owners alike.

The texts that are earliest (e.g., the Platonic or pseudo-Platonic Minos : Lewis 2006) and most foundational (e.g., Plato’s Gorgias, Republic and Laws , and Aristotle’s Politics ) in the tradition of natural law theory remind their readers of the evident evils of anarchy: a condition of things in which no person or body of persons efficaciously claims or is accepted widely as having authority to restrict the use of violence, theft and fraud, and in which any conventional norms of conduct are made hollow by irresolvable disputes about their content and/or their application. In such a state of affairs, the more strong, cunning and ruthless prey on the less, education of children (which calls for resources outside the family) is difficult to accomplish, and economic activity remains stunted by the insecurity of holdings and the unreliability of undertakings. There is evident need for persons who will articulate and enforce standards of conduct which will tend to promote the common good of bodily security, stable access to resources, cooperation in economic and educational activities, and rectification (by punishment, compensation and restitution) of at least the grosser inter-personal injuries of commission and neglect. To articulate that need is to state the reasons for instituting and supporting political authority, notably state government and law, on condition that these institutions carry on their legislative, executive and judicial activities substantially for the common good of the inhabitants of the relevant territory, rather than in the interests of a segment of the population unfairly indifferent or hostile to the interests and wellbeing of other segments.

Aristotle ( Politics III.15.1286a–IV 4 1292a) vigorously debates the question whether political authority is better exercised through a “rule [primacy, supremacy] of law” or “a rule of men,” say of one best person, or a democratic assembly, or indeed ( Rhetoric I 1 1354a32–b16) a court. He takes his arguments to suggest the answer that in almost all societies, on almost all occasions and issues, it is preferable that government be by or in accordance with law, since (i) laws are products of reason(s) not passion(s), (ii) the sovereignty of a ruler or assembly tends to tyranny (i.e., rule in interests of a section, not common good), (iii) equality demands that each mature person have some share in governing, and (iv) rotation of offices and office-holders is desirable and can hardly be managed without legal regulation. So for Aristotle, the central case of practical authority is government of a polis by law and legally regulated rulers.

Thomas Aquinas’ account of human positive law treats the central case of government as the self-government of a free people by the rulers and institutions which that people has appointed for that purpose, and the central case of law is the co-ordination of willing subjects by law which, by its public character (promulgation), clarity, generality, stability and practicability, treats those subjects as partners in public reason ( Summa Theologiae I-II q. 90 a. 4c; q. 95 a. 3c; q. 96 a. 1; q. 97 a. 2). For he defines law as universal (in the logician’s sense of “universal”) practical propositions conceived in the reason of the ruler(s) and communicated to the reason of the ruled so that the latter will treat those propositions, at least presumptively, as reasons for action—reasons as decisive for each of them as if each had conceived and adopted them by personal judgment and choice.

Lon Fuller 1969, acknowledging Aquinas’ lead in this discussion of formal and procedural aspects of legal system, pulls together Aquinas’ scattered and fragmentary remarks about them into an orderly list of eight elements of the rule of law , that is of la primauté du droit , the legal system of a Rechtsstaat . He shows that these hang together as a set of desiderata (or requirements) because they are implications or specifications of the aspiration and duty to treat people as presumptively entitled—as a matter of fairness and justice—to be ruled as free persons, fundamentally the equals of their rulers, not puppets or pawns to be managed and kept in order by manipulation, uncertainty, fear, etc. The normal result of such fairness in the procedures of making and maintaining the law will be to strengthen the law’s efficacy, too. Unfortunately, the surface of Fuller’s text gives more prominence to effectiveness than to fairness, and many critics (e.g., Hart, Dworkin), overlooking the moral connotations of Fuller’s allusions to reciprocity between rulers and ruled, thought his book’s title, The Morality of Law , a misnomer. This thesis has been elaborated more carefully and on a different basis by Raz 1979 and Kramer 2004a and 2004b: although the rule of law (and compliance with it) can be morally important and even a moral virtue (because normally necessary for fully just government in a just society, and especially for alleviating dangers that arise from the existence of political authority, and of law itself), it is nonetheless in itself morally neutral since (in states which employ the forms of law) it will normally be needed even by deeply unjust rulers for advancing their immoral purposes. It is like a sharp knife, whose sharpness makes it apt for life-saving surgery but equally for stealthy callous murders (Raz 1979, 224–6).

Finnis 1980 (273–4) and Simmonds 2004, 2005, 2006, 2007 have challenged the quasi-empirical claim that even vicious tyrants need or find it apt, for the efficacy of their domination, to comply with the requirements of the rule of law. The eighth of Fuller’s elements of the rule of law, viz. adherence by the rulers to their own rules in their conduct of government, is especially obstructive, rather than supportive, of a tyranny’s purposes. But the focus of Fuller’s concern, and the most fruitful locus of debate, is not so much on historical or sociological phenomena or causalities as on the “internal,” practical reasons at stake. If the rulers somewhere do not respect the rights and interests of some of their subjects in relation to issues of substance (life, bodily security, freedom, property, and so forth), why should the rulers—what reason have they to—respect their subjects’ rights or interests in the matters of procedure involved in the rule of law (giving them fair notice of what is expected of them, and adhering as rulers to the promulgated law when assessing these subjects’ conduct and in other governmental dealings with those subjects)? A more or less inconsistent willingness of rulers to tie their own hands by scrupulous adherence to procedural justice while yet being substantively unjust, is of course psychologically possible. But Fuller’s primary concern, like that of the wider tradition of natural law theory, is with rationality and the specific implication of fully coherent reasonableness: morally reasonable judgment and choice.

Fuller offered a merely procedural natural law theory, though he did not deny that a substantive natural law theory is possible and appropriate. And indeed there is no sufficient reason to follow him in restricting the range of practical-theoretical reflection on what is needed for a political society worthy of the self-restraints and acceptance of responsibilities that the law requires of those to whom it applies. For it is clear that the procedures and institutions of law are in the service of substantive purposes: the restriction of violence, theft and fraud, the recovery of things misappropriated from their lawful owners or possessors, and of losses wrongfully imposed, protection of intangible goods such as reputation against unwarranted defamation, and of the immature, the mentally disabled and other vulnerable people against sexual or other exploitation, and so forth.

That portion of our positive law which consists of legal principles or rules giving effect to purposes such as those just listed was often named, by natural law theories, ius [or jus ] gentium . Minted by jurists of classical Roman law such as Gaius (c. 165 AD), this name—literally “the law of peoples”—alludes to the set of rules and principles found in similar if not identical forms in virtually all legal systems. The reason for their ubiquity is, generally speaking, that any reasonable consideration of what it takes for individuals, families and other associations to live together in political society, tolerably well, will identify these principles and rules as necessary. In modern law they are picked out, in principle, by names such as “the general principles of law recognized by civilized nations” (Statute of the International Court of Justice, art. 38), ius cogens erga omnes (literally “law that is compelling [obligatory without agreement or enactment or other forms of adoption] in relation to [for/on, ‘against’] everyone”), “higher law”, or “fundamental human rights.” In Aquinas’s theory of law, they are referred to as conclusions (entailments) of the very highest-level, most general moral principles. In the common law tradition, the legal wrongs picked out by such principles have been called mala in se , as distinct from mala prohibita —things wrong in themselves as distinct from things wrong only because prohibited by (positive) law—and this distinction remains, for good reason, in use in judicial reasoning.

Some legal theories speak of these principles and rules as belonging to law by a kind of “conceptual” necessity. Hart (1961) can be so read. But even Hart’s account, on closer examination, identifies the relevant necessity not as conceptual or linguistic but as an instance of the rational necessity of means needed to secure purposes which are non-optional. It was for this reason that Hart spoke of them as constituting “the minimum content of natural law.” He would have expressed his own meaning more perspicuously had he spoken instead of “the minimum content of positive law, the minimum set of principles which, because rationally necessitated —given certain fundamental ‘truisms’ about human nature and the human predicament—for the securing of purposes shared by all survivable human societies, can be called natural law.” The fact is that these elements of our law are both positive (made and part of official practice) and natural (rationally required for at least minimal human flourishing).

These issues are discussed further in Section 3 below.

Natural law theory of law has its most distinctive characteristic in its account of purely positive law which, though “entirely” dependent for its legal status on the fact that it has been authoritatively posited by some persons(s) or institution, nonetheless shares in law’s characteristic of entailing—albeit presumptively and defeasibly—a moral obligation of compliance. About these rules of a positive legal system, Aquinas says that, though they certainly should be, and be presumed to have been, “ derived from natural law”, they have their legal force only from their part in this posited system ( ex sola lege humana vigorem habent : ST I-II, q. 95 a. 3).

His explanation, slightly updated: this very large part of our law could reasonably have been different, in the way that every detail of a maternity hospital could have been somewhat different and large portions of the design could have been very different, even though some features (e.g., that the doors and ceilings are more than two feet high) are entailed by the commission to build a town maternity hospital, and every feature has some rational connection with the commission. The kind of rational connection that holds even where the architect has wide freedom to choose amongst indefinitely many alternatives is called by Aquinas a determinatio of principle(s)—a kind of concretization of the general, a particularization yoking the rational necessity of the principle with a freedom (of the law-maker) to choose between alternative concretizations, a freedom which includes even elements of (in a benign sense) arbitrariness.

Once the determinatio is validly made, fulfilling the criteria of validity provided by or under the relevant legal system’s constitutional law, it changes the pre-existing state of the law by introducing a new or amended legal rule and proposition(s) of law. The new or amended legal rule gives judges, other officials, and citizens a new or amended reason for action (or forbearance). The fact that the new or amended rule depends upon the social-fact source constituted or employed by the act of determinatio does not entail that a normative reason (an “ought”) is being illogically derived from a bare fact (an “is”). Rather, the new or amended rule is normative, directive and (where that is its legal meaning ) obligatory because that social fact can be the second premise in a practical syllogism whose first premise is normative: “there ought to be a maternity hospital in this town,” “people ought to be protected against homicidal assault,” “people ought to be required to contribute to the public expenses of appropriate governmental functions”, “victims of assault, theft, broken contracts, negligence, etc., ought to be compensated,” “road traffic should be regulated to reduce damaging collisions,” and so forth. The moral normativity of the principle is replicated in the more specified rule created by the determinatio , even though the latter is not an entailment of the former.

That is to say: the concretized rule is (morally as well as legally) normative because such normativity is (presumptively and defeasibly) entailed by the (moral) principle that the common good (whose fundamental content is given by the foundational principles of practical reason: 1.1) requires that authoritative institutions take action to specify, apply and enforce some rules on the relevant matters. Social facts make a positive legal rule a reason for action because the desirability of authority as a means of securing common good, and the desirability of the “rule of law and not of men,” are standing and potent reasons for acknowledging such facts as an instance of valid legislation giving presumptively sufficient reason for compliance. Purely positive law that is legally valid is (presumptively and defeasibly) valid and binding morally—has the moral form or meaning of legal obligatoriness —when and because it takes its place in a scheme of practical reasoning whose proximate starting point is the moral need for justice and peace, and whose more foundational starting-point is the range of basic ways in which human wellbeing can be promoted and protected, the way picked out in practical reason’s first principles.

Thus, in relation to the settled positive law, natural law theory—as is acknowledged by a number of legal positivists, (e.g., Raz 1980, 213; Gardner 2001, 227)—shares the principal thesis of contemporary legal positivists, that laws depend for their existence and validity on social facts.

1.5.1 “Presumptive” and “defeasible” obligatoriness

The legal-moral obligation or obligatoriness of a legal rule is counterpart to the legal-moral authority or authoritativeness of its author (enacter) or other source. The idea of authority has been clarified by contemporary legal theorists such as Raz and Hart, by reflection upon the kind of reasons for action purportedly given to potentially acting subjects by an exercise of practical authority. The relevant kind of practical reason has been variously called exclusionary, peremptory or pre-emptive, and content-independent. The core idea is that subjects are instructed to treat the proffered reason (say, a statutory provision, or a judicial order), in their deliberations towards choice and action, as a reason which does not simply add to the reasons they already have for acting one way rather another, but rather excludes and takes the place of some of those reasons. And this exclusionary, peremptory or pre-emptive force is owed not to the inherent attractiveness to reason of the (content of the) proffered reason, but to the status of its author or other source as one entitled—for example, by its role in a constitutional scheme of governance for the solution of a political community’s coordination problems—to be obeyed, complied with, treated as authoritative. See e.g., Raz 1986, 35–69. This content-independence of authoritative reasons entails their presumptive obligatoriness. The defeasibility of that presumption is entailed by the dependence of such reasons’ peremptory, pre-emptive or exclusionary force upon a background of presupposed basic human needs and goods, and of basic moral principles and norms, a background which entails that if a purportedly authoritative proffered (posited) reason conflicts sufficiently clearly with those standing needs, goods, principles or norms its exclusionary force is exhausted or overcome and the purported obligatoriness defeated.

Less abstractly put, both the effectiveness of laws as solutions to coordination problems and promoters of common good, and the fairness of demanding adherence to them, are dependent upon their being treated both by the subjects and the administrators of the legal system as legally and morally entitled, precisely as validly made law, to prevail against all other reasons save competing moral obligations of greater strength. It is this entitlement that is negated by the serious injustice of a law or legal system: see 3 and 4 below.

Talk of human flourishing’s or wellbeing’s aspects, and of principles of practical reason, should not be allowed to distract attention from an important truth, implicit both in classical Greek and Roman philosophical and juristic treatments of justice and in modern juristic attributions of human rights. Indeed, the Universal Declaration of Human Rights (1948) links the two traditions of discourse by placing at the head of its articulation of human rights the core (“all human beings are born free and equal in dignity and rights”) of the Roman juristic saying ( Institutes 1.2.2) that “by nature, from the outset, all human beings were born free and equal,” a saying about iustitia , justice as a ground and standard for ius , law. The same Roman law texts, promulgated as permanent law by Justinian 533–535 AD, state more than once that law’s point (its “final” causa , explanatory reason) is the human persons for whose sake it is made, that is, all human persons until the time when the ius gentium , the common law of peoples, was distorted by wars and slavery. Law, fit to take a directive place in practical reasoning towards morally sound judgment, is for the sake of human persons: all the members of the community regulated by that law and all other persons within that law’s ambit.

That thesis falls within those parts of legal theory that are acknowledged but not much explored by contemporary legal positivists. It was ignored and in effect denied by earlier forms of legal positivism more ambitious to cover the whole of legal philosophy, e.g., Kelsen’s. Kelsen denied that persons were known either to law or to a proper legal theory or science of law, except insofar as they were made the subject of a posited legal rule. But against this restriction, which has misled some courts which have treated Kelsenian legal science as a guide to judicial reasoning, it can be said (Finnis 2000) that the fundamental equality and dignity of human beings should defended as part of a rationally sound understanding (concept) of law. This defense requires an account of the difference between capacities which are activated here and now, or are more or less ready to be so actuated, and radical capacities such as exist in the epigenetic primordia of even very young human beings, and in the genetic and somatic constitution of even the severely disabled. Though such an account makes possible a defense of the fundamental equality of human beings, and thus a humanist legal theory, the point of the account is not to privilege a biological species as such, but to affirm the juridical significance of the status of persons—substances of a rational nature—as inherently the bearers ( subjects ) of rights of a kind different and more respect-worthy and end -like than the rights which are often, as a matter of technical means , attributed by law to animals, idols, ships or other objects of legal proceedings.

3. Legal principles to remedy defective positive law

The so-called positivist thesis that all law depends for its existence, validity and obligatoriness on its social-fact source(s) is often accompanied, as in Raz’s “exclusive legal positivism” (Raz 1980, 212–24; Raz 1985), by the thesis that judges, as the “primary law-applying institutions,” have a duty (moral, if not also legal) to decide certain sorts of case (e.g., cases where the existing legal rule would by work injustice) by applying moral principles or rules which warrant amending or even abandoning part of the existing law. “Inclusive” legal positivists temper this by holding that the judicial duty and authorization to depart from existing law by applying moral rules or principles is restricted to those classes of case where an existing social-fact sourced legal rule directs the court do so; the effect of such a directive, it is said, is to include within the legal system the moral rules or principles (if any) thus pointed to.

Natural law theory concurs with Raz and Gardner in rejecting the inclusivist restriction as ungrounded, but dissents from them in holding (as Dworkin does too: Dworkin 1978, 47) that any moral rule or principle which a court is bound to apply (or reasonably can apply), precisely as a court, can reasonably be counted or acknowledged as a law, i.e., as a rule or principle which should be considered already part of our law. Against positivists generally, it holds that (i) little or nothing turns on whether or not moral principles binding on courts precisely as courts should be called part of our law; but (ii) if something does turn on the name—if, for example, it be recalled that courts cannot “take judicial notice” of any rule or principle not “part of our law” (and so, as in respect of rules of foreign law, have to hear evidence of the rule’s existence and content)—it is sounder to say that judicially applicable moral rules and principles (unlike applicable foreign law) are ipso iure (i.e., precisely as morally and judicially applicable) rules of law . Such rules belong to the ius gentium portion of our law.

Does this amount to acknowledging that natural law theory is significantly less concerned than contemporary legal positivist theories to establish the precise boundaries and content of the social-fact sourced (posited, purely positive) law of our community? Not really. For (i) contemporary legal positivist theories have abandoned the thesis of “classical” legal positivists such as Bentham that judges and citizens alike should (as a matter of political-moral obligation) comply with the positive law of their community: their treatises or essays on legal theory explicitly or implicitly commend to judges as much as citizens the Hartian “This is law; but it is too iniquitous to be applied or obeyed” (Hart 1961, 203; 1994, 208) rather than the Benthamite “Under a government of laws … obey punctually and … censure freely” (Bentham 1776); so the concern of contemporary legal positivists to distinguish posited law from other standards for sound and legitimate adjudication turns out, in the last analysis (and despite appearances), to be merely provisional. And on the other hand (ii) natural law theories hold as strongly as any positivist theory that sound and legitimate adjudication gives priority to a conscientious and craftsmanlike attention to social-fact sources and to rules and principles pedigreed by such sources, sets them aside only if and to the extent that they are “too iniquitous to be applied”, and tailors the resultant new rule so as to cohere as far as possible with all the other (not too iniquitous) doctrines, rules and principles of the particular legal system in which the judge has jurisdiction.

3.1.1 A test case: the Nuremberg question

The persons known as major German war criminals were tried in 1945 for offenses specified in an agreement (“the London Agreement and Charter of 8 August 1945”) made between the states governing Germany since its surrender to them. The judges held that the defendants had at all relevant times been bound by (and in many instances had acted in violation of) the principles or rules specified in the London Charter, such obligations being derived not, of course, from the agreement (which was made subsequent to the acts in question), but rather, as to some of the crimes alleged, from international law and, as to the alleged “crimes against humanity,” from the “elementary dictates of humanity.” To hold the defendants responsible for violating these rules and dictates, and reject any argument that their acts’ compliance with German law could make them lawful acts, was not (so the tribunal ruled) to violate the principle of law and justice that no one should be punished except for violation of law .

The result of these rulings might be accounted for (i) by exclusive positivism: the tribunal was morally authorized to apply moral rules, notwithstanding that the rules so applied were not rules of law either at the time of the crimes or the time of the prosecution. But the terms of the rulings (as just summarized) can be accounted for (ii) by inclusive positivism: the Charter was positive law for the tribunal and directed it to apply moral rules which by virtue of that legal direction were also legal rules. Still, (iii) natural law theory’s account seems the most explanatory: the moral rules applied were also rules of the “higher law” applicable in all times and places (and thus in Germany and its territories, before as after the Charter) as a source of argumentation and judgment “according to law” when the social-fact sources which are the normally dominant and quasi-exclusive source of law are, in justice, inadequate and insufficient guides to fulfilling obligations such as the judicial obligation to do justice according to law, or everyone’s obligation to behave with elementary humanity even when under orders not to—even if those orders have intra-systemic legal validity according to the formal or social-fact criteria of some existing legal system. And if one has doubts about victors’ justice, those very doubts can likewise appeal to principles of the same higher law, ius gentium , or law of reason and humanity.

Natural law theory of law thus finds itself, in this respect, approximated to by Ronald Dworkin’s account of law and adjudication, not only in frontier situations like Nuremberg but also in the day-to-day working of a sophisticated legal system. Normal adjudication and judicial reasoning has two dimensions or criteria for distinguishing correctness from incorrectness in judgments. One dimension comprises social-fact sources (statutes, precedents, practice, etc.), called by Dworkin “legal materials.” The other dimension comprises moral standards, presumptively those prevalent in the judge’s community but in the last analysis just those standards that the judge can accept as in truth morally sound. An interpretation of our law which is morally sounder will be legally correct even if it fits the legal materials less closely than alternative interpretations, provided that it fits those social-fact sources “enough.” The moral standards thus applied, which Dworkin (in line with natural law theory) treats as capable of being morally objective and true, thus function as a direct source of law (or justification for judicial decision) and, in a certain sense, as already law, except when their fit with the whole set of social-fact sources in the relevant community is so weak that it would be more accurate (according to Dworkin) to say that judges who apply them are applying morality not law (and thus, if they said they were applying law, would be mistaken or lying—a lie which Dworkin considers sometimes commendable). Dworkin 1978, 326–7, 340.

A theory of law which, unlike Dworkin’s, places itself plainly in the tradition of natural law theorizing will be likely to depart from these positions in two ways. (i) It will not accept Dworkin’s thesis that even in very hard cases there is one uniquely correct answer in law; it will deny his assumption that there is a uniquely correct and rationally identifiable measure of how much fit with existing legal materials (social-fact sources) is “enough” (necessary and sufficient) to license using moral standards to identify the legally correct interpretation of the law. In the absence of such a single measure, legal reasoning must often—and in very hard cases, usually—be content to show that two or three alternative interpretations are distinguished from an indefinitely large number of other interpretations by being correct, that is, not wrong (albeit not uniquely correct). (ii) When judges, in order to avoid grave injustice, depart from the settled understanding of the law (and perhaps from the clear terms of a decree) and apply an alternative, morally mandated interpretation, regarding themselves as licensed to do so by the higher law of reason, nature and humanity, they need not be lying if they say that in doing so they are both rectifying and applying the law (of their state). See 4 below.

In line with Dworkin’s two-dimensions account (thus qualified), natural law theory will assent to the thesis that Green makes characteristic of legal positivism:

[1] the fact that a policy would be just, wise, efficient, or prudent is never sufficient reason for thinking that it is actually the law, and [2] the fact that [a law] is unjust, unwise, inefficient or imprudent is never sufficient reason for doubting [that it is law].

For as to [1]: what the rule of law and not of men calls for is the institution of legal system , a corpus iuris , and so what a principle of morality (natural law) or ius gentium implies would be an appropriate rule of law is, nevertheless, not yet a part of our law—still less is a mere “policy” made law by being “prudent” or “efficient”—unless its content, conceptualization and form are so shaped, whether in judicial or other juristic thinking or in judgment or legislation, as to cohere with the other parts (especially neighboring parts) of our law.

As to [2]: A natural law theory, mindful of the normal desirability of a rule of law and not of judges (see 1.3), may well be more cautious than Dworkin himself is in departing from the settled (social-fact source-based) law. On those occasions where such a departure is morally warranted, the theory will suggest that the judge is authorized to proceed according to the higher and perennial law of humanity, the ius gentium or set of universal principles of law and justice common to all civilized peoples, which deprives settled law—more precisely, what has been accepted in the jurisdiction as being settled law—of its directiveness for subjects and judges alike. Is this moral authorization also ‘legal’ and “according to law”? Is the settled law which the judge is morally authorized to set aside thereby being treated, even prior to the judge’s handing down of judgment, as not law? The following section argues that that question should be answered both Yes and No.

In such a case, does the law as settled by social-fact sources, in losing its directiveness for judges and citizens, lose also its legal validity? The answer depends upon the discursive context in which the question arises. If a course of reflection or discourse makes it appropriate to acknowledge the rule’s “settled” or “posited” character as cognizable by reference to social-fact sources, one can say that it is legally valid though too unjust to be obeyed or applied. Or if the discursive context makes it appropriate instead to point up its lack of directiveness for judges and subjects alike, one can say that the rule, despite its links to social-fact sources, is not only not morally directive but is also legally invalid. Each way of speaking tells an important part of the truth, or rather, tells the truth with an emphasis which differs from the other’s.

The meaning of “an unjust law is not a law” is essentially identical to Hart’s “This is law but too iniquitous to be applied or obeyed” (or availed of as a defense). The excitement and hostility aroused amongst modern legal theorists (notably Hart) by the former way of speaking is unwarranted. No one has difficulty in understanding locutions such as “an invalid argument is no argument,” “a disloyal friend is not a friend,” “a quack medicine is not medicine,” and so forth. “ Lex iniusta non est lex ” has the same logic; it acknowledges, in its opening words, that what is in question is in certain important respects—perhaps normally and presumptively decisive respects— a law , but then in its withdrawal or denial of that predicate it affirms that, since justice is the very point of having and respecting law at all, this particular law’s deficiency in justice deprives it of the decisive significance which all law purports to have. It is thus law only in a sense that should be judged—especially when law is regarded, as by Hart himself, as a kind of reason or purported reason for action—to be a distorted and secondary, non-central sense.

Note: Classical political theory, as expounded by Plato, Aristotle and Aquinas, makes regular use of this distinction between central and perverted or otherwise marginal instances of an analogical concept or term, and so Aquinas never says simply “unjust law is not law” but rather “unjust law is not straightforwardly or unqualifiedly [ simpliciter ] law” or “is a perversion of law”, and similar statements. Still, he does elsewhere say that “an unjust judgment [of a court] is not a judgment” and it seems clear that he might similarly have used the simplified or slogan-form locution, about law, as short-hand.

All this seems to have been overlooked by Hart in his polemic (Hart 1961, 204–7; 1994, 208–12) against “ lex iniusta non est lex .” Hart’s argument that use of the slogan must tend to discourage or confuse the moral critique of law seems historically and logically indefensible. The slogan is unintelligible save as an expression of and incitement to engaging in such critiques; it can scarcely be rejected without first misquoting it, as Hart and those who employ his argument almost invariably do, averting their gaze from the slogan’s first predication and implied assertion: that the unjust rule in question is a rule of law .

Some theories have adopted certain main tenets of natural law theory, and professed to be natural law theories, but have asserted that even the most unjust laws create an obligation to obey which is both legal and moral. Kant’s (see Alexy 2002, 117–121) is such a theory: a legal system can consist entirely of positive law but must be “preceded by a natural law that establishe[s] the legislator’s authority…to bind others simply by his arbitrary action.” But this purported natural-law basic norm looks not to the justice of the content of the posited legal rules, but exclusively to the need for legal certainty and civic peace, which Kant takes to exclude any right to resist unjust laws and any denial that they are fully legal. Alexy has pointed out the confusions and inconsistencies in Kant’s attempts to evade the classic position that laws whose injustice is sufficiently grave can and should be denied to have the legal character predicable of laws that citizens and courts, precisely as courts, are morally and juridically entitled to treat as—or as if they are—not law. In this as in many other respects, seventeenth and eighteenth century philosophical developments (like their twentieth and twenty-first century counterparts) were not so much progress as regress. But precisely how the classic position itself should be formulated, explained and applied today is debated between Alexy, Finnis and others (Alexy 2013; Finnis 2014; Crowe 2019).

Descriptions of the valuations made by particular persons or societies can of course be value-free. Doubtless the historian, detective or other observer thinks there is some value in making the investigation and resultant description, but that valuation in no way need enter into the description. Still less need the description either approve or disapprove of the valuations which it reports. But the situation is different if one’s aspiration is to offer a general account of human practices or institutions, such as law , friendship, constitutions, and so forth. Here one confronts the necessity of selecting and prioritizing not merely the investigation itself but rather some one set of concepts (and corresponding terms) from among (or over and above) the range of terms and concepts already employed in the self-understanding of the individuals and groups under (or available for) study.

Where the subject-matter of the projected descriptive general account is some practice or institution devised by (more or less adequate exercises of) reason, and addressed to the rational deliberations of individuals and groups, there will normally be no good reason not to prioritise those forms of the practice or institution which are more rational, more reasonable, more responsive to reasons, than other forms of the “same” or analogous practices and institutions. The standard for assessing reasonableness for this theoretical purpose is, in the last analysis, the set of criteria of reasonableness that the descriptive theorist would use in dealing with similar practical issues in his or her own life.

This necessity of value-laden selection of concepts and terms for use in a general theory of social realities such as law is evidenced in the work of Max Weber, prophet of “value-free” social science. His account, for example, of forms of domination ( Herrschaft ) identifies three pure, central, characteristic types ( Idealtypen ): charismatic, traditional, and rational (bureaucratic, legal). But the accounts of the first two types are almost entirely in terms of how they differ from the rational type, whose rationality is self-evident to Weber and his readers on the basis of their own knowledge of human goods (basic aspects of human wellbeing) and related practical truths. See Finnis 1985, 170–72. Natural law theory, as one sees it practiced already in Aristotle’s Ethics and Politics , makes these valuations by the theorist overt and explicit (not hidden and embarrassed), and subjects them to rational scrutiny and debate.

Raz, Dickson, and others accept that some such valuation is necessary, but deny that it is moral: Dickson 2001. But once one begins to deal in reasons, can anything other than good reasons count? If moral reason is nothing more than practical reason at full stretch, fully critical and adequate as reason, moral reasons will have a decisive place in concept-formation in social science including descriptive general theory of law. And this will not have the effect feared by Hart, viz. of leaving the study of wicked laws or institutions to some other discipline: Hart 1961, 205; 1994, 209. On the contrary, they are a subject of lively attention in such a theory, precisely because of their opposition to legal systems of a (substantively and procedurally) morally good kind. Aristotle’s Politics , though not methodologically flawless overall, is a primary witness to this sort of clear-eyed acknowledgment and depiction of unreasonable social forms, practices and institutions within a descriptive theory oriented by the moral judgments of the theorist.

Still, descriptive social theory is only a subordinate aspect of natural law theories of law. Their primary focus is typically on identifying the conditions under which law is justified, both in the sense in which law can and should be preferable to anarchy or tyranny or even benevolent “rule of men,” and in the sense in which this or that legal principle, institution or rule can be judged to be preferable to alternative reasons or purported reasons for action. As Green 2003 says:

Evaluative argument is, of course, central to the philosophy of law more generally. No legal philosopher can be only a legal positivist. A complete theory of law requires also an account of what kinds of things could possibly count as merits of law (must law be efficient or elegant as well as just?); of what role law should play in adjudication (should valid law always be applied?); of what claim law has on our obedience (is there a duty to obey?); and also of the pivotal questions of what laws we should have and whether we should have law at all. Legal positivism does not aspire to answer these questions, though its claim that the existence and content of law depends only on social facts does give them shape.

Might it not be better to say: no legal philosopher need, or should, be a legal positivist? For law’s dependence upon social facts is fully acknowledged, and also accounted for, in natural law theories of law. And this is not a “concession” by natural law theorists, for their main positions were clearly articulated by Aquinas, many centuries before legal positivism emerged with its challenge to (what it took to be) natural law theory. Positivist critiques of natural law theory, when they do not rest upon scepticism about the possibility of moral judgment, a scepticism implicitly disavowed in the above passage, rest on misunderstanding of passages from the works of natural law theorists. On such misunderstandings, see Finnis 1980, 23–55; Soper 1992.

Again: How could such fundamental questions as “Should we have law at all?” be “given shape” by the positivist thesis that law’s existence and content depends only on social facts? Does not Green’s claim invert the reasonable order of inquiry and reflection? Basic human needs and circumstances powerfully suggest to people in virtually all times and places that they should make and uphold some norms of the kind we call law, norms which will depend directly and for the most part on social facts such as custom, authoritative rule-making, and adjudication. Legal philosophy retraces and clarifies, critically, that elemental practical reasoning, somewhat as Hart did in Hart 1961, where he constructs a descriptive-explanatory account of law (i.e., refines his and our concept or understanding of law) by explaining how rules differ from habits, how powers have different functions and social value from obligations and so are not aptly reducible to obligations (and so also why power-conferring rules are distinct from duty-imposing rules), and how “primary” rules for outlawing gross violence, theft and fraud need , by reason of their lack of certainty in content and application and their immobility, to be supplemented by “secondary” rules of recognition, adjudication and change, the remedial supplementation that shifts a society into the domain and rule of law and legal system. May not those elements in Hart’s book be taken as an instance of natural law legal theory done in a primarily descriptive (rather than primarily justificatory) mode, and with incomplete scrutiny of the resources of practical reason, resources being drawn upon by the whole explanatory general description of law? Does not Hart’s description, despite its incompleteness, work as well as it does precisely because it disinters some elementary justifications conceived and put to use by the people whose activities provide the material for the descriptions? Does he not share the deep methodology of Aristotle and the natural law tradition (Finnis 2003) in making his identification of what law is (of “the concept of law”) depend upon his account of why law is a reasonable response to common human needs?

Again, the question perhaps most central to a general theory of law, namely whether law can have a nature, and if so whether it is to be understood on the model of artefacts, or alternatively by study of concepts (“conceptual analysis”), seems to tackled with most explicitness and attention to different and related kinds of subject-matter by theorists working in the philosophical tradition that is or concerns the topic of this entry: Murphy 2015; Finnis 2020.

None of this is to say that a sound legal theory of the kind explained in this entry need be called “natural law theory.” Like all philosophy, it should be done by considering propositions, not labels.

6. Other elements of natural law theory

Intended to be part of a comprehensive theory of practical reasons that are fit to direct us to the common good of each of our communities and its members, any natural law theory of law brings to bear on law all the theses proposed and defended in natural law theory’s moral and political parts and in a sound understanding of the human makeup and of the lasting characteristics of our circumstances. So, besides the questions listed by Green as quoted in section 5 above, issues such as the following three (see others in Finnis 2002) are treated by natural law theory as integral to legal science, theory or philosophy.

Rules of law are propositions of practical reason, apt for being taken as directive in the deliberations of law’s individual subjects towards judgment, choice (decision), and action (including chosen forbearance). So a sound theory of law will have an integrated and critical understanding of the structure of chosen action, particularly of the relationships between the intending of ends, the adoption of means, the dual character of almost all ends as also means, and of almost all means as also ends, and the necessity and normal possibility of freely choosing between options which embody or promise benefits and disadvantages incommensurable (incompletely commensurable) (Finnis 1997) with the benefits and disadvantages of the alternative options. Such an understanding will clarify the often somewhat crude accounts given in criminal law dogmatics (case law and textbooks) of actus reus and mens rea , accounts which often fail to distinguish been action as a physically or conventionally demarcated chunk of behavior and action as the carrying out of the choice of an option, that is of a proposal shaped and thus given a privileged description in the deliberations of the acting subject. The difference between intended or chosen means (or ends) and foreseeable or even fully foreseen effects (“side-effects”), like the consequent difference between the moral and, presumptively, legal standards applicable respectively to intended and not-intended effects, is psychologically and morally real. But it is often distorted by a simplistic legal dogmatics too averse to the (very real) risk that defendants will prevaricate about what they had in mind. What counts, and can often be inferred despite prevarication, is the act-description under which the behavior chosen was attractive to the defendant in his or her actual deliberations (as distinct from rationalizing act-descriptions adopted to present that motivation in a better light).

The reality of intention in the distinct but related field of communication of meaning will also be explored and defended by a natural law theory of law. This does not involve an unqualified and simple originalism in constitutional interpretation, or a simple denial of the characteristic insistence of legal dogmatics that the intention of the parties to agreements or declarations is to be ascertained “objectively (not subjectively),” that is, by reference to what a reasonable observer would have taken the statement in issue to mean. For: such an observer (and thus the “objective” viewpoint) will presumptively have given primacy in this interpretation to what (as far as the observer can discern in the circumstances of the statement’s making [= utterance]) the statement’s author actually (“subjectively”) meant (= intended to express/state).

Criminal responsibility (guilt) is primarily for acts and consequences intended by the offender. Liability for negligence is relatively exceptional in modern criminal law, though the predominant form of liability in modern law of compensation (“civil law”). (The duties and standards of care used to attribute tortious/delictual/civil liability are in part straightforwardly moral and in part conventional—in neither part are they securely source-based in the sense of sources given unconditional primacy in legal positivism.)

The legal enunciation of rules of criminal law (mostly “prohibitions”) has as its primary goal the elimination or at least discouraging of the specified kinds of action (or omission). In this phase of the legal institution of criminal law and punishment, the goal can be called deterrence. The fact that this goal works partly by enforcement and application of the threatened sanction in the event of violation and conviction does not, however, entail that deterrence is the formative or even the primary end of punishment. Indeed, the institution of punishment has its primary sense and justification, not in deterrence, but in the restoration of that presumptively fair balance of burdens and advantages which offenders upset, precisely in choosing to prefer their own purposes and advantage to restraining their action so as to avoid violating the law. In preferring that self-preferential option, offenders help themselves to an advantage over all who do restrain themselves so as to respect the law. The offenders thereby upset the presumptively fair balance of advantages and burdens between themselves and the law-abiding. The primary purpose of punishment thus can reasonably be to restore that disturbed balance by depriving convicted offenders of their unfairly gained advantage—excess freedom of action—by imposing upon them measures, punishments, whose precise purpose is to restrict their freedom of action, whether by fines or imprisonment, proportionately to the degree to which they indulged their self-preference. Punishment in that way seeks to ensure that, over the span of time running from before the offence to the undergoing of the penalty, no one gains an advantage over fellow citizens by offending.

Thus, while compensation in civil law (tort, delict, etc.) rectifies the disturbed balance of advantages and burdens as between tortfeasors and their victims , punishment in criminal (penal) law rectifies the relationship between offenders and all the law-abiding members of the community. This retributive justification (general justifying aim) of punishment explains why mental competence and mens rea are standard legal pre-conditions of criminal guilt and liability to punishment. It is compatible with concurrent goals of deterrence, protection and reform, as bonus side-effects of the retributive sentence, and as organizing aims of specific measures and features e.g., of a prison regimen. It both presupposes and reinforces the reality that the political community in question stands to offenders and law-abiding alike as our community .

Examination of (i) how one legal system becomes independent of another by lawful processes and (ii) how parts of a legal system (e.g., its constitution, or its rules for identifying office-holders) are replaced by the unlawful processes of coup d’état or revolution demonstrates (see Raz 1979, 100–109) that the identity of a subsisting legal system as one and the same system of legal norms cannot be explained (or even coherently described) by an account which refers only to the norms and their inter-relationships as validating norms and validated norms. The non-momentary identity of a legal system is a function of the subsisting identity of the community whose legal system it is. Legal theory is sub-alternated to the historical understanding (including self-understanding) of a community and its members as being this community —paradigmatically, this nation-state—rather than some accidental sequence or agglomeration of persons and events, and this understanding must be in some substantial measure non-dependent upon the legal norms that the community may succeed in constituting for itself and its members. Doubtless the shared purpose of living together under a rule of law, and the shared memory of a shared acknowledgment or recognition of such laws as our laws, are normally important components of such a shared understanding of political-communal and legal identity. But other shared purposes, memories and dispositions to act must be also be substantially present, if the phenomena of lawful independence and revolutionary constitutional change are to be as they are.

The not uncritical realism of natural law theory, evidenced in its approach to the realities of intention as distinct from foresight and inattention, and of self-preferential choice and the differing relationships between (i) offender and law-abiding and (ii) tortfeasor and victim, similarly enables it to undertake a critical reflection, within legal theory broadly understood, on the kinds of community capable of sustaining and being ordered in part by a legal system.

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• –––, 1995, Ethics in the Public Domain , Oxford: Clarendon Press.
• –––, 2009, Between Authority and Interpretation: On the Theory of Law & Practical Reason , Oxford: Oxford University Press.
• Simmonds, N.E., 2004, “Straightforwardly False: The Collapse of Kramer’s Positivism,” Cambridge Law Journal , 63: 98.
• –––, 2005, “Law as a Moral Idea,” University of Toronto Law Journal , 55: 61.
• –––, 2006, “Evil Contingencies and the Rule of Law,” American Journal of Jurisprudence , 51: 179–189
• –––, 2007, Law as a Moral Idea , Oxford: Oxford University Press.
• Soper, Philip, 1992, “Some Natural Misunderstandings about Natural Law,” Michigan Law Review , 90: 2393–2423.

How to cite this entry . Preview the PDF version of this entry at the Friends of the SEP Society . Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO). Enhanced bibliography for this entry at PhilPapers , with links to its database.

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37 Aquinas’s Natural Law Theory

Mark Dimmock and Andrew Fisher, Ethics for A-Level. Cambridge, UK: Open Book Publishers, 2017, https://doi.org/10.11647/OBP.0125

Aquinas’s Natural Law Theory

Grace does not destroy nature but perfects it . 1

They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them. 2

1. Introduction to Aquinas

Thomas Aquinas (1225–1274) was an intellectual and religious revolutionary, living at a time of great philosophical, theological and scientific development. He was a member of the Dominican Friars, which at that time was considered to be a cult, and was taught by one of the greatest intellects of the age, Albert the Great (1208–1280). In a nutshell Aquinas wanted to move away from Plato’s thinking, which was hugely influential at the time, and instead introduce Aristotelian ideas to science, nature and theology.

Aquinas wrote an incredible amount — in fact one of the miracles accredited to him was the amount he wrote! His most famous work is Summa Theologica and this runs to some three and half thousand pages and contains many fascinating and profound insights, such as proofs for God’s existence. The book remained a fundamental basis for Catholic thinking right up to the 1960s! But do not worry we will only be focusing on a few key ideas! Specifically books I–II, questions 93–95.

2. Motivating Natural Law Theory: The Euthyphro Dilemma and Divine Command Theory

The likely answer from a religious person as to why we should not steal, or commit adultery is: “because God forbids us”; or if we ask why we should love our neighbor or give money to charity then the answer is likely to be “because God commands it”. Drawing this link between what is right and wrong and what God commands and forbids is what is called the Divine Command Theory (DCT).

There is a powerful and influential challenge to such an account called the Euthyphro dilemma after the challenge was first raised in Plato’s Euthyphro . The dilemma runs as follows:

Either God commands something is right because it is, or it is right because God commands it. If God commands something because it is right, then God’s commands do not make it right, His commands only tell us what is right. This means God simply drops out of the picture in terms of explaining why something is right.

If on the other hand something is right because God commands it then anything at all could be right; killing children or setting fire to churches could be morally acceptable. But if a moral theory says this then that looks as if the theory is wrong.

Most theists reject the first option and opt for this second option — that God’s commands make something right. But they then have to face the problem that it make morality haphazard. This “ arbitrariness problem ” as it is sometimes called, is the reason that many, including Aquinas, give up on the Divine Command Theory.

So for Aquinas what role, if any at all, does God have when it comes to morality? For him, God’s commands are there to help us to come to see what, as a matter of fact, is right and wrong rather than determine what is right and wrong. That is, Aquinas opts for the first option in the Euthyphro dilemma as stated above. But then this raises the obvious question: if it is not God’s commands that make something right and wrong, then what does? Does not God just fall out of the picture? This is where his Natural Law Theory comes in.

3. Natural Law Theory

Aquinas’s Natural Law Theory contains four different types of law: Eternal Law, Natural Law, Human Law and Divine Law . The way to understand these four laws and how they relate to one another is via the Eternal Law, so we’d better start there…

By “Eternal Law’” Aquinas means God’s rational purpose and plan for all things. And because the Eternal Law is part of God’s mind then it has always, and will always, exist. The Eternal Law is not simply something that God decided at some point to write.

Aquinas thinks that everything has a purpose and follows a plan. He, like Aristotle, is a teleologist (the Greek term “ telos ” refers to what we might call a purpose, goal, end/or the true final function of an object and believes that every object has a telos ; the acorn has the telos of growing into an oak; the eye a telos of seeing; a rat of eating and reproducing etc. If something fulfills its purpose/plan then it is following the Eternal Law.

Aquinas thinks that something is good in as far as it fulfils its purpose/plan. This fits with common sense. A “ good ” eye is one which sees well, an acorn is a good if it grows into a strong oak tree.

But what about humans? Just as a good eye is to see, and a good acorn is to grow then a good human is to…? Is to what? How are we going to finish this sentence? What do you think?

Aquinas thinks that the answer is reason and that it is this that makes us distinct from rats and rocks. What is right for me and you as humans is to act according to reason. If we act according to reason then we are partaking in the Natural Law .

If we all act according to reason, then we will all agree to some overarching general rules (what Aquinas calls primary precepts ). These are absolute and binding on all rational agents and because of this Aquinas rejects relativism .

The first primary precept is that good is to be pursued and done and evil avoided. He thinks that this is the guiding principle for all our decision making.

Before unpacking this, it is worth clarifying something about what “law” means. Imagine that we are playing Cluedo and we are trying to work out the identity of the murderer. There are certain rules about how to move around the board, how to deal out cards, how to reveal the murderer etc. These rules are all written down and can be consulted.

However, in playing the game there are other rules that operate which are so obvious that they are neither written down nor spoken. One such rule is that a claim made in the game cannot both be true and false; if it is Professor Plum who is the murderer then it cannot be true that it is not Professor Plum who is the murderer. These are internal rules which any rational person can come to recognize by simply thinking and are not external like the other rules — such as you can only have one guess as to the identity of the murderer. When Aquinas talks of Natural Laws, he means internal rules and not external ones .

Natural Law does not generate an external set of rules that are written down for us to consult but rather it generates general rules that any rational agent can come to recognize simply in virtue of being rational. For example, for Aquinas it is not as if we need to check whether we should pursue good and avoid evil, as it is just part of how we already think about things. Aquinas gives some more examples of primary precepts:

• Protect and preserve human life.
• Reproduce and educate one’s offspring.
• Know and worship God.
• Live in a society .

These precepts are primary because they are true for all people in all instances and are consistent with Natural Law.

Aquinas also introduces what he calls the Human Law which gives rise to what he calls “ Secondary Precepts ”. These might include such things as do not drive above 70 mph on a motorway, do not kidnap people, always wear a helmet when riding a bike, do not hack into someone’s bank account. Secondary precepts are not generated by our reason but rather they are imposed by governments, groups, clubs, societies etc.

It is not always morally acceptable to follow secondary precepts. It is only morally acceptable if they are consistent with the Natural Law. If they are, then we ought to follow them, if they are not, then we ought not. To see why think through an example.

Consider the secondary precept that “ if you are a woman and you live in Saudi Arabia then you are not allowed to drive ”. Aquinas would argue that this secondary precept is practically irrational because it treats people differently based on an arbitrary difference (gender). He would reason that if the men in power in Saudi actually really thought hard then they too would recognize that this law is morally wrong. This in turn means that Aquinas would think that this human law does not fit with the Natural Law. Hence, it is morally wrong to follow a law that says that men can, and women cannot, drive. So although it is presented as a secondary precept, because it is not in accordance with Natural Law, it is what Aquinas calls an apparent good . This is in contrast with those secondary precepts which are in accordance with the Natural Law and which he calls the real goods .

Unlike primary precepts, Aquinas is not committed to there being only one set of secondary precepts for all people in all situations. It is consistent with Aquinas’s thinking to have a law to drive on the right in the US and on the left in the UK as there is no practical reason to think that there is one correct side of the road on which to drive.

It is clear that on our own we are not very good at discovering primary precepts and consequently Aquinas thinks that what we ought to do is talk and interact with people. To discover our real goods — our secondary precepts which accord with Natural Law — we need to be part of a society. For example, we might think that “treat Christians as secondary citizens” is a good secondary precept until we talk and live with Christians. The more we can think and talk with others in society the better and it is for this reason that “live in society” is itself a primary precept.

But looking at what we have said already about Natural Laws and primary and secondary precepts, we might think that there is no need for God. If we can learn these primary precepts by rational reflection then God simply drops out of the story (recall the Euthyphro dilemma above).

Just to recap as there a lots of moving parts to the story. We now have Eternal Law (God’s plans/purpose for all things), Natural Laws (our partaking in the Eternal Law which leads to primary precepts), Human Laws (humans making specific laws to capture the truths of the Natural Laws which lead to secondary precepts) and now finally Aquinas introduces the Divine Law .

The Divine Law, which is discovered through revelation , should be thought of as the Divine equivalent of the Human Law (those discovered through rational reflection and created by people). Divine laws are those that God has, in His grace, seen fit to give us and are those “mysteries”, those rules given by God which we find in scripture; for example, the ten commandments. But why introduce the Divine Law at all? It certainly feels we have enough Laws. Here is a story to illustrate Aquinas’s answer.

A number of years ago I was talking to a minister of a church. He told me about an instance where a married man came to ask his advice about whether to finish an affair he was having. The man’s reasoning went as follows — “I am having an affair which just feels so right, we are both very much in love and surely God would want what is best for me! How could it be wrong if we are so happy?”

In response, the minister opened the Bible to the Ten Commandments and pointed out the commandment that it says that it is wrong to commit adultery. Case closed. The point of this story is simple. We can be confused and mistaken about what we think we have most reason to do and because of this we need someone who actually knows the mind of God to guide us, and who better to know this than God Himself. This then is precisely what is revealed in the Divine Law.

Or consider another example. We recognize that we find it hard to forgive our friends and nearly always impossible to forgive our enemies. We tell ourselves we have the right to be angry, to bear grudges, etc. Isn’t this just human? However, these human reasons are distortions of the Eternal Law. We need some guidance when it comes to forgiveness and it is where the Divine Law which tells us that we should forgive others — including our enemies. Following the Human Laws and the Divine Laws will help us to fulfill our purposes and plans and be truly happy.

4. Summary of Aquinas’s Natural Law Theory

For Aquinas everything has a function (a telos ) and the good thing(s) to do are those acts that fulfill that function. Some things such as acorns, and eyes, just do that naturally. However, humans are free and hence need guidance to find the right path. That right path is found through reasoning and generates the “internal” Natural Law. By following the Natural Law we participate in God’s purpose for us in the Eternal Law.

However, the primary precepts that derive from the Natural Law are quite general, such as, pursue good and shun evil . So we need to create secondary precepts which can actually guide our day-to-day behavior. But we are fallible so sometimes we get these secondary precepts wrong, sometimes we get them right. When they are wrong they only reflect our apparent goods. When they are right they reflect our real goods.

Finally, however good we are because we are finite and sinful, we can only get so far with rational reflection. We need some revealed guidance and this comes in the form of Divine Law. So to return to the Euthyphro dilemma. God’s commands through the Divine Law are ways of illuminating what is in fact morally acceptable and not what determines what is morally acceptable. Aquinas rejects the Divine Command Theory.

5. Putting this into Practice: The Doctrine of Double Effect (DDE)

Let’s consider some examples to show that what we have said so far might actually work. Imagine someone considering suicide. Is this morally acceptable or not? Recall, it is part of the Natural Law to preserve and protect human life. Clearly suicide is not preserving and protecting human life. It is therefore irrational to kill oneself and cannot be part of God’s plan for our life; hence it is morally unacceptable.

Imagine that someone is considering having an abortion after becoming pregnant due to rape. The same reasoning is going to apply. We ought to preserve and protect human life and hence an abortion in this case is morally wrong.

However, as we will see, Aquinas thinks that there are some instances where it is morally acceptable to kill an innocent person and therefore there may be occasions when it is morally acceptable to kill a fetus. But how can this be correct? Will this not violate the primary precept about preserving life? The answer is to understand that for Aquinas, an action is not just about what we do externally but is also about what we do internally (i.e. our motivations). With this distinction he can show that, for example, killing an innocent can be morally acceptable.

To make this clear, Aquinas introduces one of his most famous ideas: the “ Doctrine of Double Effect ”. Let’s see how this works.

Imagine a child brought up in a physically, sexually and emotionally abusive family. He is frequently scared for his life and is locked in the house for days at a time. One day when his father is drunk and ready to abuse him again he quickly grabs a kitchen knife and slashes his father’s artery. His father bleeds out and dies in a matter of minutes. Do you think the son did anything wrong?

Many people would say that he did nothing morally wrong and in fact, some might even go as far as to say that he should get a pat on the back for his actions. What about Aquinas? What would he say?

We might think that given the Natural Law to “preserve and protect life” he would say that this action is morally wrong. But, in fact, he would say the son’s action was not morally wrong (Aquinas discusses self-defense in the Summa Theologica (II–II, Qu. 64)).

So why is the son killing the father not in direct contradiction with the primary precept? Aquinas asks us to consider the difference between the external act — the fact that the father was killed, and the internal act — the motive.

In our example, the action is one of self-defense because of the son’s internal action and because of this, Aquinas would think the killing is morally acceptable. This distinction and conclusion is possible because of Aquinas’s Doctrine of Double Effect which states that if an act fulfills four conditions then it is morally acceptable. If not, then it is not.

• The first principle is that the act must be a good one.
• The second principle is that the act must come about before the consequences.
• The third is that the intention must be good.
• The fourth, it must be for serious reasons.

This is abstract so let’s go back to our example. The act of the son was performed to save his own life so that is good — we can tick (1). Moreover, the act to save his life came about first — we can tick (2). The son did not first act to kill his father in order to save his own life. That would be doing evil to bring about good and that is never morally acceptable. The intention of the son was to preserve and protect his life, so the intention was good — tick (3). Finally, the reasons were serious as it was his life or his father’s life — tick (4).

So given that the act meets all four principles, it is in line with the DDE and hence the action is morally acceptable , even though it caused someone to die and hence seems contrary to the primary precept of preserving life.

We can draw a contrasting case. Imagine that instead of slashing his father in self-defense, the son plans the killing. He works out the best time, the best day and then sets up a trip wire causing his father to fall from his flat window to his death. Does this action meet the four criteria of the DDE? Well, no, because the son’s intention is to kill the father rather than save his own life —  we must put a cross at (3).

We have already seen that suicide is morally impermissible for Aquinas, so does that mean that any action you take that leads knowingly to your own death is morally wrong? No. Because even though the external act of your own death is the same, the internal act — the intention — might be different. An action is judged via the Natural Law both externally and internally .

Imagine a case where a soldier sees a grenade thrown into her barracks. Knowing that she does not have time to defuse it or throw it away, she throws herself on the grenade. It blows up, killing her but saving other soldiers in her barracks. Is this wrong or right? Aquinas says this is morally acceptable given DDE. If we judge this act both internally and externally we’ll see why.

The intention — the internal act — was not to kill herself even though she could foresee that this was certainly what was going to happen. The act itself is good, to save her fellow soldiers (1). The order is right, she is not doing evil so good will happen (2). The intention is good, it is to save her fellow soldiers (3). The reason is serious, it concerns people’s lives (4).

Contrast this with a soldier who decides to kill herself by blowing herself up. The intention is not good and hence the DDE does not permit this suicidal action.

Finally, imagine that a woman is pregnant and also has inoperable uterine cancer. The doctors have two choices; to take out the uterus and save the mother, but the fetus will die; or leave the fetus to develop and be born healthy, but the woman will die. What would Aquinas say in this instance? Well using the DDE he would say that it is morally acceptable to remove the cancer.

The action is to remove the cancer; it has the foreseeable consequences of the fetus dying but that is not what is intended. The action — to remove the cancer — is good (1). The act of removing the cancer comes before the death of the fetus (2). The intention to save the woman’s life is also good (3). Finally, the reasons are serious as they are about the life and death of the woman and the fetus (4).

So even though this is a case where the doctor’s actions bring about the death of the foetus it would be acceptable for Aquinas through his Natural Law Theory, as is shown via the DDE.

6. Some Thoughts about Natural Law Theory

There are many things we might consider when thinking through Aquinas’s Natural Law Theory. There are some obvious problems we could raise, such as the problem about whether or not God exists. If God does not exist then the Eternal Law does not exist and therefore the whole theory comes tumbling down. However, as good philosophers we ought always to operate with a principle of charity and grant our opponent is rational and give the strongest possible interpretation of their argument. So, let’s assume for the sake of argument that God exists. How plausible is Aquinas’s theory? There are a number of things that we can pick up on.

Aquinas’s theory works on the idea that if something is “natural”, that is, if it fulfills its function, then it is morally acceptable, but there are a number of unanswered questions relating to natural .

We might ask, why does “natural” matter? We can think of things that are not “natural” but which are perfectly acceptable, and things which are natural which are not. For example, wearing clothes, taking medication and body piercing certainly are not natural, but we would not want to say such things are morally wrong.

On the other hand we might consider that violence is a natural response to an unfaithful partner, but also think that such violence is morally unacceptable. So it is not true that we can discover what is morally acceptable or not simply by discovering what is natural and what is not.

Put this worry aside. Recall, Aquinas thinks that reproduction is natural and hence reproduction is morally acceptable. This means that sex that does not lead to reproduction is morally unacceptable. Notice that Aquinas is not saying that if sex does not lead to pregnancy it is wrong. After all, sometimes the timing is not right. His claim is rather that if there is no potential for sex to lead to pregnancy then it is wrong. However, even with this qualification this would mean a whole host of things such as homosexuality and contraception are morally wrong. We might take this as a reason to rethink Aquinas’s moral framework.

There is, though, a more fundamental worry at the heart of this approach (and Aristotle’s) to ethics. Namely, they think that everything has a goal ( telos ). Now, with some things this might be plausible. Things such as the eye or an acorn have a clear function — to grow, to see — but what about humans? This seems a bit less obvious! Do humans (rather than our individual parts) really have a telos ? There are certainly some philosophers — such as the existentialists, for example Simone de Beauvoir (1908–1986) — who think that there is no such thing as human nature and no such thing as a human function or goal. But if we are unconvinced that humans have a goal, then this whole approach to ethics seems flawed.

Next we might raise questions about DDE. Go back to our example about abortion. For Aquinas it is morally acceptable to remove the uterus even if we know that in doing so the fetus will die. What is not morally acceptable is to intend to kill the fetus by removing the uterus. On first reading this seems to makes sense; we have an intuitive feel for what DDE is getting at. However, when we consider it in more detail it is far from clear.

Imagine two doctors who (apparently) do exactly the same thing, they both remove the uterus and the fetus dies. The one intends to take out the uterus — in full knowledge that the fetus will die — the other intends to kill the fetus. For the DDE to work in the way that Aquinas understands it, this difference in intention makes the moral difference between the two doctors. However, is there really a moral difference? To put pressure on the answer that there is, ask yourself what you think it means to intend to do something. If the first doctor says “I did not intend to kill the fetus” can we make sense of this? After all, if you asked her “did you know that in taking out the uterus the fetus would die?” she would say “yes, of course”. But if she did this and the fetus died, did not she intend (in some sense) to kill the fetus? So this issue raises some complex question about the nature of the mind, and how we might understand intentions.

Finally, we might wonder how easy it is to work out what actually to do using the Natural Law. We would hope our moral theory gives us direction in living our lives. That, we might think, is precisely the role of a moral theory. But how might it work in this case?

For Aquinas, if we rationally reflect then we arrive at the right way of proceeding. If this is in line with the Natural Law and the Divine Law then it is morally acceptable. If it is out of line, then it is not. The assumption is that the more we think, the more rational we become, the more convergence there will be. We’ll all start to have similar views on what is right and wrong. But is this too optimistic? Very often, even after extensive reflection and cool deliberation with friends and colleagues, it is not obvious to us what we as rational agents should do. We all know people we take to be rational, but we disagree with them on moral issues. And even in obviously rational areas such as mathematics, the best mathematicians are not able to agree. We might then be skeptical that as rational agents we will come to be in line with the Natural and Divine Laws.

Aquinas is an intellectual giant. He wrote an incredible amount covering a vast array of topics. His influence has been immense. His central idea is that humans are created by God to reason — that is our function. Humans do the morally right thing if we act in accordance with reason, and the morally wrong thing if we don’t.

Aquinas is an incredibly subtle and complex thinker. For example, his Doctrine of Double Effect makes us to reflect on what we actually mean by “actions”, “intentions” and “consequences”. His work remains much discussed and researched and typically still plays a central role in a Christian Ethics that rejects Divine Command Theory.

KEY TERMINOLOGY

Apparent goods

A posteriori

Eternal Law

External acts

Natural Law

Primary precepts

Secondary precepts

Internal acts

Doctrine of Double Effect

Aquinas, Thomas, Summa Theologica , *freely available at https://ccel.org/ccel/aquinas/summa.pdf

―,  Romans ( Commentary on the Letter of Saint Paul to the Romans )

Plato, Euthyphro , translated by Benjamin Jowett, freely available at http://classics.mit.edu/Plato/euthyfro.html

1 T. Aquinas, Summa Theologica , I, I:8,* https://ccel.org/ccel/aquinas/summa.pdf

2 T. Aquinas, Romans , 2:15.

*Update to link to source was made because the original source contained a dead link.

Aquinas’s Natural Law Theory Copyright © 2020 by Mark Dimmock and Andrew Fisher, Ethics for A-Level. Cambridge, UK: Open Book Publishers, 2017, https://doi.org/10.11647/OBP.0125 is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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Natural Law

[This article was co-authored by Robert P. George and Christopher Tollefsen.]

Natural law ethics forms a distinctive family of ethical theories, all of which take the human good, or human well-being, as central to their theoretical approach. After a period of diminishing influence following the Enlightenment, during which natural law theory was largely a matter for Catholic seminaries, natural ethics has seen a resurgence in recent decades in normative ethics, philosophy of law, political theory, and applied ethics.

Continue reading in the International Encyclopedia of Ethics.

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Natural Law: Definition and Application

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Natural law is a theory that says all humans inherit—perhaps through a divine presence—a universal set of moral rules that govern human conduct.

Key Takeaways: Natural Law

• Natural law theory holds that all human conduct is governed by an inherited set of universal moral rules. These rules apply to everyone, everywhere, in the same way.
• As a philosophy, natural law deals with moral questions of “right vs. wrong,” and assumes that all people want to live “good and innocent” lives.
• Natural law is the opposite of “man-made” or “positive” law enacted by courts or governments.
• Under natural law, taking another life is forbidden, no matter the circumstances involved, including self-defense.

Natural law exists independently of regular or “positive” laws—laws enacted by courts or governments. Historically, the philosophy of natural law has dealt with the timeless question of “right vs. wrong” in determining the proper human behavior. First referred to in the Bible, the concept of natural law was later addressed by the ancient Greek philosopher Aristotle and Roman philosopher Cicero . 

What Is Natural Law?

Natural law is a philosophy based on the idea that everyone in a given society shares the same idea of what constitutes “right” and “wrong.” Further, natural law assumes that all people want to live “good and innocent” lives. Thus, natural law can also be thought of as the basis of “morality.” 

Natural law is the opposite of “man-made” or “positive” law. While positive law may be inspired by natural law, natural law may not be inspired by positive law. For example, laws against impaired driving are positive laws inspired by natural laws.

Unlike laws enacted by governments to address specific needs or behaviors, natural law is universal, applying to everyone, everywhere, in the same way. For example, natural law assumes that everyone believes killing another person is wrong and that punishment for killing another person is right. 

Natural Law and Self Defense

In regular law, the concept of self-defense is often used as justification for killing an aggressor. Under natural law, however, self-defense has no place. Taking another life is forbidden under natural law, no matter the circumstances involved. Even in the case of an armed person breaking into another person’s home, natural law still forbids the homeowner from killing that person in self-defense. In this way, natural law differs from government-enacted self-defense laws like so-called “ Castle Doctrine ” laws. 

Natural Rights vs. Human Rights

Integral to the theory of natural law, natural rights are rights endowed by birth and not dependent on the laws or customs of any particular culture or government. As stated in the United States Declaration of Independence , for example, the natural rights mentioned are “Life, Liberty, and the Pursuit of Happiness.” In this manner, natural rights are considered universal and inalienable, meaning they cannot be repealed by human laws.

Human rights, in contrast, are rights endowed by society, such as the right to live in safe dwellings in safe communities, the right to healthy food and water, and the right to receive healthcare. In many modern countries, citizens believe the government should help provide these basic needs to people who have difficulty obtaining them on their own. In mainly socialist societies , citizens believe the government should provide such needs to all people, regardless of their ability to obtain them.

Natural Law in the US Legal System

The American legal system is based on the theory of natural law holding that the main goal of all people is to live a “good, peaceful, and happy” life, and that circumstances preventing them from doing so are “immoral” and should be eliminated. In this context, natural law, human rights, and morality are inseparably intertwined in the American legal system. 

Natural law theorists contend that laws created by the government should be motivated by morality. In asking the government to enact laws, the people strive to enforce their collective concept of what is right and wrong. For example, the Civil Rights Act of 1964 was enacted to right what the people considered to be a moral wrong—racial discrimination. Similarly, the peoples’ view of enslavement as being a denial of human rights led to ratification of the Fourteenth Amendment in 1868. 

Natural Law in the Foundations of American Justice

Governments do not grant natural rights. Instead, through covenants like the American Declaration of Independence and the U.S. Constitution , governments create a legal framework under which the people are permitted to exercise their natural rights. In return, people are expected to live according to that framework.

In his 1991 Senate confirmation hearing, U.S. Supreme Court Justice Clarence Thomas expressed the widely shared belief that the Supreme Court should refer to natural law in interpreting the Constitution. “We look at natural law beliefs of the Founders as a background to our Constitution,” he stated. 

Among the Founders who inspired Justice Thomas in considering natural law to be an integral part of the American justice system, Thomas Jefferson referred to it when he wrote in the first paragraph of the Declaration of Independence:

“When, in the course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the laws of nature and of nature’s God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.”

Jefferson then reinforced the concept that governments cannot deny rights granted by natural law in the famous phrase: 

“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.” 

Natural Law in Practice: Hobby Lobby vs. Obamacare

Deeply rooted in the Bible, natural law theory often influences actual legal cases involving religion. An example can be found in the 2014 case of Burwell v. Hobby Lobby Stores , in which the U.S. Supreme Court ruled that for-profit companies are not legally obligated to provide employee health care insurance that covers expenses for services that go against their religious beliefs.

The Patient Protection and Affordable Care Act of 2010 —better known as “Obamacare”—requires employer-provided group health care plans to cover certain types of preventative care, including FDA-approved contraceptive methods. This requirement conflicted with the religious beliefs of the Green family, owners of Hobby Lobby Stores, Inc., a nationwide chain of arts and crafts stores. The Green family had organized Hobby Lobby around their Christian principles and had repeatedly stated their desire to operate the business according to Biblical doctrine, including the belief that any use of contraception is immoral. 

In 2012, the Greens sued the U.S. Department of Health and Human Services, claiming that the Affordable Care Act’s requirement that employment-based group health care plans cover contraception violated the Free Exercise of Religion Clause of the First Amendment and the 1993 Religious Freedom Restoration Act (RFRA), that “ensures that interests in religious freedom are protected.” Under the Affordable Care Act, Hobby Lobby faced significant fines if its employee health care plan failed to pay for contraceptive services.

In considering the case, the Supreme Court was asked to decide if the RFRA allowed closely held, for-profit companies to refuse to provide its employees with health insurance coverage for contraception based on the religious objections of the company’s owners. 

In a 5-4 decision, the Supreme Court held that by forcing religion-based companies to fund what they consider the immoral act of abortion, the Affordable Care Act placed an unconstitutionally “substantial burden” on those companies. The court further ruled that an existing provision in the Affordable Care Act exempting non-profit religious organizations from providing contraception coverage should also apply to for-profit corporations such as Hobby Lobby.

The landmark Hobby Lobby decision marked the first time the Supreme Court had recognized and upheld a for-profit corporation’s natural law claim of protection based on a religious belief.

Sources and Further Reference

• “ Natural Law .” Internet Encyclopedia of Philosophy
• “ The Natural Law Tradition in Ethics .” Stanford Encyclopedia of Philosophy (2002-2019)
• “Hearing of the Senate Judiciary Committee on the Nomination of Clarence Thomas to the Supreme Court. Part 1 , Part 2 , Part 3 , Part 4 .” U.S. Government Publishing Office.
• What Is Parens Patriae? Definition and Examples
• What Is Statutory Law? Definition and Examples
• What Is Civil Law? Definition and Examples
• What Is Qualified Immunity? Definition and Examples
• What Is a Writ of Certiorari?
• What Is Judicial Restraint? Definition and Examples
• What Is Sedition? Definition and Examples
• Obergefell v. Hodges: Supreme Court Case, Arguments, Impacts
• What Is Administrative Law? Definition and Examples
• What Is a Protected Class?
• The Warren Court: Its Impact and Importance
• What Is Corporal Punishment? Is It Still Allowed?
• What Is Identity Theft? Definition, Laws, and Prevention
• What Is Originalism? Definition and Examples
• What Is an Amicus Brief?
• Court Case of Korematsu v. United States

A Level Philosophy & Religious Studies

Natural Law summary notes

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Aquinas’ Natural law ethics AO1

• Aquinas claimed there are four tiers of law:
• Eternal law – God’s mind and omnibenevolent plan for the universe – this is beyond our understanding.
• Divine law – the bible
• Natural law – the orientation towards the good built into our nature by God
• Human law – the laws we make (which should follow the natural & divine law).
• Telos – our purpose is to glorify God by following the primary precepts of natural law.
• This telos is built by God into our nature because Aquinas thinks we are all born with an ability called synderesis – the ability to know first the synderesis rule – to do good and avoid evil – and then the primary precepts of natural law: 
• Preserve human life, reproduce, educate, orderly society, worship God.
• We then apply the primary precepts to moral actions/situations and get a secondary precept – a judgement on that particular action/situation. This process is called conscientia.
• E.g. euthanasia goes against the primary precept to preserve human life – therefore ‘euthanasia is wrong’ would be a secondary precept.
• Double effect. Some actions have two effects – one that goes against the primary precepts, and one that fits with them. 
• E.g. killing someone in self-defence – one effect is killing someone, but the other effect is saving your life.
• Aquinas says in situations like this, it is morally acceptable so long as you intended to bring about the good effect and the bad effect was beside your intention.
• There must also be proportionality – e.g. if you use more force than is necessary then that’s no longer acceptable.
• The traditional Catholic approach adds some further conditions:
• There is also a condition that the bad effect not be an intrinsic evil – like killing an innocent person or adultery.

Whether Natural law is outdated

• J S Mill says the divine law of the bible – especially old testament – was clearly only relevant in an ancient more barbaric time.
• Mill’s argument can also be applied to Natural law ethics.
• It was created in a mediaeval socio-economic time and its rules reflect that. 
• In Aquinas’ time, having sex outside marriage was often a death sentence because sex led to children, and single mothers struggled to survive. There was a great need for reproduction, because so many children died – which was part of why it was against homosexuality, because of the intense need for reproduction. Homosexuality was also seen as against the nuclear family dynamic, which was also needed for reproduction and education.
• There was around 60-70 times the murder rate in Aquinas time, showing the clear need for really strict rules against killing – which is why being against euthanasia made sense then.
• Today, these socio-economic conditions are no longer present. We now have effective contraception and support for single parents. We have overpopulation, and it’s no longer the case that children outside marriage are doomed to lack education. 
• The reasoning behind Aquinas’ views on the primary precepts, including their application to euthanasia and sexual ethics, no longer apply. 
• It is outdated. In Aquinas’ time, his reasoning made sense – but that was because of the dire situation society was in.
• outdated doesn’t mean wrong – it just means popular opinion has shifted.
• If Hitler had won WW2, democracy would have come to be seen as ‘outdated’.

evaluation:

• However – the Critique is not just that Aquinas is outdated in that popular opinion has changed – the best version of the ‘outdated’ critique is to argue that Aquinas’ theory was actually a reaction to his socio-economic context and since that has changed, Natural law is no longer relevant.
• Aquinas thought that he discovered the primary precepts through human reason, as God designed. However, arguably it’s a simpler explanation that Aquinas was simply figuring out what would have been good for people in his socio-economic condition. That the resulting principles actually came from God was only in his imagination.

Modern science’s rejection of final causation (telos)

• There’s no scientific evidence for purpose/telos – science can explain everything in the universe, or is at least progressing towards explaining everything, without needing the concept of ‘purpose/telos’. 
• At the beginning of the enlightenment period, scientist Francis Bacon claimed that the concept of ‘telos’ was unscientific.
• The modern scientific view is that the universe is just composed of atoms and energy in fields of force. There is no space in our scientific understanding of the universe for anything like purpose or telos to exist.
• Physicist Sean Carroll concludes purpose is not built into the ‘architecture’ of the universe.
• Telos looks like an outdated unscientific term that people just project onto reality.
• Aristotle said an acorn must have the telos of growing into an oak tree. But we now understand thanks to modern science that this can be explained purely through material and efficient causation – the DNA of acorn.
• Similarly, human nature might behaviourally orient us, but this too can be explained by evolution.
• Evolution in a herd species will generate instincts like empathy. These are not intrinsically ‘moral’ behaviours from a God, they are just what were evolutionarily advantageous to our species. 
• So again, science can explain everything about us without the need for the concept of telos – making it an unscientific concept.
• Human nature is not the result of anything God-given like telos.
• Purpose is nonetheless an important part of human life.
• Polkinghorne argues that science can explain the ‘what’ but not the ‘why’. Science investigates what is true of the universe. Polkinghorne claims we do need the concept of purpose, to explain why the universe exists in the way it does. Science can’t explain that.
• Max Tegmark argues one day scientists might actually explain why the universe exists. This would reduce the ‘why’ to non-teleological scientific concepts.
• Or, Russell could be right that there is no ‘why’, the universe could be a brute fact. Dawkins develops this point. Just because it’s possible to ask the question ‘why’, that doesn’t mean there actually is a why.
• Either way, we have no basis for thinking telos exists nor any need for it as an explanation.
• So, purpose only exists in people’s minds.
• This critique of Aquinas is successful because of the clear power of science. 
• Science has transformed our world through its immense explanatory power. Although it cannot absolutely disprove telos, it does show that we have no reason to believe that telos exists. Ockham’s razor further justifies this approach. We are justified in believing the simpler explanation that works. If we have a scientific explanation it is simpler than those which require supernatural beings.
• Aquinas’ theory fails – scientific approaches are better explanations.

Natural law ethics & Cross-cultural moral variation

• Fletcher argues a weakness of Aquinas’ approach is cross-cultural moral differences. 
• Aquinas claimed that conscience involves the ability of reason to know the primary precepts, to guide us towards our good end (telos). But if that was true, it should be universally true of all humans regardless of their culture. We would expect to find more moral agreement.
• Different cultures have different moral views – e.g. some countries are more religious and thus ban euthanasia, but other countries allow euthanasia. 
• Not only is there disagreement, it tends to fall along cultural boundaries. Culture and social conditioning is therefore the better explanation of what determines our moral compass, not telos. This was the view of psychologists like Freud and Skinner. Their scientific approach looks stronger than Aquinas’.
• Aquinas would disagree – he would say that even though there’s disagreement there is still a core set of moral views all cultures share which is very similar to the primary precepts.. 
• Everyone agrees that killing for no reason is wrong, everyone agrees an orderly society is good, reproduction is good, education is good. 
• Moral disagreement could just be the result of sinful and corrupt cultures and original sin.

Evaluation 

• However, we have other, better, more scientific explanations of the core moral views found in all cultures. 
• Richard Dawkins argued our moral sense partly came from evolution – which programmed us with empathy to care about other people, reproduce, educate, etc, all of which is evolutionarily advantageous for a herd species like us. 
• Furthermore, there is just a practical requirement for a society to exist. Imagine a culture started allowing killing and stealing – it would fall apart and end. So no special explanation of cross-cultural moral codes is needed.
• Conscience isn’t God’s design directing us towards our telos then. It’s from evolution, social conditioning and social practicality.
• Aquinas’ supernatural explanation of explain cross-cultural moral agreement is an unnecessary hypothesis.
• Aquinas’ whole theory of natural law is better explained by scientific analysis of the nature and nurture that goes into human moral decision making.
• Freud’s scientific approach is a simpler and better explanation of our moral compass than Aquinas’ theological approach.
• So, we do not need the idea of natural law built into us by a God as our telos. That is an unnecessary hypothesis.

Aquinas’ Natural theology vs Karl Barth’s protestant critique

• A strength of Aquinas’ moral theory is its foundation in natural theology.
• In Romans, St Paul comments that the law of God is written on the heart of every human, even those who have never heard of God.
• This supports Aquinas’ proposal of a natural law in addition to the divine law.
• It is also logical for Aquinas to explain this through Aristotle’s concept of telos – that every being’s nature is orientated towards its good end.
• Karl Barth – rejected natural theology as placing a dangerous overreliance on human reason.
• Reason is corrupted by original sin. Original sin might not have totally destroyed reason, but it does make it unreliable. 
• “The finite has no capacity for the infinite”.
• Our finite minds have no – zero – capacity to understand God’s infinite nature.
• So, we should not use reason to know God.
• If we make a mistake when trying to use reason to know God, then we will gain a false view of God and could end up worshipping the wrong thing – perhaps even worshipping something earthly – which is idolatry. This is dangerous as it can lead to the worship of human things like nations, fatherlands, and that he argued contributed to Nazism.
• Barth concluded we should solely rely on faith in the Bible.

Evaluation:

• Barth’s argument is unsuccessful because Aquinas isn’t saying reason can grasp God’s infinite being.
• With natural law, reason isn’t grasping God’s infinite eternal law – just the lesser natural law within our nature.
• Through reason we can also know that God has a quality of love/power/knowledge which is analogous to ours yet proportionally greater than our own.
• Aquinas’ approach is successful because he takes care not to claim too much about God based on reason.
• Reason may sometimes indeed be corrupted, but that doesn’t mean it will always be corrupted. Sometimes, with God’s grace, human reason is capable of knowing something about God.

Proportionalism & the double effect

• Proportionalists like B. Hoose argued that the double effect didn’t make natural law flexible enough.
• Their argument is that God designed the natural law and our telos within the garden of Eden. This means it only functions in our pre-lapsarian state. Back then, following the natural law perfectly enabled flourishing.
• In this fallen world, acting on the primary precepts can actually be disabling of flourishing because of the presence of ontic evil (whatever inhibits flourishing, like suffering).
• Proportionalists conclude that following natural law is valid, but if an action causes a greater balance of ontic good (enables flourishing) compared to ontic evil then it is morally justified – even if it goes against the primary precepts.
• This gives the double effect much more flexibility and would even allow acts previously condemned as intrinsically immoral like killing innocents.
• Pope John Paul II rejected proportionalism, arguing it is an invalid development of true natural law ethics.
• He argues that the point of natural law is our intentional alignment with God’s moral law. That is our telos.
• Proportionalism forgets that our true telos is to follow God, not to secure our happiness, nor even our lives.
• Following God’s moral law is more important than enabling our flourishing. In fact, doing intrinsically evil acts corrupts our alignment with God. JP2 points to the example of Christian martyrs who died for their faith. It is better to die than do something evil. 
• Proportionalism misunderstands the point of Christian ethics, which is to follow God’s moral law.
• JP2 has a point. The very concept of accusing Christian ethics as ‘inflexibile’ misunderstands it. If God has decreed certain laws, then it is right for us to follow them, no matter what happens to us.
• However, the proportionalists also have a point that flourishing was meant to be a component of following the natural law – as Aquinas said.
• Furthermore – consider Fletcher’s case of the family faced with the choice of killing their crying baby or all being discovered by bandits who would kill them all, including the baby, if discovered.
• JP2 has selected a self-serving example of the christian martyrs. Sacrificing oneself for the sake of others is valid in Christianity, as shown by the example of Jesus. 
• However, in Fletcher’s example, if we do not kill the baby – we would be sacrificing other people (the other family members), including other children, not just yourself, simply to do the ‘right’ thing by all dying. Is it really ok to get your other kids killed, just because you wouldn’t kill one of them?
• This is a terrible moral choice, but it does show the limits of traditional natural law ethics. 
• The presence of ontic evil in our fallen world is relevant to the moral situation in a way that John Paul II did not adequately address.

Thomistic Philosophy Page

Natural Law

St. Thomas Aquinas on the Natural Law.

After his Five Ways of Proving the Existence of God ( ST Ia, 2, 3 ), St. Thomas Aquinas is probably most famous for articulating a concise but robust understanding of natural law. Just as he claims and demonstrates in his proofs for God’s existence that natural human reason can come to some understanding of the Author of nature, so in his exposition of natural law, Aquinas shows that human beings can discover objective moral norms by reasoning from the objective order in nature, specifically human nature. While Aquinas believes that this objective order of nature (and the operation of human reason which discovers it) are, in fact, ultimately grounded and established by God’s intelligent willing of the good of creation (i.e., His love), Aquinas’s understands that one need not know that God’s providence underpins the objective order of nature. Thus, whether or not one believes in or rationally proves there is a God, one can recognize and be bound by the natural law for, according to Aquinas, it applies to all people at all times, and in some sense is known by all rational humans (though, of course, they do not (but should) always act in accordance with it).

Eternal Law

In his monumental Summa Theologiae , St. Thomas Aquinas , devotes relatively little space to the natural law – merely a single question and passing mention in two others. There, he bases his doctrine of the natural law, as one would expect, on his understanding of God and His relation to His creation. He grounds his theory of natural law in the notion of an eternal law (in God). In asking whether there is an eternal law, he begins by stating a general definition of all law: Law is a dictate of reason from the ruler for the community he rules.

This dictate of reason is first and foremost within the reason or intellect of the ruler. It is the idea of what should be done to ensure the well-ordered functioning of whatever community the ruler has care for. (It is a fundamental tenet of Aquinas’ political theory that rulers rule for the sake of the governed, i.e., for the good and well-being of those subject to the ruler.) Since he has elsewhere shown that God rules the world with his reason (since he is the cause of its being (cf.  Summa Theologiae I 22, 1-2) ), Aquinas concludes that God has in His intellect an idea by which He governs the world. This Idea, in God, for the governance of things is the eternal law.  ( ST I-II, 91, 1)

Defining the Natural Law

Next, Aquinas asks whether there is in us a natural law. First, he makes a distinction: A law is not only in the reason of a ruler, but may also be in the thing that is ruled. Just as the plan or rule for constructing a house resides primarily in the mind of an architect, so that plan or rule can be said also to be in the house so constructed, imprinted, as it were, into the very composition of the house and dictating how the house is properly to operate or function (cf. ST I-II, 93, 1 ).

In the case of the eternal law, the things of creation that are ruled by that law have it imprinted on the them through their nature or essence. Since things act according to their nature, they derive their “respective inclinations to their proper acts and ends” ( final cause ) according to the law that is written into their nature. Everything in nature, insofar as they reflect the order by which God directs them through their nature for their own benefit, reflects the eternal law in their own natures  ( ST  I-II, 91, 2)

The natural law is properly applied to the case of human beings, and acquires greater precision because of the fact that we have reason and free will . It is our nature as humans to act freely (i.e., to be provident for ourselves and others) by directing ourselves toward our proper acts and end. That is, we human beings must exercise our natural reason to discover what is best for us in order to achieve the end to which our nature inclines. Furthermore, we must do this through the exercise our freedom, by choosing what reason determines to be naturally suited to us, i.e., what is best for our nature.

Now among all others, the rational creature is subject to Divine providence in the most excellent way, in so far as it partakes of a share of providence, by being provident both for itself and for others. Wherefore it has a share of the Eternal Reason, whereby it has a natural inclination to its proper act and end: and this participation of the eternal law in the rational creature is called the natural law . ( ST  I-II, 91, 2)

The natural inclination of humans to achieve their proper end through reason and free will is the natural law. Formally defined, the natural law is humans’ participation in the eternal law, through reason and will. Humans actively participate in the eternal law of God (the governance of the world) by using reason in conformity with the natural law to discern what is good and evil . Just as the proper functioning of the body and its organs in order to achieve an optimal physical life defines health and the rules of medicine and healthy living, so the proper functioning of all human faculties defines the human good and the rules for living well (morally, spiritually, socially, etc.). The natural law encompasses the rules and precepts by which humans do good actions and live well, individually and collectively.

The Human Good

In applying this universal notion of natural law to the human person, one first must decide what it is that (God has ordained) human nature is inclined toward. Since each thing has a nature (given it by God), and each thing has a natural end, so there is a fulfillment to human activity of living. Even apart from knowing about this dependence on God, one can discover by reason what the purpose of living is, and so he or she will discover what his or her natural end is. Building on the insight of Aristotle that “happiness is what all desire,” a person can conclude that they will be happy when he or she achieves this natural end, specifically “a life of virtuous activity in accordance with reason” ( Nicomachean Ethics , I, 7 ; see Aquinas, Commentary, Bk. I, C h. 10, nos. 127-8 ). The commands or precepts, then, that lead to human happiness or flourishing is what Aquinas means by the natural law.

Aquinas distinguishes different levels of precepts or commands that constitute or comprise the natural law. The most universal is the command “Good is to be done and pursued and evil avoided ” ( ST I-II, 94, 2 ). This applies to everything and everyone, so much so that some consider it to be more of a description or definition of what we mean by “good.” For these philosophers, a thing is “good” just in case it is pursued or done by someone. Aquinas would agree with this to a certain extent; but he would say that that is a definition of an  apparent  good. Thus, this position of Aquinas has a certain phenomenological appeal: a person does anything and everything he or she does only because that thing at least “appears” to be good. Even when I choose something that I know is bad for myself, I nevertheless chooses it under some aspect of good, i.e., as some kind of good. I know the cake is fattening, for example, and I don’t choose to eat it  as  fattening. I do, however, choose to eat it as tasty (which is an apparent, though not a true, good). A true good is an object of desire which reason determines to be appropriate or fitting to a given person, in certain circumstances, in light of their universal human nature ( ST I-II, 94, 3 , esp. ad 3). Sometimes this will include eating cake, but not too much of it.

Precepts of the Natural Law

The precepts of the natural law are commands derived from the inclinations or desires natural to human beings; for Aquinas there is no problem in deriving “ought” from “is.” Since the object of every desire has the character or formality of “good,” there are a variety of goods we naturally seek. They are all subsumed under the First Principle of Practical Reasoning: The good is to be done and pursued, and evil avoided. This first principle is operative in all the precepts that comprise the natural law. Subsequent precepts of the natural law derive first from various sorts of inclinations as humans share these with other sorts of natural things, and second, as one discovers these goods in greater specificity ( ST I-II, 94, 2 ).

On the level that we share with all substances, the natural law commands that we preserve ourselves in being. Therefore, one of the most basic precepts of the natural law is to not commit suicide. (Nevertheless, suicide can, sadly, be chosen as an apparent good, e.g., as the cessation of pain; often it is not chosen at all, but the result of mental illness.) On the level we share with all living things, the natural law commands that we take care of our life, and transmit that life to the next generation. Thus, almost as basic as the preservation of our lives, the natural law commands us to rear and care for offspring. On the level that is most specific to humans, the fulfillment of the natural law consists in the exercise those activities that are unique and proper to humans, i.e., knowledge and love , and in a state that is also natural to human persons, i.e., society. The natural law, thus, commands us to develop our rational and moral capacities by growing in the virtues of intellect (prudence, art, and science ) and will ( justice , courage, temperance) ( ST I-II, 94, 3 ). Natural law also commands those things that make for the harmonious functioning of society (“Thou shalt not kill,” “Thou shalt not steal”). Human nature also shows that each of us have a destiny beyond this world, too. Man’s infinite capacity to know and love shows that he is destined to know and love an infinite being, God, and so, natural law commands the practice of religion.

All of these levels of precepts so far outlined are only the most basic. “The good is to be done and pursued and evil is to be avoided” is not very helpful for making actual choices. Therefore, Aquinas believes that one needs one’s reason to be perfected by the virtues , especially prudence, in order to discover precepts of the natural law that are more proximate to the choices that one has to make on a day-to-day basis. As is indicated in the table above, particular precepts, as they derive from more general ones in issuing forth in action, can conflict with each other. The command to save David might conflict with the apparent injunction that one ought not to lie to soldiers bent on unjustly executing him, but might cohere with the injunction not to give them information they have no just right to. Applying the natural law to cases, then, is more open to error, even though the general principles are true and apparent, and there is, in fact, a true and most rational application to certain particular circumstances ( ST I-II, 94, 3 ).

Application of the Natural Law as an Absolute / Objective Standard

Given that the natural law depends on the inclinations inherent in human nature (as ordained by the intelligent, loving providence of God, i.e., the Eternal Law) it applies to all people, at all times. Yet Aquinas readily acknowledges that the laws and morals of people can vary wildly. Rather than succumbing to moral relativism (where what is morally good and right is merely what each society or person thinks is such), Aquinas seeks both to uphold the objective and universal basis of morality in the natural law, and to explain the variety of moral and legal injunctions. Despite his belief that the natural law applies universally, Aquinas explains how this variety arises, first from the perspective of the generality of the precepts, and then from the perspective of the knowledge an individual has of the precepts.

From the perspective of the generality of the precepts, Aquinas reasons that the more general a precept is, the less is it open to exceptions. The general principles of both speculative reasoning (e.g., mathematics and the sciences) and practical reasoning (arts, ethics and politics) are necessary, and so the primary precepts of the natural law apply in all cases. The good is always to be done; life is always to be preserved. Yet, as one seeks to apply the general principles to particular cases, the particular circumstances necessitate greater variety in the kinds of actions required by the principle. Preserving life in the community may require the execution of murderers .

Although there is necessity in the general principles, the more we descend to matters of detail, the more frequently we encounter defects. … In matters of action, truth or practical rectitude is not the same for all, as to matters of detail, but only as to the general principles: and where there is the same rectitude in matters of detail, it is not equally known to all . ( ST I-II, 94, 4 )

From the perspective of the knowledge an of individual, the variety of ways of applying the natural law also leads to variability in knowing how to so apply the principles. The more general a precept is, the more likely it is to be known by a greater number of people. The more particular a precept of the natural law (or the application of a general precept to a particular case) is, the more likely it is that a particular individual will get it wrong.

Aquinas thus concludes that the greater the detail, the more likely it will be that people disagree about what the natural law requires:

Consequently, we must say that the natural law, as to general principles, is the same for all, both as to rectitude and as to knowledge. But as to certain matters of detail, which are conclusions, as it were, of those general principles, it is the same for all in the majority of cases, both as to rectitude and as to knowledge; and yet in some few cases it may fail, both as to rectitude, by reason of certain obstacles (just as natures subject to generation and corruption fail in some few cases on account of some obstacle), and as to knowledge, since in some the reason is perverted by passion, or evil habit, or an evil disposition of nature. ( ST I-II, 94, 4 )

Even though it is true that as one makes more particular applications of the general precepts of the natural law, the form that application takes is likely to be displayed in a greater variety of actions, nevertheless, the same natural law is being applied in each case, and the same natural law commands a variety of actions as given situations demand. What is the right thing to do might vary according to a variety of circumstances, yet in each case, the right thing to do is objective and necessary, a rational deduction of the certain general principles of moral action.

Just and Unjust Laws

Aquinas thus argues that the natural law cannot be changed, except by way of addition. Such additions, he says, are “things for the benefit of human life [which] have been added over and above the natural law, both by Divine law and by human laws ” ( ST I-II, 94, 5 ). Nothing can be subtracted from the natural law with regard to the primary precepts, and thus, no human law which commands something contrary to the natural law can be just. Interestingly, he notes, that certain features of society, while not being provided to humans by nature, accord with the natural law under the general principle of being “devised by human reason for the benefit of human life” ( ad 3 ). He includes among such non-natural features as consonant with natural law: clothing, private property and slavery. Yet by introducing the condition that just additions to the natural law must be for the benefit of human life, he allows, as we’ll see below, that should they fail this condition, they would thereby be subtractions from the natural law and so, unjust.

Given the universality and objective character of the natural law, Aquinas unsurprisingly asserts that it cannot be forgotten or “abolished from the human heart” ( ST I-II, 94, 6 ). Nevertheless, he recognizes that many people act as though they do not recognize this universal and objective standard of morality since they are inhibited by the influence of concupiscence or other passions , by an error of reasoning , or “by vicious customs and corrupt habits.” Indeed, as the third objection notes, there are whole societies which operate according to laws at variance with the natural law, declaring their departures as “just.” Aquinas responds that such laws abolish only the “secondary precepts of the natural law, against which some legislators have framed certain enactments which are unjust.” ( ST 94, 6 ad 3 ). This nuanced understanding of the natural law, then, provides a standard for judging just and unjust laws. He makes this criterion of just laws explicit when he turns to the origin of human law.

Consequently, every human law has just so much of the nature of law, as it is derived from the law of nature. But if in any point it deflects from the law of nature, it is no longer a law but a perversion of law.” ( ST I-II, 95, 2 )

Aquinas, thus, seems to grant that whatever judges a system of human laws must stand outside and above that system. The laws of Nazi Germany which prescribed the execution of Jews and dissidents and forbade their protection constituted “crimes against humanity,” not because these laws were in violation of other laws of Germany, or the laws of France or the United States. The reason that the attempted destruction of the Jews was wrong was not even because the whole rest of the world thought it was wrong. The crimes of Nazi Germany could be judged as crimes because they were violations of a law that stands apart from and above the laws of every nation; they were violations of the natural law. Natural law, then, serves as the standard against which we determine whether human positive laws are just or not.

One can see these principles at work in “ Letter from Birmingham City Jail ” by Dr. Martin Luther King, Jr. As King says:

I would be the first to advocate obeying just laws. One has not only a legal but a moral responsibility to obey just laws. Conversely, one has a moral responsibility to disobey unjust laws. I would agree with St. Augustine that “an unjust law is no law at all.” Now, what is the difference between the two? How does one determine whether a law is just or unjust? A just law is a man made code that squares with the moral law or the law of God. An unjust law is a code that is out of harmony with the moral law. To put it in the terms of St. Thomas Aquinas: An unjust law is a human law that is not rooted in eternal law and natural law. Any law that uplifts human personality is just. Any law that degrades human personality is unjust. All segregation statutes are unjust because segregation distorts the soul and damages the personality. It gives the segregator a false sense of superiority and the segregated a false sense of inferiority.

The justification to which King appeals in order to show that segregation laws are unjust is not other laws of Alabama or of the United States, but the natural law as it is founded in human nature. Human nature demands a true sense of equality and dignity, and because segregation laws violate that equality and dignity, they are unjust. Segregation laws clearly diminished the dignity, and thus damage the personality of blacks in Alabama. Interestingly, King asserts that segregation laws were harmful to the white majority, distorting their proper dignity and damaging their personality as well. In both cases, segregation laws are an affront to human dignity, founded as it is in our common human nature.

The Thomistic notion of natural law has its roots, then, in a quite basic understanding of the universe as caused and cared for by God, and the basic notion of what a law is. It is a fairly sophisticated notion by which to ground the legitimacy of human law in something more universal than the mere agreement and decree of legislators. Yet, it allows that what the natural law commands or allows is not perfectly obvious when one gets to the proximate level of commanding or forbidding specific acts. It grounds the notion that there are some things that are wrong, always and everywhere, i.e., “crimes against humanity,” while avoiding the obvious difficulties of claiming that this is determined by any sort of human consensus. Nevertheless, it still sees the interplay of people in social and rational discourse as necessary to determine what in particular the natural law requires.

Updated February 24, 2024

Revised and expanded August 26, 2021

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Natural Law as a Threat to Justice

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Jeremy Bentham and The Foundation of Utilitarianism

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Natural law is a moral and ethical doctrine that posits that certain ethical principles are inherent in nature and independent of human actions or institutions. It is based on the belief that there are certain ethical and moral norms that can be discovered through reason or revelation, rather than just the laws that are decided by politicians or legal systems. Natural law theory emphasizes that human laws need to be consistent with, and derived from, these natural laws. It has been deeply influential in the development of Western thought and is still relevant in contemporary political and legal debates.

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Natural law ethics

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During most of the 20th century, most secular moral philosophers considered natural law ethics to be a lifeless medieval relic, preserved only in Roman Catholic schools of moral theology . In the late 20th century the chief proponents of natural law ethics continued to be Roman Catholic, but they began to defend their position with arguments that made no explicit appeal to religious beliefs. Instead, they started from the claim that there are certain basic human goods that should not be acted against in any circumstances. The list of goods offered by John Finnis in the aforementioned Natural Law and Natural Rights , for example, included life, knowledge, play, aesthetic experience, friendship, practical reasonableness, and religion. The identification of these goods is a matter of reflection, assisted by the findings of anthropologists. Furthermore, each of the basic goods is regarded as equally fundamental; there is no hierarchy among them.

It would, of course, be possible to hold a consequentialist ethics that identified several basic human goods of equal importance and judged actions by their tendency to produce or maintain these goods. Thus, if life is a good, any action that led to a preventable loss of life would, other things being equal, be wrong. Proponents of natural law ethics, however, rejected this consequentialist approach; they insisted that it is impossible to measure the basic goods against each other. Instead of relying on consequentialist calculations, therefore, natural law ethics assumed an absolute prohibition of any action that aims directly against any basic good. The killing of the innocent, for instance, is always wrong, even in a situation where, somehow, killing one innocent person is the only way to save thousands of innocent people. What is not adequately explained in this rejection of consequentialism is why the life of one innocent person cannot be measured against the lives of a thousand innocent people—assuming that nothing is known about any of the people involved except that they are innocent.

Natural law ethics recognizes a special set of circumstances in which the effect of its absolute prohibitions would be mitigated . This is the situation in which the so-called doctrine of double effect would apply. If a pregnant woman, for example, is found to have a cancerous uterus, the doctrine of double effect allows a doctor to remove it, notwithstanding the fact that such action would kill the fetus. This allowance is made not because the life of the woman is regarded as more valuable than the life of the fetus, but because in removing the uterus the doctor is held not to aim directly at the death of the fetus; instead, its death is an unwanted and indirect side effect of the laudable act of removing a diseased organ. In cases where the only way of saving the woman’s life is by directly killing the fetus, the doctrine provides a different answer. Before the development of modern obstetric techniques, for example, the only way of saving a woman whose fetus became lodged during delivery was to crush the fetus’s skull. Such a procedure was prohibited by the doctrine of double effect, for in performing it the doctor would be directly killing the fetus. This position was maintained even in cases where the death of the mother would certainly also bring about the death of the fetus. In these cases, the claim was made that the doctor who killed the fetus directly would be guilty of murder, but the deaths from natural causes of the mother and the fetus would not be his doing. The example is significant, because it indicates the lengths to which proponents of natural law ethics were prepared to go in order to preserve the absolute nature of their prohibitions.

In the last two decades of the 20th century, there was a revival of interest in the Aristotelian idea that ethics should be based on a theory of the virtues rather than on a theory of what one ought to do. This revival was influenced by Elizabeth Anscombe and stimulated by Philippa Foot, who in essays republished in Virtues and Vices (1978) explored how acting ethically could be in the interest of the virtuous person. The Scottish philosopher Alasdair MacIntyre , in his pessimistic work After Virtue (1980), lent further support to virtue ethics by suggesting that what he called “the Enlightenment Project” of giving a rational justification of morality had failed. In his view, the only way out of the resulting moral confusion was to ground morality in a tradition, such as the tradition represented by Aristotle and Aquinas .

Virtue ethics, in the view of its proponents, promised a reconciliation of morality and self-interest. If, for example, generosity is a virtue, then a virtuous person will desire to be generous; and the same will hold for the other virtues. If acting morally is acting as a virtuous human being would act, then virtuous human beings will act morally because that is what they are like, and that is what they want to do. But this point again raised the question of what human nature is really like. If virtue ethicists hope to develop an objective theory of the virtues, one that is valid for all human beings, then they are forced to argue that the virtues are based on a common human nature; but, as was noted above in the discussion of naturalism in ethics, it is doubtful that human nature can serve as a standard of what one would want to call morally correct or desirable behaviour. If, on the other hand, virtue ethicists wish to base the virtues on a particular ethical tradition, then they are implicitly accepting a form of ethical relativism that would make it impossible to carry on ethical conversations with other traditions or with those who do not accept any tradition at all.

A rather different objection to virtue ethics is that it relies on an idea of the importance of moral character that is unsupported by the available empirical evidence . There is now a large body of psychological research on what leads people to act morally, and it points to the surprising conclusion that often very trivial circumstances have a decisive impact. Whether a person helps a stranger in obvious need, for example, largely depends on whether he is in a hurry and whether he has just found a small piece of change. If character plays less of a role in determining moral behaviour than is commonly supposed, an ethics that emphasizes virtuous character to the exclusion of all else will be on shaky ground.

In work published from the 1980s, feminist philosophers argued that the prevalent topics, interests, and modes of argument in moral philosophy reflect a distinctively male point of view, and they sought to change the practice of the discipline to make it less male-biased in these respects. Their challenge raised questions in metaethics , normative ethics , and applied ethics . The feminist approach received considerable impetus from the publication of In a Different Voice (1982), by the American psychologist Carol Gilligan . Gilligan’s work was written in response to research by Lawrence Kohlberg , who claimed to have discovered a universal set of stages of moral development through which normal human beings pass as they mature into adulthood. Kohlberg claimed that children and young adults gradually progress toward more abstract and more impartial forms of ethical reasoning, culminating in the recognition of individual rights. As Gilligan pointed out, however, Kohlberg’s study did not include females. When Gilligan studied moral development in girls and young women, she found less emphasis on impartiality and rights and more on love and compassion for the individuals with whom her subjects had relationships. Although Gilligan’s findings and methodology were criticized, her suggestion that the moral outlook of women is different from that of men led to proposals for a distinctly feminist ethics—an “ethics of care.” As developed in works such as Caring (1984), by the American feminist philosopher Nel Noddings , this approach held that normative ethics should be based on the idea of caring for those with whom one has a relationship, whether that of parent, child, sibling, lover, spouse, or friend. Caring should take precedence over individual rights and moral rules, and obligations to strangers may be limited or nonexistent. The approach emphasized the particular situation, not abstract moral principles.

Not all feminist moral philosophers accepted this approach. Some regarded the very idea that the moral perspective of women is more emotional and less abstract than that of men as tantamount to accepting patriarchal stereotypes of women’s thinking. Others pointed out that, even if there are “feminine” values that women are more likely to hold than men, these values would not necessarily be “feminist” in the sense of advancing the interests of women. Despite these difficulties, feminist approaches led to new ways of thinking in several areas of applied ethics, especially those concerned with professional fields like education and nursing, as well as in areas that male philosophers in applied ethics had tended to neglect, such as the family .

All of the normative theories considered so far have had a universal focus—i.e., the goods they seek to achieve, the character traits they seek to develop, or the principles they seek to apply pertain equally to everyone. Ethical egoism departs from this consensus , because it asserts that moral decision making should be guided entirely by self-interest. One great advantage of such a position is that it avoids any possible conflict between self-interest and morality. Another is that it makes moral behaviour by definition rational (on the plausible assumption that it is rational to pursue one’s own interests).

Two forms of egoism may be distinguished. The position of the individual egoist may be expressed as: “Everyone should do what is in my interests.” This is indeed egoism, but it is incapable of being universalized (because it makes essential reference to a particular individual); thus, it is arguably not an ethical principle at all. Nor, from a practical perspective, is the individual egoist likely to be able to persuade others to follow a course of action that is so obviously designed to benefit only the person who is advocating it.

Universal egoism is expressed in this principle: “Everyone should do what is in his own interests.” Unlike the principle of individual egoism, this principle is universalizable. Moreover, many self-interested people may be disposed to accept it, because it appears to justify acting on desires that conventional morality might prevent one from satisfying. Universal egoism is occasionally seized upon by popular writers, including amateur historians, sociologists, and philosophers, who proclaim that it is the obvious answer to all of society’s ills; their views are usually accepted by a large segment of the general public. The American writer Ayn Rand is perhaps the best 20th-century example of this type of author. Her version of egoism, as expounded in the novel Atlas Shrugged (1957) and in The Virtue of Selfishness (1965), a collection of essays, was a rather confusing mixture of appeals to self-interest and suggestions of the great benefits to society that would result from unfettered self-interested behaviour. Underlying this account was the tacit assumption that genuine self-interest cannot be served by lying, stealing, cheating, or other similarly antisocial conduct.

As this example illustrates, what starts out as a defense of universal ethical egoism very often turns into an indirect defense of consequentialism: the claim is that everyone will be better off if each person does what is in his own interest. The ethical egoist is virtually compelled to make this claim, because otherwise there is a paradox in the fact that he advocates ethical egoism at all. Such advocacy would be contrary to the very principle of ethical egoism, unless the egoist stands to benefit from others’ becoming ethical egoists. If his interests are such that they would be threatened by others’ pursuing their own interests, then he would do better to advocate altruism and to keep his belief in egoism a secret.

Unfortunately for ethical egoism, the claim that everyone will be better off if each person does what is in his own interests is incorrect. This is shown by thought experiments known as “ prisoner’s dilemmas ,” which played an increasingly important role in discussions of ethical theory in the late 20th century ( see game theory ). The basic prisoner’s dilemma is an imaginary situation in which two prisoners are accused of a crime . If one confesses and the other does not, the prisoner who confesses will be released immediately and the prisoner who does not will be jailed for 20 years. If neither confesses, each will be held for a few months and then released. And if both confess, each will be jailed for 15 years. It is further stipulated that the prisoners cannot communicate with each other. If each of them decides what to do purely on the basis of self-interest, he will realize that it is better for him to confess than not to confess, no matter what the other prisoner does. Paradoxically, when each prisoner acts selfishly—i.e., as an egoist—the result is that both are worse off than they would have been if each had acted cooperatively.

Although the example might seem bizarre, analogous situations occur quite frequently on a larger scale. Consider the dilemma of the commuter. Suppose that each commuter finds his private car a little more convenient than the bus, but when each commuter drives a car, the traffic becomes extremely congested. So everyone is better off in the situation where everyone takes the bus than in the situation where everyone drives a car. Because private cars are somewhat more convenient than buses, however, and because the overall volume of traffic is not appreciably affected by one more car on the road, it is in the interests of each commuter to continue driving. At least on the collective level, therefore, egoism is self-defeating—a conclusion well brought out by the English philosopher Derek Parfit in Reasons and Persons (1984).

The fact that ethical egoism is collectively self-defeating does not mean that it is wrong. An ethical egoist might still maintain that it is right for each person to pursue his own interests, even if this would bring about worse consequences for everyone. His position would not be self-contradictory, though it would be “self-effacing,” since it would require him to avoid promoting egoism in public and to keep his true ethical beliefs a secret.

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Natural Law Essay Examples

Impact of natural law on canadian law.

The ideas of natural law were originated by Aristotle who argues that everything in life has a purpose and goal. Aristotle’s ideas of natural law were developed by St. Thomas Aquinas in the 13th century. Natural laws start with basic principles, people can be aware...

Jurisprudence: Types of Law Schools

The word “Jurisprudence” refers to law’s philosophy or science. Many experts of this subject have their own diverse styles of stating the law. There are a few schools of jurisprudence that have their own base for decision-making. The contemporary way of thinking of law, which...

Natural Law Vs Positive Law

Since the Greek era, there has been a distinction between positive law and natural and that brought along several supporters of each theory. The distinction lies in the fact that positive laws are human-made laws that oblige or specify a certain action, while natural laws...

St. Thomas Aquinas’ Natural Law Theory

Despite being one of the most esteemed philosophical theologians that we have seen thus far, St. Thomas Aquinas's Natural Law Theory has some empty room for arguing his beliefs, in contrast to my personal beliefs. This paper will look at the various reasons why St....

Understanding Quine’s Naturalism Philosophy Via Epistemological Holism

The goal of this paper is to better understand Quine’s philosophy of science by explicating his naturalism and interaction with other academics. By tackling the indispensability argument from multiple angles, I build off Penelope Maddy’s theory about epistemological holism and speculate how a Quinean might...

Whether the School of Natural Law and Positivism Are Anachronistic for the Legal Environment of Zambia

Jurisprudence is a field of study which concerns itself with the nature of law and an attempt to answer the question, what is law? remains a matter of legal scholarship that elicits answers that garner no consensus amongst students, academicians, and legal practitioners, among others....

Why Divine Command Theory is Superior to Cultural Relativism and the Natural Law Tradition

Moral traditions and objections are the foundation that people place their principles on and are common throughout philosophy. This essay will consider normative cultural relativism, the natural law tradition, divine command theory, and determinism and nihilism. This essay will show why divine command theory is...

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