St. Thomas Aquinas’ Contributions towards Law

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Amidst all the eminent scholars like William of Ockham, Duns Scotus, Averroes and other philosophers, St. Thomas Aquinas was one of the greatest scholastic philosophers of his time. He was one amongst the first and foremost of theologians to walk on Medieval Italy whose contributions towards the study of Law, Philosophy, Theology and etc., are humongous, also the founder of Thomistic School of Philosophy and Theology which had subsequently exerted enormous influence on Christian theology, Roman Catholic Church in particular and western philosophy in general. Dominican friar Thomas Aquinas lived in the era where the ancient learning of Greek-Roman thinking was trampled as paganism and the practice of church seemed to be the only authentic practice in society. Aquinas’ well-known discussion of law in his book, Summa Theologiae, especially from the questions 90-97, had been justly admired by jurists and other scholastic thinkers unanimously.

Aquinas was born in Italy in 1225 to a huge family. He had eight brothers and sisters! He spent his childhood in a Benedictine monastery and went to study there when he was just five years old. After that, he returned to Naples, Italy, where he studied the work of the philosopher Aristotle. Nine years later he entered the University of Naples, becoming acquainted there with the Dominican order, which he joined when he was about 20 and continued to study religion, which was a different order than the one his family supported.

Aquinas’ Summa Theologiae with respect to Philosophy of Law

Aquinas’ importance emerges with his deep interpretation of theology under the thread of Aristotelian philosophy. He was the first western theologian to use Greek philosophy analytically in order to develop theological arguments. It was only after Aquinas’ theological revolution during the 13th century, for the first time the western intellectual tradition had come to admit the existence of a hierarchy of laws though it was constructed for the sake of theological justification of God. Until then the general public adhered the concept of law and human domination had been rooted in and around sin.

It was in Summa Theologiae aka Summary of Theology, a masterpiece that has left a hallmark legacy in the world of Law, Ethics and Philosophy. In a specific chapter called Treatise of Law, he attempts to solve the mystery, ‘what is law’ and is in the form of a list of questions in resolving the riddle. In question number 90, Aquinas questions the nature of law, he states, ‘It seems that Law is not a product of reason. Paul says in Romans, I see another law at work in my body. But there is no reason in my body since reason doesn’t make use of a bodily organ. So the law is not a product of reason.’ 1Certainly, he analyses law in the eyes of logical reasoning and comes into articulation with binary oppositions. For instance, while expressing law as a product of reason, he raises the objection to his own theory, criticising, ‘Law is a standard of measurement; there are two ways it exists in things. Firstly in what does the measuring and regulating, and since that is the proper role of reason law in this sense exists in reason alone.’ Just like Aristotle, Aquinas also believes that reason is one of the fundamental principles which give shape to the earthly journey of a man.

And in question 98, Article 5, he had taken the position of Old Testament Law where he states, ‘the old law showed forth the precepts of the natural law’ interestingly the moral precepts that he had aforementioned were akin to the Decalogue (or the Ten Commandments in Old Testament). Further, in question 99, Aquinas argues that the moral precepts of natural law actually derive their binding force from reason itself. Now here comes the billion-dollar question in Jurisprudence, ‘If natural law was meant to be natural, why do people need a dictum?’

To answer this question, let’s take a deeper look. Aquinas resonates, ‘Man was proud of his knowledge’ and accordingly in order that his pride may overcome, the man was left to the guidance of his reason without the help of a written law. Ultimately, the man had come to learn from experience as his reason was deficient, and since the age of yore, man has fallen headlong into sin. Thus, it was necessary for a written law to be given as a remedy for human ignorance because by the Law is the knowledge of Sin, his writings affirm the fact how Aquinas incorporated Old Testament laws into his natural law philosophy and it further indicates the validity of written law as a legal code to subordinate man. Although the reason is important to choose good from evil, Man’s original sinfulness can hinder the reason. 2Hence we need a dictum, i.e., written law to give a touch of life for men. As we can see, Aquinas had used the Ten Commandments in the Old Testament in order to bring about the realization of the idealistic position of Natural Law to the world.

Categorization of Laws

One of the important views moulded by Aquinas in west jurisprudence was his classification of types of laws. Question 91 of Summa Theologiae predominantly deals with the aspects of laws. He recognizes the hierarchy of laws, explicitly as, the eternal, the natural, the human and the divine, respectively. Indeed the understanding of his types of laws is relevant mainly due to the common misconception of Thomistic law as one single unit, while it isn’t.

Eternal Law

Eternal Law is the ideal order and design of the universe in the mind of God as seen by God himself. Theology scholar, Timothy McDermott had illustrated Aquinas’ view on eternal law as a metaphysical concept which mainly includes two aspects. Firstly, in a transcendental way and secondly, in an utterly ineffable way that is integrated with its mysterious divine nature.

Natural Law

Natural Law is filled with moral content and is more general in nature as it deals with the necessary rather than the variable things. Natural law holds that in general, human life out to be preserved and steps should be taken in order to do the needful. Aquinas in his book, Summa Theologiae defines Natural law as, ‘Now among all others, the rational creature is subject to Divine providence in the most excellent way, in so far as it partakes of a share of providence, by being provident both for it and for others. Wherefore it has a share of the Eternal Reason, whereby it has a natural inclination to its proper act and end: and this participation of the eternal law in the rational creature is called the natural law’ Certainly, Natural Law was understood by Aquinas as a parallel to the line of argument that was developed by St. Augustine, as he had expressed in ‘The City of God’ Aquinas too believed that man’s ultimate aim should be the realization of Lex Aeterna (Divine Law) as a priori. In actual fact, Lex Naturale (Natural law) was seen as a subjective constituent that man should attain in particular since the fall of man he had been excluded from the grace of man and in such a situation, natural law becomes the only console to conquer grace of God. This seems to signify that Aquinas has taken the theological view to flourish the idea of natural law, as he states, Lex Naturalis est scripta in cordubus Ominum, meaning ‘Natural Law is written in the heart of Man.’

Divine Law

Divine Law is derived from the eternal law as it appears historically to human beings as it appears to them as divine commands. The divine law consists of two facets, namely the Old Law and the New Law more or less corresponding to the Old Testament of the Ten Commandments and the Teachings of Jesus, respectively. The Old Law commands over the external behaviours of human beings that reach through their capacity for fear and aims at giving social peace and security and promises earthly rewards. The New Law commands over the internal conducts that reach humans beings through divine love that promises heavenly rewards.

Human Law

Aquinas in his book Summa Theologiae further states in question 91, article 3 that ‘The human law is to enable disabled persons to follow the dictates of the natural law.’ This prominent phrase justifies the supremacy of natural law over human law which is worthy to mention here, ‘The first rule of reason is the law of nature, consequently, every human law has just as much of the nature of law, as it is derived from the law of nature’ Originally, this line is a semblance of what Augustine had stated in his work, the City of God, Lex iniqua lex non est, meaning ‘An unjust law is no law at all.’ We can say that Law is directed towards the common good and Human la is no exception. Human laws are laws that are devised by human reasoning with regards to particular historical, social and geographical circumstances that promote virtue that is necessary for the political community’s common good.

According to Aquinas, the human law was not wholly a philosophical reflection, but also deliberately deals with the mundane affairs of everyday life; the issues that concern a common man’s life, in particular, have been attended to by constructing a system of laws that governs the peripheral behaviour of a man. In contrast to the eternal law, human law is neither absolute nor unchangeable as they’re practical matters that gradually advance from being imperfect to perfect.

Critical Analysis – Silhouette of Aquinas in the Modern Natural Law theory

Traces of St. Thomas Aquinas’ influence on the western legal system continued till the end of the middle age, the European ecclesial orders, in particular, had kept the ‘Thomistic Ideology’ on la as a part of their prospectus. The natural law philosophy of Aquinas made an insightful weight on the works of Niccolo Machiavelli in early 15th century Europe. He emphasises the Thomistic notion of natural law and its relevance of governing the populace.

However, the significance of Aquinas’ understanding on natural law began to wither away with the rise of a nation-state system and in jurisprudence its grandeur as the cardinal legal theory was exceeded by 19th century Austinian concept of the depiction of law as sovereign’s command. This blew off the conventional understanding of Aquinas’ natural law philosophy as a less significant or rather a mere theological fragment.

The revival of Thomas Aquinas’ discourse was started with the end of Second World War and inception of the Nuremberg trial which fervently insisted on the validity of human reason over obedience to the authority. The modern defence of the Thomistic notion of natural law is attributed to an Oxford legal philosopher called John Finnis. He has been able to revisit the Aquinas‟ old theory of natural law and revive it on a contemporary ground. In 1980 Finnis published Natural Law and Natural Rights which was intended to be a theoretical analysis of how he grasped Thomistic ideas into the contemporary version of natural law. In general viewpoint, the Aquinas had said an unjust law is no law at all (Lex injusta non est lex). But Finnis has pertinently elaborated on this version of Aquinas. He argues Aquinas only quoted what Augustine said and he never completely denied the authoritative laws which meant to be harsh or evil in its nature.  Instead of Aquinas portrayed bad laws or unjust law as a perversion of the law. Under this conjecture, it is evident that a system of law according to the state of affairs could exist though it looks harsh in nature but when it comes to the core aspect, the law should be focused on common good.3

The most recent example based on Thomistic influence can be seen in the work of a notable Indian Economist Amartya Sen. In Sen’s ‘The Idea of Justice’ he has spoken of the person’s basic sympathy. He argues in many cases basic sympathy can do good for others in a spontaneous way. In fact, the idea of basic sympathy only arises from the aged long Thomistic understanding of Goodness. This is only one illustration that would demonstrate how profoundly Aquinas’ idea on law and justice has made its impacts on the ideas of modern-day scholars.


Aquinas’ contribution to law and justice in the modern world has left a hallmark legacy, though it has been subjected to many criticisms. Aquinas’ idea of types of laws has duly conceived the notion of natural law. It is true that his understanding of natural law was heavily influenced by Aristotelian philosophy, but Aquinas developed his own philosophy towards natural law. It later prevailed for many centuries while enabling the other school of thoughts to generate other counter philosophical traditions. Moreover, Thomistic contribution to natural law reaches its pinnacle with his unique concept based on justice.

The western idea of justice dates back to the Greek era and in the time of Thomas Aquinas, both Greek-Roman analogies were interwoven with the idea of justice. Being an admirer of Aristotelian thinking Aquinas developed his own idea of justice a little further. He defined justice to mean justice according to divine reason. However, justice fell within the purview of reason. This conception ignited many later modern legal scholars to take the idea of justice in a novel approach. Besides his staunch conviction on God, his interpretation of natural law was not completely faded by the theological influence and it had mainly caused the development of a specific thinking system by bringing many new philosophical insights. It may be true to state that Aquinas’ own understanding on – natural law had many defects in its philosophical enrichment and it only became a moot point to legal positivists critique and develop their own narrative on the law. 4But despite having so many drawbacks the cardinal validity of his ideas on natural law prevailed over many centuries while bringing new insights into the Western jurisprudence.


1.  Chee-Jae Shin, ‘The Thomas Aquinas’ Thought of Natural Law and Justice – Theological and Philosophical Basics of his Thought of Law – (2014) 16 CHUNG_ANG LAW REVIEW

2.  Frederick A. Collins Jr. & Anton-Hermann Chroust, The Basic Ideas in the Philosophy of Law of St. Thomas Aquinas as Found in the “Summa Theologica” – (1941) MARQUETTE LAW REVIEW

3.  Punsara Amarasinghe, ‘Evaluating St, Thomas Aquinas’ Contribution to Nature Law’ – (2017) RESEARCHGATE

4.  Brendan F. Brown, ‘The Influence of St. Thomas Aquinas on Jurisprudence’ – (1957) THE CATHOLIC LAWYER


Meera Bharathi S

Student, Tamil Nadu National Law University

Meera Bharathi is a curious and enthusiastic person who loves writing. She has co-authored a few anthologies. She believes that a legally empowered society can pave the way for a better environment for the people to live in. For any clarifications, suggestions and feedback kindly find her at

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