Natural law

by Dr Joseph Shaw


St Thomas Aquinas’s understanding of natural law was the dominant moral theory prior to modernity. Although his formulation of the subject is considered to be definitive, the natural law tradition evolved over the centuries from the pre-socratics to the medieval scholastics. 

In this course, Dr Shaw explains the origins of the natural law tradition in ancient Greek philosophy, its role in the thinking of St Thomas Aquinas, its rejection, in the eighteenth century, by some key figures of the Enlightenment, and what subsequently took its place. 

St Thomas Aquinas understood the natural law in the context of eternal law, human law, and ecclesiastical law, as well as our place in creation as rational creatures, and the relationship between the individual, the Church and the state. St Thomas combines an approach to ethics focused on the virtues with an acknowledgement of the importance of duty and moral obligations.  

By examining what happened after Aquinas, we will see the difference between the classical Catholic approach to ethics and the approaches of modern theories, and ways in which natural law can be used to approach practical moral questions today.



Dr Joseph Shaw




Course programme

In the first lesson, Dr Shaw shows the roots of the natural law tradition in the fourth century BC. Plato and Aristotle’s rejection of the amoralism of the sophists and the importance they placed on human nature would go on to be shared by the stoics of the early Christian era. Then, three centuries later, St Augustine of Hippo synthesised these diverging philosophical traditions with that of Christian revelation and natural law took shape.

DATE: Tuesday 11 October 2022
TIME: 18:00 (UK time)


St Thomas Aquinas defined natural law as the participation of rational creatures in the eternal law: the collection of basic principles, established by God, of how created things work. Rational creatures can participate in this in a special way since they can understand the ends they seek. However, while humans seek natural happiness, the grace of God has also made us capable of supernatural happiness.

DATE: Tuesday 18 October 2022
TIME: 18:00 (UK time)

Aquinas sees humans as seeking happiness, either correctly or incorrectly, by a natural disposition. This disposition must be combined with the observance of moral rules, which deter us from  certain actions  — e.g. killing the innocent, adultery — which are incompatible with natural and supernatural happiness; that is, of friendship with God. These moral rules are to be understood in terms of the intentions of our actions, but their side-effects are also morally important.

DATE: Tuesday 25 October 2022
TIME: 18:00 (UK time)


Eternal and natural law are supplemented by divine law and human, positive law. The functions of these laws and how they interact is important. It should be kept in mind that, in Aquinas’ day, the power to create laws was not exclusive to the state: the Church and many other institutions imposed obligations which could be enforced, and people imposed duties on themselves by taking vows and oaths.

DATE: Tuesday 1 November 2022
TIME: 18:00 (UK time)


In the eighteenth century, protestant hostility towards the aristotelian and thomistic traditions bore fruit in new philosophical theories of ethics. David Hume’s theory replaced rational action with psychological compulsion, whereas Kant rejected habit and character in favour of rational consistency. In political theory, the key concept became consent. Enlightenment ethics has had to contend with the denial of human freedom and the complete rejections of morality.

DATE: Tuesday 8 November 2022
TIME: 18:00 (UK time)


Natural law ethics is associated today with teleology, which explains phenomena such as the sexual act, marriage, and human nature in general in terms of their end or purpose. This needs to be set into the wider context of the kind of moral objectivity supported by the natural law tradition: that some things are worth doing or having, such as knowledge of the external world. It implies a set of obligations which we inherit, and cannot repudiate.

DATE: Tuesday 15 November 2022
TIME: 18:00 (UK time)


Dr Joseph Shaw

Joseph Shaw is a philosopher and author. For many years he was a senior research fellow at St Benet’s Hall, Oxford and a member of the faculty of Philosophy. He is a fellow of the Royal Society of Arts, chairman of the Latin Mass Society, and president of the Una Voce International Federation. He has a doctorate in philosophy, a diploma in theology, and a bachelor's degree in politics and philosophy.

He has published on academic philosophy, the traditional Catholic liturgy and on Catholic culture and politics. He edited The Case for Liturgical Restoration: Una Voce Studies on the Traditional Latin Mass (Angelico Press, 2019). His work has been published by the European Conservative, the Catholic Herald, the Voice of the Family Digest and Calx Mariae, and in many other publications, and he has his own blog:

He lives in Oxfordshire with his wife and nine children.


Plato, Gorgias

Aristotle, Nicomachaean ethics, book 1&2

Augustine, De mendacio (“On Lying”)

St Thomas Aquinas, Summa theologica

1a 2ae, Q. 5, a.3&5Whether goodness is prior in idea to being?
1a 2ae, Q. 91, a.1&2Whether there is an eternal law?
1a 2ae, Q. 94, a.1&3Whether the natural law is a habit?
1a 2ae, QQ. 95 Of Human Law
1a 2ae, QQ. 96 Of the Power of Human Law
1a 2ae, QQ. 97 Of Change in Laws

Ralph McInery, Ethica Thomistica: The Moral Philosophy of Thomas Aquinas (Catholic University of America, 1997)

David Hume, Treatise on Human Nature, book 3, part 1; part 2, sections 1 and 2.

Immanuel Kant, Groundwork for the Metaphysics of Morals, first section.

J.S. Mill, Utilitarianism, chapter 1

Elizabeth Anscembe, “Modern Moral Philosophy” (1958)

John Finnis, Natural Law and Natural Right (1980)

Sherif Girgis, Robert George & Ryan Anderson, “What Is Marriage?” (2010)