Natural Law Theory

Natural Law Theory

Main source: Finnis, John, “Natural Law Theories”, The Stanford Encyclopedia of Philosophy (Fall 2011 Edition), Edward N. Zalta (ed.), URL = .

Definition of Legal Law

Among the theories that define legal law there are:

  • the theory of Hans Kelsen, who argues that law is completely separate from morality, and
  • the theory of John Finnis, who argues that law is completely tied up in morality.

I think the two theories aren’t actually that hard to reconcile to form a big Finnis-Kelsen theory.


Kelsen’s theory creates a discipline legal science, which deals only with questions of law. Kelsen acknowledges that a judge/legislator/whoever will make decisions that deal with non-legal factors, but he excludes such factors from legal science. While Kelsen himself argues that there are no objective morals, his theory would still work if such morals did exist because the Pure Theory of Law exists only within legal science, and morals exist outside of legal science.

Meanwhile, Finnis proposes objective, basic goods that every human wants to participate in. The best way to do this is to coordinate as a society, and a very good way to coordinate is through law. However, Finnis grants that any decision that there are many equally valid moral decisions – any decision made in accordance with the seven basic goods and the nine requirements of practical reason is a morally acceptable decision. Therefore there are many ways to construct a legal system.

Additionally, Finnis distinguishes between legal validity (which is within legal science) and moral validity (beyond legal science). You can implement a legal system that does not fulfil the basic goods, and such a system will have legal validity, but not moral validity.

It seems to me that these theories are not actually opposing. Instead they slide by each other, dealing with different subject matter, and so we can put them together.
Finnis’s theory tells us how the law should be, while Kelsen’s tells us how it actually is. We can examine a particular law and asks questions of legal science, such as ‘is this law legally valid?’ or we can ask moral questions like ‘is this law morally valid?’ Since legal science is separate from morality, the two theories will not contradict, and any legal question that we ask will be answered by exactly one theory.

We can look at a society, and we can differentiate between that society’s underlying moral rules and its positively created legal rules. We can examine the first system using Finnis, and the second system using Kelsen. This allows us to answer questions like “How good is this legal system?” because we have precise definitions of (1) the legal system and (2) what it means to be good.

The one area of overlap is decision making – what factors will a judge (or some other legal organ) take into account when they make a legal decision? Such a decision takes into account both moral and legal considerations. However, both theories are incomplete in describing this legal process – Kelsen says that it is beyond legal science, while Finnis says that as long as you obey practical reason, you can do whatever you want. Neither theory explains or prescribes the thinking process of such a legal organ, so there is no contradiction here. You could admit however, that the Finnis-Kelsen theory is therefore not a comprehensive theory of law, and if that was what you wanted, you’d need to add even more stuff to it.

Pure Theory of Law

In the Pure Theory of Law, Kelsen argues that natural law is both wrong and incoherent, and so he would probably not be happy with a Finnis-Kelsen theory. However, as I have said, the Pure Theory does not fail if we allow the existence of natural law.

Kelsen’s specific arguments against natural law are not very effective against Finnis’s theory:

Kelsen first argues that natural law must be wrong, because there are no objective moral standards. He says that this is clear because no common morals can be found between societies. Finnis’s theory of basic goods expressly deals with this argument; his reply can be summarised as ‘Yeah, but people who don’t believe in the basic goods are wrong.’ More details can be found in my summary posts on Finnis.

Kelsen also argues that natural law is incoherent – any system of law is founded on a Grundnorm, which is arbitrarily chosen no matter what.
We can deal with this argument too. Firstly, natural law is distinctly different to positive law, and exists outside of legal science. Therefore it does not require a Grundnorm. However, natural law does need ‘moral validity,’ and the source of this validity must come from some moral form of a Grundnorm. But the decision of which Grundnorm to adopt is not arbitrary – it must reflect the law that is actually followed. If we want to choose a moral Grundnorm that grants moral validity, it must reflect the morals that actually exist. Therefore the choice of moral Grundnorm is not arbitrary.

Therefore Kelsen’s arguments for moral relativism do not do well against Finnis’s theory, but this does not mean that the Pure Theory itself is weakened. Once Kelsen’s theory makes this concession, I think that it fits quite well with Finnis’ theory to create a Finnis-Kelsen theory that describes natural and positive law, and can discern relationships between the two.

Neat Parallel

The natural world is confusing and uncertain. We try to construct scientific theories that are logical and precise, which approximate the natural world. We have to make trade-offs between the logical completeness of the theory, and the theory’s ability to accurately describe nature. In the same way, the natural law is confusing and uncertain. We construct systems of positive law that are logical and precise, which approximate the natural law. We have to make trade-offs between the logical completeness of a legal system, and the legal system’s ability to accurately replicate the natural law. [1]

Natural Law Theories Explained

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 2005, 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.
1.2 Political authority as remedy for anarchy, injustice and impoverishment

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.

Rule of law as remedy for the dangers in having rulers

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 1980/2011, 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 but 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.
1.4 Ius gentium—ius cogens—mala in se—human rights: legal rules and rights posited because morally necessary parts of any legal system

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 [without agreement or enactment or other forms of adoption] in relation to 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).

“Purely positive law: determinationes and their legal-moral authority for citizens and judges (facts made reasons for action)

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.

“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. [2]

Natural Law Theory

Related Work and Conclusions


See Also

References (Papers)

  • Truth And Politics: A Symposium On Peter Simpson's Political Illiberalism: A Defense Of Freedom., Gerard V. Bradley, Jan 2017
  • Jurisprudence: Readings And Cases, Dr. Miriam Theresa Rooney, Dec 2016
  • The Legal Philosophy Of Roscoe Pound, Linus J. Mcmanaman, O.S.B., Dec 2016
  • Natural Law In The Church Today, George M. Regan, C.M., Dec 2016
  • Natural Law Actualities, Miriam T. Rooney, Nov 2016
  • The Need For Renewal In Natural Law, George M. Regan, C.M., Nov 2016
  • The Case Of Natural Obligations, David V. Snyder, Nov 2016
  • On The Incoherence Of Legal Positivism, John M. Finnis, Oct 2016
  • Virtue And The Constitution Of The United States, John M. Finnis, Oct 2016
  • Public Reason, Abortion, And Cloning, John M. Finnis, Oct 2016
  • Subsidiarity's Roots And History: Some Observations, John M. Finnis, Oct 2016
  • Grounding Human Rights In Natural Law, John M. Finnis, Oct 2016
  • Coexisting Normative Orders? Yes, But No, John M. Finnis, Oct 2016
  • On “The Critical Legal Studies Movement”, John M. Finnis, Oct 2016
  • Equality And Differences, John M. Finnis, Oct 2016
  • Morality In Legal Practice, Rev. William F. Cahill, Oct 2016
  • Civil Disobedience And Natural Law, Mark R. Macguigan, Oct 2016
  • The Natural Law Philosophy Of Lon L. Fuller, Charles L. Palms, C.S.P., Oct 2016
  • The Basis Of The Natural Law In Locke's Philosophy, James W. Byrne, Oct 2016
  • Pacem In Terris – Human Rights And Duties In Natural Law, Pope John Xxiii, Oct 2016
  • Natural Law Norms, Brendan F. Brown, Sep 2016
  • Natural And Moral Obligations, Pedro F. Entenza-Escobar, Sep 2016
  • Kain V. Department Of Environmental Protection, Sarah M. Danno, Aug 2016



  1. By Hugh McCarthy
  2. Main source: Finnis, John, “Natural Law Theories”, The Stanford Encyclopedia of Philosophy (Fall 2011 Edition), Edward N. Zalta (ed.)

See Also

  • Legal Positivism
  • Natural Law Theory
  • Interpretivist Theories of Law
  • Legal Realism
  • Nature of Law

Further Reading

  • C. Fred Alford (2010). Narrative, Nature, and the Natural Law: From Aquinas to International Human Rights. Palgrave Macmillan.
  • Robert C. Baker (2011). Natural Law, Human Sexuality, and Forde’s “Acid Test”. In Robert C.
  • Baker & Roland Cap Ehlke (eds.), Natural Law: A Lutheran Reappraisal. Concordia Pub. House
  • Finnis, J. (2011, first published 1980). Natural law and natural rights. Oxford: Oxford University Press
  • Robert C. Baker & Roland Cap Ehlke (eds.) (2011). Natural Law: A Lutheran Reappraisal. Concordia Pub. House.
  • Gail Belaief (1971). Spinoza’s Philosophy of Law. The Hague,Mouton.
  • Stephen Buckle (1991). Natural Law and the Theory of Property: Grotius to Hume. Oxford University Press.




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