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Natural Law (IusNaturalism)

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This article is part of the Basic Course on Libertarianism and the Austrian School of Economics-> Module 2: Libertarianism and its ethical foundations

Last updated: 2026-01-13

Definition

Natural Law (IusNaturalism) (also called Natural Law or Natural Right) is one of the oldest and most persistent currents in the philosophy of law, ethics, and politics. It affirms that there exist principles of justice, rights, or ethical norms that are universal, immutable, and superior to human laws (positive law), derived from human nature, reason, or an eternal divine law.

For a natural-law thinker, the validity of a law does not depend on a King, Emperor, Dictator, Sacred Book, or Parliament having approved it, but on its being just and respecting human nature.

This idea is what historically allowed absolute power to be challenged: if the King issues a law that goes against human nature, that law is invalid.

The 4 Fundamental Principles of Natural Law

1. Universality

The principles of natural law apply to all human beings equally, regardless of nationality, era, social class, culture, or religion. They are rights held simply by virtue of being born human.

2. Immutability

Unlike human laws (positive law), which change according to the government of the day, natural law does not change with time. What was just by nature a thousand years ago (such as the right to life) still is today.

3. Superiority

Natural law stands at the top of the hierarchy. If a law issued by the State (positive law) contradicts a natural principle, the citizen has no moral obligation to obey it. This is where the concept of “unjust law” arises.

4. Cognizability (Reason)

These principles are not a mystery; they can be discovered by any person through the use of reason. One does not need a divine revelation or a law degree to understand that killing or enslaving another human being is wrong by nature.

Branches of Natural Law

Natural Law has 2 branches, more or less defined:

  • A Christian theological branch, with Thomas Aquinas, which sees natural law as originating in God.
  • A more rational and secular branch:
    • John Locke: who defends a rational and empirical approach. Locke was a Protestant Christian and his believing approach shows in his ideas.
    • Grotius and Pufendorf: who defend a rational approach even if God did not exist.

Natural Laws for the human being

Natural law is not a written code, but a set of principles derived from reason and observation of human nature. There is no “written” list of what the natural rights are. The 2 branches we named earlier (theological and rational) reach almost the same conclusion, with minimal differences. From the rational point of view, if you ask yourself “What is good for the human being?”, you will arrive at a list similar to the one below:

  • Preservation of life (without life there is nothing)
  • Liberty (the human being is not made for slavery)
  • Private property (the fruit of your work and liberty)
  • Procreation and care of offspring
  • Search for knowledge and truth
  • Promotion of the common good
  • Justice and respect for contracts (in order to live in society)

To understand it better, it is useful to compare it with its philosophical “rival”:

Characteristic Natural Law (Natural Right) Legal Positivism (Positive Law)
Origin Human nature / Reason. The will of the State / The legislator.
Criterion of validity Justice (It must be ethical). Legality (It must follow the formal process).
Can it be changed? No, it is eternal. Yes, according to the needs of the moment.
Relation to morality Law and Ethics are united. Law and Ethics are separate things.

Different Natural Law ideas

There is no single homogeneous “school,” but several historical stages with different approaches: classical (ancient and medieval), modern (rationalist and secular), and contemporary (revived after the 20th century). The main authors vary by era, but these are the most influential and representative:

Theological and Classical Natural Law

  • Thomas Aquinas: Defines natural law as the participation of the rational creature in the eternal law (God’s reason). He holds that man can recognize the injustice of a norm and, although he must obey for the common good, positive law is only valid if it is just and in conformity with natural reason.
  • Francisco de Vitoria: Considers that natural law is a “right reason” in conformity with human nature created by God. He was a pioneer in applying this to the international realm, defending that all men (including the American indigenous peoples) possess natural rights such as liberty, property, and sovereignty by the simple fact of being human.

Rationalist and Contractualist Natural Law

  • Hugo Grotius: He is considered the father of modern natural law. He proposed that natural law would exist even if God did not exist, grounding it exclusively in reason and in the sociable nature of the human being.
  • Thomas Hobbes: Subverts the traditional idea by grounding natural right in the instinct of self-preservation. For him, in the “state of nature” man has a right to everything, but life is “poor, nasty, and short,” so individuals cede their rights to the sovereign (Leviathan) in exchange for security.
  • Samuel von Pufendorf: Defines natural law as a set of universal principles known by reason (such as non-aggression and reparation of damages) that govern before the creation of the State. He introduces the idea that man possesses a connatural dignity and the duty to assist others.
  • John Locke: Holds that men possess inalienable natural rights (life, liberty, and property) prior to the State. Government is created through a social contract with the sole end of protecting those rights; if the sovereign violates them, the people have the right of resistance.

Enlightenment and Political Evolution

  • Jean-Jacques Rousseau: Argues that in the State of nature man is free and good (“the noble savage”), but society and private property corrupt him. The social contract seeks to recover a form of civil liberty through the “general will,” where the individual gives themselves over to the community to be “forced to be free” under laws they have given themselves.
  • Voltaire: Defends natural right from a humanist and social-reform perspective. For him, natural right translates into freedom of thought, religious toleration, and equality before the law, opposing fiercely torture and the abuses of the judicial system of his time.

Other notables of this era:

Christian Wolff, Gottfried Leibniz (rational influences), Montesquieu (separation of powers influenced by natural ideas).

Contemporary natural law (20th–21st century)

Revived after the horror of totalitarianism (Nazism, Stalinism) and legal positivism (which separated law and morality).

  • Jacques Maritain — Thomist Catholic; influenced the Universal Declaration of Human Rights (1948).
  • John Finnis — Main exponent of the “new natural law” (New Natural Law Theory), in Natural Law and Natural Rights (1980): rights based on basic human goods accessible by practical reason.
  • Lon Fuller — In The Morality of Law (1964) defends an “internal morality” of law (principles of legality) that connects with natural law.
  • Heinrich Rommen, Leo Strauss, Russell Hittinger — Revive Thomism and the critique of positivism.

Critiques of Natural Law

  • Vagueness and indefiniteness of the principles: The principles of natural law (such as "do good and avoid evil" or "sociability") are too abstract and general, which makes their practical application difficult without subjective interpretations. There is no universal consensus on what constitutes "human nature" or the "good."

  • Cultural and historical relativism: The principles of natural law, although presented as universal, often reflect the cultural, religious, or historical values of a specific era or society, which calls into question their supposed universality.

  • Difficulty in resolving practical conflicts: Natural laws, being general principles, do not offer clear mechanisms for resolving specific conflicts or concrete cases, which limits their usefulness in legal practice.

Response from natural law (iusnaturalism):

  • Vagueness allows flexibility to adapt the principles to historical contexts.
  • The connection between law and morality is necessary to avoid unjust laws (for example, Nazi laws, slavery, etc.).
  • The principles of natural law have inspired advances in human rights.
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Categories: Home -> Political Science

Last updated: 2026-04-09

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