Natural law: Aquinas and the tradition, with Protestant and Orthodox responses

Program / Course 22: Christian Ethics / Lesson 1.2

What you will learn

• Explain the natural law tradition as Thomas Aquinas states it, including the four kinds of law.
• Describe the first precept of natural law and the basic human goods that follow from it.
• State how Reformed, Lutheran and Orthodox writers receive or qualify the idea.
• Name the main philosophical objections to natural law and the replies to them.

The big idea

Natural law is the teaching that there is a moral order built into human nature, that reason can in large part know it, and that it binds everyone. Thomas Aquinas gave the classic account, in which natural law is human beings’ sharing, by reason, in God’s eternal law. Catholic teaching holds to it firmly. Protestants and Orthodox writers differ: some accept it with qualifications, some stress how sin clouds it, and some prefer other language. The debate concerns how far morality can be known apart from revelation.

Key terms

Natural law

The moral order that human beings can know by reason and that is rooted in human nature, as God made it.

Eternal law

In Aquinas, God’s wise plan by which he governs all creation.

Divine law

In Aquinas, law given by revelation, in the Old and New Testaments, to guide people to their final end.

Human law

Laws made by human authorities. In Aquinas they are just only if they are consistent with natural law.

Synderesis

In medieval moral theology, the habit of the mind by which the first principles of action are grasped, such as that good is to be done.

Conscience

The act of judgment by which a person applies moral knowledge to a particular action.

Common grace

A Reformed term for God’s goodness shown to all people, including the moral knowledge and restraint found outside the church.

Naturalistic fallacy

A charge, associated with G. E. Moore and David Hume in different forms, that it is a mistake to derive moral conclusions from facts about nature.

Background

The idea that nature carries a moral order is older than Christianity. Greek and Roman writers, especially the Stoics and Cicero, spoke of a law according to nature that holds for all peoples. Paul writes that Gentiles who do not have the law of Moses “do by nature the things contained in the law” and show “the work of the law written in their hearts” (Romans 2:14-15). Christian thinkers read this as evidence that God has given all people some knowledge of right and wrong.

Thomas Aquinas (about 1225 to 1274) set the theme in a long treatise on law in the Summa Theologiae, First Part of the Second Part, Questions 90 to 97. He combined Aristotle’s view of human nature with Augustine’s view of God’s eternal order. His account has been developed ever since by Catholic theologians and philosophers, and it underlies many Catholic documents, including the Catechism. Protestant and Orthodox writers have both used and questioned it.

Step-by-step explanation

Step 1: Four kinds of law in Aquinas

Aquinas defines law as an ordinance of reason for the common good, made by one who has care of the community and publicly made known. He then distinguishes four kinds. Eternal law is God’s own plan governing all things. Natural law is the rational creature’s participation in that eternal law: human beings share in God’s wisdom by being able to grasp what is good for them. Human law is what rulers enact to apply the natural law to particular conditions. Divine law is revelation, given because natural reason is not enough for humanity’s supernatural end and because human judgment is uncertain.

On this account, natural law is not a rival to Scripture. It is part of the same order of divine wisdom. Revelation does not abolish nature but perfects it. In a phrase often quoted from the tradition, grace does not destroy nature but completes it.

Step 2: The first precept and the basic goods

Aquinas holds that the first principle of practical reason is that good is to be done and pursued, and evil avoided. Other precepts follow the natural inclinations of human beings. He names inclinations shared with all living things, such as self-preservation. He names those shared with animals, such as the union of male and female and the rearing of children. And he names those proper to rational beings, such as knowing the truth about God and living in society.

Modern interpreters differ about how to read this. Some, in the older neo-scholastic tradition, read natural law as derived from a view of human nature as a finished design. Others, including the philosophers John Finnis and Germain Grisez and their followers, speak of basic goods such as life, knowledge, friendship, and practical reasonableness, which are self-evidently worth pursuing and which a person must never directly attack. Catholic thinkers debate these readings among themselves.

Step 3: Strengths and limits as natural law thinkers see them

Aquinas says the most general principles are the same for all, but that conclusions become less certain as they become more particular, and that custom and passion can cloud them. He gives examples of peoples who accepted practices contrary to nature. So natural law is not a claim that everyone agrees on everything. It is a claim that moral knowledge is accessible and that disagreement does not prove that nothing is true.

Natural law supports a public argument. If morality is accessible to reason, believers and unbelievers can reason together about justice, human rights and the common good. This is why many Catholic social documents speak to all people of good will, not only to the church.

Step 4: Responses

Reformed theology accepts a natural knowledge of moral law while stressing the effects of sin. John Calvin wrote that the law of God is engraved on all hearts, and that conscience leaves people without excuse, but that sin so corrupts judgment that fallen reason cannot be trusted without Scripture. Reformed writers speak of common grace by which God restrains evil and gives moral insight even to the unbelieving. Some twentieth-century Reformed theologians, notably Karl Barth, were deeply suspicious of natural theology and of natural law as an independent source apart from Christ.

Lutheran theology, with Luther’s doctrine of two kingdoms or two ways in which God rules, has often affirmed that reason can order civil life by natural law while the gospel concerns salvation. Lutheran thinkers differ on how much weight to give it. Many Lutherans also stress that the law shows sin, before it guides life.

Orthodox writers are often less comfortable with the legal framework. They affirm that God’s image remains in people and that the Fathers, including Basil and Gregory of Nyssa, used the language of what is according to nature. But they tend to speak of nature as wounded and needing healing, and of the moral life as growth in the likeness of God, not primarily as keeping a law known by reason. Orthodox thinkers differ about how far the term natural law fits their tradition.

1. What does this view claim reason can know without revelation?
2. Does the argument start from human nature, from basic goods or from God’s law?
3. How does the view account for people and cultures that disagree about morality?
4. How does it describe the effect of sin on moral knowledge?
5. Could a person who does not believe in God accept this account? What would be lost or kept?
6. What practical conclusion about law or conscience does the view support?

Examples

Different perspectives

Catholic

The Catechism of the Catholic Church presents natural law as the light of understanding placed in human beings by God, by which they know what to do and what to avoid. It is universal, unchangeable in its basic precepts and the foundation of civil law. At the same time the church teaches that, given the wounds of sin, revelation is morally necessary so that all can know the moral law readily and with firm certainty.

Reformed

Reformed thinkers affirm that God’s law is known in some measure by all, through conscience, and treat this as the basis for civil order and for the justice of God’s judgment on those who have not heard the gospel. They emphasize that fallen reason distorts this knowledge and that only Scripture and the Spirit give clear understanding. Opinions differ on how much natural law can be used in public argument.

Lutheran

Lutheran teaching holds that God rules both through the gospel and through the law written in creation and conscience, which serves civil order. Luther was suspicious of the use of Aristotle in theology but still valued reason in earthly matters. Lutherans stress that the law, natural and revealed, drives people to Christ more than it makes them righteous.

Orthodox

Orthodox theologians acknowledge a natural knowledge of good written in human beings, as in Romans 2, but typically frame morality in terms of the restoration of the image of God and the passions to be healed. Some Orthodox scholars warn against importing Western legal models, while others find the Fathers’ language of living according to nature a close parallel.

Secular and philosophical

Some secular philosophers defend natural law accounts without appeal to God, tying morality to human flourishing. Others, in the line of Hume and Moore, object that moral conclusions cannot be derived from facts about nature, or that nature contains no purposes. Natural law thinkers reply that human nature is not a bare fact but includes capacities with ends, so that describing it already involves evaluation.

Why it matters

Natural law shapes much of the public language of ethics, from human rights to the Catholic social documents and to debates about conscience and unjust laws. Even those who reject it need to understand it in order to argue with it. And the disagreement among Christian traditions about how far reason can know the good touches questions of how believers should speak to the wider society.

Common misunderstandings

Knowledge check

Think it through

1. Is there any moral principle you think everyone, in every culture, can know? What is your evidence?
2. How would your answer change if you believed that sin deeply clouds moral judgment?
3. Do you think natural law is a good basis for talking with people who do not share your faith? Why or why not?
4. Which tradition’s response, Catholic, Reformed, Lutheran or Orthodox, do you find most persuasive, and what is the best objection to it?

Independent assignment

A one-page account of natural law

In your notebook, write 400 to 600 words. Explain Aquinas’s four kinds of law in your own words, then summarize in a paragraph each how a Catholic and a Reformed writer would apply the idea to the question of whether an unjust civil law binds conscience. Finish with a paragraph naming the strongest objection to natural law and the best available reply. Do not send this to anyone or post it anywhere.

Further study

• Thomas Aquinas, Summa Theologiae Read the treatise on law, Questions 90 to 97 of the First Part of the Second Part.
• Stanford Encyclopedia of Philosophy, The Natural Law Tradition in Ethics Read fully for objections and variations.
• Catholic Church, Catechism of the Catholic Church Read the section on the natural moral law.
• John Calvin, Institutes of the Christian Religion Read the passages on natural knowledge, conscience and the uses of the law.
• Westminster Assembly, The Westminster Confession of Faith Read the chapter on the law of God.
• Romans 2:15 The work of the law written in the heart.
• Psalm 19:1 The heavens declare the glory of God.
• Romans 1:20 God’s invisible qualities known through what is made.