True Law – According to the Teaching of St Thomas Aquinas11-min read (inc. footnotes)

St Thomas Aquinas

St Thomas, Universal Doctor – Fr Edward Leen CSSP
The Holy Wrath of St Thomas Aquinas – G.K. Chesterton
On the Five Qualities of Prayer – St Thomas Aquinas
True Law – According to the Teaching of St Thomas Aquinas
St Thomas Aquinas and the Church – His Intrinsic Authority
St Thomas Aquinas and the Church – His Extrinsic Authority
What is Thomism? The Twenty-Four Thomistic Theses

The Fioretti of St Thomas:
Part I: His Life
Part II: His Death
Part III: The Miracles after his Death

In response to the Covid-19 outbreak, governments worldwide enforced draconian regulations, restricting some of the most fundamental liberties of free societies: the right of free association, the right to earn one’s daily bread by honest labour, and even the right to leave one’s own home. They also used the crisis to further violate fundamental rights – such as violating the right-to-life by expanding provision of “home abortion”.

In the face of these violations of the most basic rights, many were extremely compliant, often on the grounds that “it is the law” and must be obeyed.

It will therefore be useful to consider the traditional teaching of the Church on the nature of law.

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Picture: St Thomas Aquinas (Source)

What is law?

St Thomas Aquinas teaches that the following is a complete definition of law. A law is:

“an ordinance of reason for the common good, made by him who has care of the community, and promulgated.”[1]

Everything that conforms to this definition is a law. Nothing contrary to this definition can ever be a true law, no matter what the purported lawgiver may claim.

We will examine each element of the above definition in more detail, but first we will briefly describe the four kinds of laws.

The four kinds of law

St Thomas teaches that there are four kinds of law.

1. The eternal law: by this law God governs “the whole community of the universe” by His “Divine Reason” and “Divine Providence”. St Thomas teaches that “the very idea of the government of things in God the Ruler of the universe, has the nature of a law.”[2] All creation is subject to the eternal law: “all things partake somewhat of the eternal law, in so far as, namely, from its being imprinted on them, they derive their respective inclinations to their proper acts and ends.”[3]

2. The natural law: the “participation of the eternal law in the rational creature is called the natural law.”[4] By this law, imprinted on every human being, we are directed towards our proper natural ends: “the light of natural reason, whereby we discern what is good and what is evil, which is the function of the natural law, is nothing else than an imprint on us of the Divine light.”[5] 

3. The human law: while the natural law directs us in “a general and indeterminate” way, it is often necessary for human happiness for legitimate authority to make “more particular determination of certain matters”.[6] For example, while the natural law is sufficient for us to know that we shouldn’t kill others by poisoning, human law may give more precise regulations on how water companies use certain toxic chemicals. All human law is derived from the principles of the natural law.[7]

4. The divine law: this has been revealed by God to direct us to our supernatural end. St Thomas gives four reasons why a divinely revealed law is necessary:

  • the natural law directs us to natural happiness but not to supernatural happiness[8]
  • our human judgement can suffer from “uncertainty… especially on contingent and particular matters… therefore, that man may know without any doubt what he ought to do and what he ought to avoid, it was necessary for man to be directed in his proper acts by a law given by God, for it is certain that such a law cannot err.”[9]
  • human laws can only regulate external acts. Yet virtue requires also interior acts. Therefore, God commands these internal acts through the divine law.[10]
  • human law cannot punish all human acts, “since while aiming at doing away with all evils, it would do away with many good things, and would hinder the advance of the common good.”[11] “In order, therefore, that no evil might remain unforbidden and unpunished, it was necessary for the Divine law to supervene, whereby all sins are forbidden.”[12]

All four forms of law conform entirely to the definition of law given by St Thomas, namely that law is “an ordinance of reason for the common good, made by him who has care of the community, and promulgated.”[13]

We will now examine each part of the definition in more detail, but with emphasis on its implications for laws promulgated by human beings. The eternal law, the natural law and the divine law are all promulgated by God Himself, for the common good, and in accordance with His Eternal Reason.[14]

A law is an ordinance of reason

“Law” states St Thomas “is a rule and measure of acts, whereby man is induced to act or is restrained from acting”, consequently “it belongs to the law to command and to forbid.”[15]

All truly human acts must accord with reason.[16] Therefore laws, which induce man to act or restrain him from acting, must also accord with reason.[17]

No command contrary to reason can have the nature of law:

“in order that the volition of what is commanded may have the nature of law, it needs to be in accord with some rule of reason.”[18]

Furthermore, as stated above, human law is derived from the natural law, “consequently every human law has just so much of the nature of law, as it is derived from the law of nature. But if in any point it deflects from the law of nature, it is no longer a law but a perversion of law.”[19]

The Triumph of St Thomas over Averroes

A law is ordained to the common good

Laws are always directed to the common good of the community for which they are ordained, whether that be the Church or the state. And the primary end of every law must be the end of human life itself, namely happiness; “the law must needs regard principally the relationship to happiness.”[20] Those civil laws called “just” are those “which are adapted to produce and preserve happiness and its parts for the body politic”.[21]

It follows from this that any command which is contrary to the common good, does not have the nature of law:

“Consequently, since the law is chiefly ordained to the common good, any other precept in regard to some individual work, must needs be devoid of the nature of a law, save in so far as it regards the common good.”[22]

A law is made by legitimate authority

Laws are directed to the common good. Therefore, only the whole community, or those with legitimate authority over the whole community, can make laws.

As Thomas teaches:

“Now to order anything to the common good, belongs either to the whole people, or to someone who is the viceregent of the whole people. And therefore the making of a law belongs either to the whole people or to a public personage who has care of the whole people: since in all other matters the directing of anything to the end concerns him to whom the end belongs.”[23]

If a private person – someone who does not have legitimate authority – tries to make or enforce a law this is null and void.[24]

The force of laws passed by legitimate authority is diminished – and perhaps made entirely null – if the laws they pass are contrary to the universal custom of a people:

“to a certain extent, the mere change of law is of itself prejudicial to the common good: because custom avails much for the observance of laws, seeing that what is done contrary to general custom, even in slight matters, is looked upon as grave. Consequently, when a law is changed, the binding power of the law is diminished, in so far as custom is abolished.

“Wherefore human law should never be changed, unless, in some way or other, the common weal be compensated according to the extent of the harm done in this respect. Such compensation may arise either from some very great and every evident benefit conferred by the new enactment; or from the extreme urgency of the case, due to the fact that either the existing law is clearly unjust, or its observance extremely harmful. Wherefore the jurist says that ‘in establishing new laws, there should be evidence of the benefit to be derived, before departing from a law which has long been considered just.’”

Indeed, custom itself can have force of law:

“Augustine says ‘The customs of God’s people and the institutions of our ancestors are to be considered as laws. And those who throw contempt on the customs of the Church ought to be punished as those who disobey the law of God.’”[25]

Furthermore, if a people are:

“free, and able to make their own laws, the consent of the whole people expressed by a custom counts far more in favour of a particular observance, that does the authority of the sovereign, who has not the power to frame laws, except as representing the people.”[26] 

The Conversion of St Augustine by Fra Angelico (Source)

A law is duly promulgated

Laws by their nature are made for the good of a particular community. Therefore, they must be duly applied to that community to have the nature of law.

As St Thomas states:

“Wherefore, in order that a law obtain the binding force which is proper to a law, it must needs be applied to the men who have to be ruled by it. Such application is made by its being notified to them by promulgation. Wherefore promulgation is necessary for the law to obtain its force.”[27]

The manner of promulgation will differ from society to society.

Do we have to obey an unjust law?

In general, we are bound obey true laws:

“If they be just, they have the power of binding in conscience, from the eternal law whence they are derived, according to Proverbs 8:15: ‘By Me kings reign, and lawgivers decree just things.’”[28]

There will of course be certain circumstances in which even true laws are not binding, for example, laws cease to bind if their application becomes harmful:

“Now it happens often that the observance of some point of law conduces to the common weal in the majority of instances, and yet, in some cases, is very hurtful. Since then the lawgiver cannot have in view every single case, he shapes the law according to what happens most frequently, by directing his attention to the common good. Wherefore if a case arise wherein the observance of that law would be hurtful to the general welfare, it should not be observed.”[29]

But what of laws that do not fulfil the definition of true law?

St Thomas separates these into two categories.

1. “Laws” that are contrary to the “divine law”, such as a law which commands something sinful; “laws of this kind must nowise be observed, because, as stated in Acts 5:29, ‘we ought to obey God rather than man.’”[30]

2. “Laws” that are contrary to a “human good”, but which do not command something intrinsically evil. These “laws” are also unjust and “a law that is not just, seems to be no law at all”. They are “acts of violence rather than laws”. Consequently “such laws do not bind in conscience”, except perhaps in certain individual circumstances, “in order to avoid scandal or disturbance.”[31]


Any purported law, whether made by ecclesiastical or civil authority, which either (a) is contrary to reason, (b) is contrary to the common good of the community for which it is made, (c) is made by an individual lacking legitimate authority or (d) is not duly promulgated, is null and void and has no binding effect.

I suggest that in our times these are important principles to bear in mind.

St Thomas Aquinas

St Thomas, Universal Doctor – Fr Edward Leen CSSP
The Holy Wrath of St Thomas Aquinas – G.K. Chesterton
On the Five Qualities of Prayer – St Thomas Aquinas
True Law – According to the Teaching of St Thomas Aquinas
St Thomas Aquinas and the Church – His Intrinsic Authority
St Thomas Aquinas and the Church – His Extrinsic Authority
What is Thomism? The Twenty-Four Thomistic Theses

The Fioretti of St Thomas:
Part I: His Life
Part II: His Death
Part III: The Miracles after his Death

Supporting The WM Review through book purchases

As Amazon Associates, we earn from qualifying purchases through our Amazon links. Click here for The WM Review Reading List (with direct links for US and UK readers).

Summa Theologica Trans. by the Fathers of the English Dominican Province, (5 vols.) Ave Maria Press, Hardback (and UK readers) and Paperback (and UK readers). Also online at New Advent and iPieta.

Summa Theologiae, Aquinas Institute (8 vols.) Latin-English, based on the English Fathers’ translation, without the Supplementum parts. (And for UK readers) Supplementum I-68 (and UK readers) Supplementum 69-99 (and UK readers)

St Thomas Aquinas – Summa Contra Gentiles. Aquinas Institute in 2 vols: Vol. I (Books I-II) and Vol. 2 (Books III-IV) and for UK readers here and here. Budget single-volume from Aeterna Press (and for UK readers) and online at iPieta or

Aquinas – Opuscula I, from the Aquinas Institute (UK readers), containing the following:

St Thomas Aquinas – Catena Aurea (and for UK readers). 4 vols, line-by-line commentary on the four Gospels from the Fathers of the Church, assembled by St Thomas Aquinas and translated by Cardinal John Henry Newman. Published by Baronius Press.

Tradivox VI: Aquinas, Pecham, and Pagula (UK readers), including St Thomas Aquinas’s Catechetical Instructions. An arrangement of other Opuscula in catechetical form. (ca. 1260)

St Thomas Aquinas’s scriptural commentaries are being published by the Aquinas Institute in English and Latin. Here are some of the options below – they are online here, and it is possible to buy single volumes of the commentaries below:

Anger – The Doctrine of the Mystical Body According to the Principles of St Thomas Aquinas (and for UK readers). Internet Archive. Draws together several texts for which there is a bit of a lacuna in the Summa itself.

Glenn – A Tour of the Summa. A compressed one-volume account of the Summa. (UK readers)

Pegues – Catechism of the Summa Theologica for the use of the Faithful (and for UK readers)

G.K. Chesterton – St Thomas Aquinas. Classic biography. (UK link)

Foster – The Life of St Thomas Aquinas – Biographical Documents (UK readers). Online at Internet Archive.

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[1] St Thomas Aquinas, Summa Theologica, II. I q.90 a.4

[2] II. I q.91 a.1

[3] II. I q.91 a.2

[4] II. I q.91 a.2

[5] II. I q.91 a.2

[6] II. I q.91 a.3

[7] II. I q.95. a.2

[8] II. I q.91 a.4

[9] II. I q.91 a.4

[10] II. I q.91 a.4

[11] II. I q.91 a.4

[12] II. I q.91 a.4

[13] II. I q.90 a.4

[14] II. I q.91 a.1-4

[15] II.I q.90 a.1

[16] II. I q.1 a.1

[17] II.I q.90 a.1

[18] II.I q.90 a.1

[19] II. I q.95. a.2

[20] II. I. q.90 a.2

[21] II. I. q.90 a.2

[22] II. I. q.90 a.2

[23] II. I. q.90 a.3

[24] II. I. q.90 a.3

[25] II.I q.97 a.3

[26] II.I q.97 a.3

[27] II. I. q.90 a.4

[28] II.I q.96. a

[29] II.I q.96 a.6

[30] II. I. q.96 a.4

[31] II. I. q.96 a.4

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