Saying that everyone has human rights is easy. Explaining why is harder. If rights are not simply granted by governments, where do they come from? Philosophers have offered several answers, each with strengths and weaknesses.

Natural rights

The oldest answer is that rights are part of the natural or divine order. For John Locke, God created human beings equal and free, so no one may harm another's life, health, liberty or possessions. The American Declaration of Independence follows this line: people are “endowed by their Creator” with rights.

Strength: it explains why rights are universal and why no government can take them away; they come before and above any state. Weakness: it depends on religious or metaphysical beliefs that many people do not share, which makes it hard to use as common ground in a diverse world.

Human dignity

The UDHR's preamble begins with the “recognition of the inherent dignity” of all members of the human family. Many modern constitutions, such as Germany's, place dignity at the center. The idea is that every person has a worth that does not depend on usefulness, rank or achievement.

The most influential philosophical version comes from Immanuel Kant. In his Groundwork of the Metaphysics of Morals (1785), Kant argued that rational beings are ends in themselves. Things have a price and can be exchanged; persons have a dignity beyond any price. In an 1873 translation, his principle reads: “So act as to treat humanity, whether in thine own person or in that of any other, in every case as an end withal, never as means only.” Torture, slavery and deception violate this by treating a person as a mere tool.

Strength: dignity can be accepted by religious and secular people alike. Weakness: critics say the word is vague enough to be used on opposite sides of the same debate.

Interests and choices

Philosophers also ask what rights protect. Interest theories say a right exists when some aspect of a person's well-being is important enough to place others under a duty. Will (or choice) theories say rights protect a person's control over their own affairs, letting them demand or waive what others owe them. Interest theories more easily explain rights for young children, who cannot yet make such choices.

Capabilities

The capability approach, developed by the economist Amartya Sen and the philosopher Martha Nussbaum, asks what people are actually able to do and to be: to live a normal lifespan, be healthy, be educated, take part in politics, form relationships. A right on paper means little if poverty, illness or discrimination prevent people from using it. This approach helps explain why economic and social rights belong alongside civil and political ones.

Consensus and pragmatism

A last family of answers sets deep foundations aside. When UNESCO surveyed thinkers around the world in the late 1940s, the French philosopher Jacques Maritain observed that people from very different traditions could agree on a list of rights, on the condition that no one asked them why. The philosopher John Rawls later described an overlapping consensus: people with different religions and philosophies can each support the same basic principles for their own reasons.

Strength: practical agreement is possible even without philosophical agreement. Weakness: rights resting on agreement might seem to vanish if the agreement does. Defenders reply that each tradition still holds its own deep reasons, and the overlap is what lets them live and act together.

Worked example: four answers to one question

Why is slavery wrong? Here is how each approach in this level might answer.

• Natural rights (Locke): God made all people free and equal; no one has the authority to own another. Slavery violates a right that existed before any government.
• Dignity (Kant): slavery treats a person as a thing with a price, a mere means to someone else's ends, denying the dignity every rational being has.
• Capabilities (Sen and Nussbaum): slavery destroys a person's ability to choose their work, form a family, move freely, take part in politics, and shape their own life. It crushes nearly every central capability at once.
• Overlapping consensus (Maritain, Rawls): Christians, Muslims, Buddhists, secular humanists and others, each for their own reasons, agree that slavery is wrong. That agreement is enough to ground a firm shared rule.

All four reach the same conclusion. That is common for the most basic rights, and it is part of why those rights command such wide support.

The approaches differ more on harder questions. Is there a human right to a minimum income? A capability theorist may say yes, since poverty blocks so many capabilities. A strict natural rights theorist may say no, since it requires taking property from others. An overlapping consensus may not yet exist. Knowing which foundation someone uses helps you see why they reach their conclusions, and where an argument with them would have to start.