IusNaturalism

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This article is part of the Basic Liberalism Course -> Module 2: Liberalism and its ethical foundations

Definition

The 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 universal, immutable and superior to human laws (positive law), derived from human nature, reason or an eternal divine law.

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

This idea is what historically allowed challenging absolute power: if the King dictates a law that goes against human nature, that law is invalid.

The 4 Fundamental Principles of Iusnaturalism

1. Universality

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

2. Immutability

Unlike human laws (positive law), which change according to the government in power, natural law does not change over time. What was just by nature a thousand years ago (such as the right to life) remains so today.

3. Superiority

Natural law is at the top of the hierarchy. If a law enacted 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. Cognoscibility (Reason)

These principles are not a mystery; they can be discovered by any person through the use of reason. No divine revelation or law degree is needed to understand that killing or enslaving another human being is wrong by nature.

Branches of IusNaturalism

IusNaturalism has 2 roughly defined branches:

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 is evident 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 the observation of human nature. There is no "written" list of what natural rights are. The 2 branches we mentioned earlier (theological and rational) arrive at almost the same conclusion, with minimal differences. From a 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
Pursuit of knowledge and truth
Promotion of the common good
Justice and respect for contracts (to be able to live in society)

Key difference: Iusnaturalism vs. Iuspositivism

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

Characteristic	Iusnaturalism (Natural Law)	Iuspositivism (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.
Relationship with morality	Law and Ethics are united.	Law and Ethics are separate things.

Different Iusnaturalist ideas

There is not a 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 according to the era, but these are the most influential and representative:

Theological and Classical Iusnaturalism

Thomas Aquinas: Defines natural law as the participation of the rational creature in the eternal law (God's reason). He maintains 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 accordance with natural reason.
Francisco de Vitoria: Considers that natural law is a "right reason" in accordance with human nature created by God. He was a pioneer in applying this to the international sphere, defending that all men (including the American indigenous) possess natural rights such as liberty, property and sovereignty simply by being human.

Rationalist and Contractualist Iusnaturalism

Hugo Grotius: He is considered the father of modern iusnaturalism. He proposed that natural law would exist even if God did not exist, basing it exclusively on reason and the sociable nature of the human being.
Thomas Hobbes: Subverts the traditional idea by founding natural law on the instinct of self-preservation. For him, in the "state of nature" man has a right to everything, but life is "poor, nasty, brutish 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 an innate dignity and the duty to assist others.
John Locke: Maintains that men possess inalienable natural rights (life, liberty and property) prior to the State. Government is created through a social contract with the sole purpose of protecting those rights; if the sovereign violates them, the people have the right to 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 surrenders to the community to be "forced to be free" under laws that he himself has given himself.
Voltaire: Defends natural law from a humanist and social reform perspective. For him, natural law translates into freedom of thought, religious tolerance and equality before the law, fiercely opposing torture and abuses of the judicial system of his time.

Other notables from this era:

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

Contemporary Iusnaturalism (20th-21st centuries)

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 iusnaturalism" (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.

Criticisms of IusNaturalism

Vagueness and lack of definition 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 questions 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 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.

Basic Liberalism Course

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Last updated: 2026-04-09

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