Natural Law is the doctrine that moral truths are accessible to reason — grounded in human nature itself — distinct from divine command, distinct from positive law, but ultimately consistent with both.
natural-law
The doctrine that there is a moral law accessible to human reason, grounded in human nature and the rational structure of reality, distinct from but related to divine command and positive law.
The problem it answers
Is morality merely conventional — a set of arrangements that differ from culture to culture and rest on no deeper foundation than the agreement of those who happen to share them? Or is there a moral order that is genuinely natural, accessible to human reason regardless of convention, and binding on humans as humans rather than as members of any particular culture or community?
The Western philosophical tradition has, for over two thousand years, affirmed the second answer under the heading of natural law. There is a moral order grounded in human nature itself; this order is accessible to human reason; it is the foundation against which positive laws (the actual laws of actual societies) are evaluated; it is distinct from divine command (though ultimately consistent with it on theist accounts).
The core claim
The core claim of natural law theory has three parts.
There is a moral order grounded in nature. Moral truths are not merely conventional or culturally constructed; they have a foundation in the way things are, particularly in the structure of human nature.
This order is accessible to reason. Humans, by the exercise of reason, can come to know what natural law requires. The knowledge is not always easy or complete, but it is in principle available without special revelation.
Natural law is the standard for evaluating positive law. Human-made laws are legitimate to the extent that they conform to natural law; an unjust positive law (one that contradicts natural law) is, on the strong version of the doctrine, not properly law at all.
History in one paragraph
The doctrine has roots in Plato and Aristotle but takes its developed form in the Stoic tradition. Chrysippus and the Roman Stoics (Cicero especially in De Re Publica and De Legibus) developed the doctrine that there is a single natural law accessible to all rational beings, grounded in the rational structure of the cosmos (logos). The Roman legal tradition (Ulpian, Gaius) absorbed and codified the Stoic categories; the famous Ulpianic definition of jus naturale shaped Western legal thought for centuries. The Christian tradition through Augustine and especially Aquinas integrated natural law with Christian theology. Aquinas's treatise on law in the Summa Theologiae (Ia-IIae qq.90–108) is the foundational Christian natural law treatment: eternal law is God's plan for creation; natural law is the rational creature's participation in eternal law, knowable by reason; human law is the specification of natural law in particular societies; divine law is the supplement given by revelation. The early modern natural law tradition (Grotius, Pufendorf, Locke) secularized substantial portions of the doctrine, developing accounts of natural rights and the social contract that grounded modern liberal political theory. The Enlightenment saw the doctrine narrowed and partly transformed (Kant's account of moral law is recognizably continuous though substantially revised). The nineteenth and twentieth centuries saw the doctrine challenged by legal positivism (John Austin, H.L.A. Hart) and by historicism (Hegel, the Marxist tradition). The mid-twentieth century saw a major revival: Lon Fuller's The Morality of Law (1964), John Finnis's Natural Law and Natural Rights (1980), and the broader work of the New Natural Law school (Germain Grisez, Robert P. George) returned natural law to active discussion in legal philosophy and political theory.
Aquinas's account
The Thomist account in Summa Theologiae Ia-IIae qq.90–108 is the most fully developed Christian natural law theory and the standard reference. The architecture has four kinds of law:
Eternal law. God's wise plan for the entire creation, the rational ordering of all things toward their proper ends. Eternal law is what God knows; it is identical with God's wisdom.
Natural law. The rational creature's participation in eternal law. Because humans are rational, they can grasp portions of the eternal law by the use of reason. Natural law is therefore what humans know of God's plan by natural reflection on human nature and the goods it directs us toward.
Human law. Particular laws enacted by particular human societies. Human law derives its authority from natural law (positive laws that contradict natural law are not properly law). But natural law underdetermines human law; many different specific arrangements are compatible with the natural law, and human authority must choose among them for the particular society.
Divine law. The supplement to natural law given by revelation. Divine law covers what reason cannot establish (specific commands about worship, for example) and corrects errors that natural reflection alone might fall into.
Within natural law itself, Aquinas distinguishes the first principle (the good is to be done and pursued, and the evil is to be avoided) from secondary precepts (the more specific moral norms derived from human goods). The first principle is self-evident; secondary precepts require reflection and may be more or less clearly seen depending on the moral training and cultural conditions of the agent.
The early modern transformation
The seventeenth-century natural law theorists — Hugo Grotius, Samuel Pufendorf, John Locke — transformed the doctrine in ways consequential for modern political theory. The most significant move was the secularization: Grotius famously argued that natural law would hold etiamsi daremus non esse Deum (even if we were to grant that God does not exist). The move opened the possibility of a natural law tradition independent of any particular theological commitment.
The associated development was the language of natural rights. Where the medieval natural law tradition had focused on objective duties (the moral obligations grounded in human nature), the early modern tradition increasingly focused on subjective rights (the entitlements individuals have by virtue of their nature). Locke's Second Treatise of Government (1689) is the foundational text: humans have natural rights to life, liberty, and property; legitimate government exists to protect these rights; government that systematically violates them loses its legitimacy.
The American founding (the Declaration of Independence, the Bill of Rights) is recognizably in this tradition. The contemporary international human rights framework (the Universal Declaration of Human Rights, 1948) is its later descendant.
The positivist challenge
The nineteenth-century rise of legal positivism challenged natural law theory at its foundations. John Austin's The Province of Jurisprudence Determined (1832) defined law as the command of the sovereign; whether the command was just was a separate question from whether it was law. H.L.A. Hart's The Concept of Law (1961) provided the major twentieth-century development: law is a system of rules grounded in social practice; the question of whether the law is morally good is separable from the question of what the law is.
The Hart-Fuller debate (Hart's positivism versus Lon Fuller's natural law) in the late 1950s was one of the major events of twentieth-century legal philosophy. The Nazi laws of the 1930s and 1940s provided the test case: are those laws in the strict sense, or do they fail to count as law precisely because of their gross injustice? Hart held the former; Fuller the latter.
The contemporary debate remains active. John Finnis's Natural Law and Natural Rights (1980) developed a sophisticated natural law theory engaging directly with Hart; the dispute continues in current legal philosophy through writers including Robert P. George, Mark Murphy, and Jeremy Waldron.
Common confusions
Natural law is not the same as the laws of nature. The English natural law is ambiguous: it can name the moral doctrine or the descriptive regularities of physical nature. The two are distinct; the moral doctrine concerns normative truth, not physical regularity.
Natural law does not require theism. The early modern secularization (Grotius's etiamsi daremus) demonstrated that the doctrine can be developed without explicit theological commitment. Many contemporary natural law theorists (most prominently John Finnis) work within a framework that is intelligible to theists and non-theists alike.
Natural law is not the same as natural rights. The two are related but distinct. Natural law primarily concerns objective duties grounded in nature; natural rights primarily concern subjective entitlements. The rights tradition emerged out of the law tradition in the early modern period.
Live debates
The New Natural Law theory. Germain Grisez, John Finnis, and Robert P. George have developed a version of natural law theory that grounds moral norms in basic goods of human nature (life, knowledge, friendship, religion, work, etc.) rather than in the older Aristotelian teleological framework. The position has been influential in contemporary Catholic moral philosophy and in conservative legal thought.
Natural law and biology. Can evolutionary biology provide naturalist grounding for normative claims about human nature? The literature on evolutionary ethics, capabilities theory (Martha Nussbaum), and natural goodness (Philippa Foot) engages this question from various directions.
Natural law and international human rights. Are contemporary human rights properly grounded in natural law, or do they require some other foundation (international consensus, social construction)? The literature in international legal theory is substantial.
Contemporary engagement
Major recent scholarly work includes John Finnis's Natural Law and Natural Rights (1980; 2nd ed. 2011) and his Aquinas: Moral, Political, and Legal Theory (1998), Mark Murphy's Natural Law in Jurisprudence and Politics (2006), Russell Hittinger's The First Grace (2003), and the essays collected in Natural Law and Modern Moral Philosophy (Paul, Miller, Paul, eds., 2001). The major journals include the American Journal of Jurisprudence, Law and Philosophy, and Oxford Journal of Legal Studies. The Stanford Encyclopedia of Philosophy entries on natural law theory in ethics and in legal theory are standard reference points.
Further reading
- Aquinas — the great medieval natural law theorist
- Stoicism — the tradition where the doctrine takes developed form
- Scholasticism — the medieval framework
- Justice — the closely related normative concept
- Logos — the cosmic rational order natural law participates in
- Summa Theologiae — the foundational Christian text
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