Aquinas’s Views on Law

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Jeffrey Thayne

According to Letwin, Thomas Aquinas’s work was designed to reconcile scriptural truth with the philosophy of Aristotle. The assumption here is that Aquinas was attached to Aristotle’s philosophy, and tried to reconcile it with revealed truth. This is an important way to understand Aquinas, but it is not the only way to understand him.

In Response to Augustine

Thomas Aquinas. According to Thomas Aquinas, government is necessary even in a godly society, just as a captain of a ship is necessary not only to punish disobedient sailors, but also to direct obedient ones.

Dr. Reynolds suggests an alternative way to interpret Aquinas’s writings: Aquinas may be responding to the previous eight centuries of Augustinian thought. Characteristic of Augustine’s philosophy is a focus on the Fall; man is fallen, and has lost touch with the divine. In Augustine’s worldview, heaven and earth are irremediably separated. The consequences of the Fall may be mitigated by government force, but government force itself is not qualitatively different than the crime it punishes. Government, in this sense, is an inescapable, necessary evil. It keeps us from being killed by using force against those who would kill us. Human law is an “instrument of repression” (albeit a necessary one), and is thus a product of the fall, just as much as it is necessitated by the fall. To claim that a human law can be patterned after divine or eternal laws is silly, because human law is product of sin, and only necessary because of sin.

Aquinas responded to this worldview with a much more hopeful picture of mankind. He wanted to “bring heaven and earth closer together,” so to speak. Aristotle happened to be a useful tool of doing so. Thus, from Dr. Reynolds’ point of view, Aquinas used Aristotle to develop a more hopeful philosophy in response to Augustine—he didn’t just develop his philosophy to justify his love of Aristotle, as some have claimed.

Government is Part of the Divine Order

Aquinas believed that government is not always the product of the fall, as Augustine did. Aquinas believed that proper government was an important part of God’s overall order in the universe. It wasn’t just an instrument of repression, designed to restrain the violent (although it did serve this purpose); rather, it was a necessary part of even a righteous society, just as a ship needs a captain even if all the members of the crew are skilled and disciplined. As Letwin explains, Aquinas believed that law serves righteous men “more as a plan for unity than as a restraint to passion.”1 Only to those who are not disciplined is the law “a deterrent and an educational device.”1

Certainly, this is a much more positive view of not only law, but also of mankind. We may have unruly members of the crew, but we also have skilled and disciplined members as well; the captain of the ship can discipline the unruly as well as direct the faithful, and in fact is necessary to do both. In the same way, a government can pass laws to restrain criminality, but also to bring order and direction to the community at large. Also, we are not completely cut off from divine reason as to what laws are good, and which are not. There are standards we can measure them by. Government can be an instrument of good, and is a natural part of the order of the universe, not an unnatural diversion from the natural order.

Aquinas speaks of four different kinds of law. He calls these eternal law, natural law, human (positive) law, and divine law.

Eternal Law

What does Aquinas mean by eternal law? Aquinas said:

A law is nothing else but a dictate of practical reason emanating from the ruler who governs a perfect community. Now it is evident, granted that the world is ruled by Divine Providence … that the whole community of the universe is governed by Divine Reason. Wherefore, the very Idea of the government of things in God the Ruler of the universe, has the nature of a law. And since the Divine Reason’s conception of things is not subject to time but is eternal, according to Prov. 8:23, therefore it is that this kind of law must be called eternal.2

I believe that what Aquinas means is simply this: God governs the whole universe in an orderly, lawful fashion. This is eternal law (eternal, in reference to God’s point of view). There is a little bit of mysticism here; we cannot know all of the eternal law, because we do not know the mind of God. However, we can know a portion of it. This leads us to natural law.

Natural Law

Everything in the universe is governed by eternal law; from this this law “being imprinted on them, [things] derive their respective inclinations to their proper acts and ends.”2 However, Aquinas said,

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 itself 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. Hence the Psalmist after saying (Ps. 4:6): “Offer up the sacrifice of justice,” as though someone asked what the works of justice are, adds: “Many say, Who showing good things?” in answer to which question he says: “The light of Thy countenance, O Lord, is signed upon us”: thus implying that 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. It is therefore evident that the natural law is nothing else than the rational creature’s participation of the eternal law.2

In other words, natural law is simply that portion of the eternal law that directs us as rational creatures; it is that part of eternal law that pertains to us, and which we naturally know by being rational creatures. Natural law, according to Aquinas, can be considered a subset of eternal law, or man’s participation in eternal law. This law is the same for all people. In response to the question, “Why do people then disagree on the issue, if it is self-evident and the same for everyone?”, Aquinas responds:

In speculative matters truth is the same in all men, both as to principles as to conclusions, but only as regards the principles which are called common notions. But in matters of action, truth or practical rectitude is not the same for all, as to matters of detail, but only as to the general principles.2

Essentially, the general principles are known to all (except those “perverted by passion, or evil habit, or an evil disposition of nature”; thus, most men don’t kill or steal, but you do have a few madmen here and there), but practical applications may differ. Homogeneity is found only on the level of abstraction; on matters of application, heterogeneity may prevail. “Although there is necessity in the general principles, the more we descend to matters of detail, the more frequently we encounter defects.”2 This is where we learn about human law.

Human Law

This is where we see Aquinas expand on Aristotle’s philosophy. Letwin explains Aristotle’s philosophy: “In Aristotle’s picture, legislators are not obliged to copy an ideal, but rather to articulate in more particular and concrete terms what they have grasped as an abstract requirement. … Aristotle accordingly distinguishes between theoretical and practical reason.”1 This disintction between theoretical and practical reason is preserved in Aquinas’s philosophy. Aquinas said,

We conclude that just as, in the speculative reason, from naturally known indemonstrable principles, we draw the conclusions of the various sciences, the knowledge of which is not imparted to us by nature, but acquired by the efforts of reason, so too it is from the precepts of the natural law, as from general and indemonstrable principles, that the human reason needs to proceed to the more particular determination of certain matters. These determinations, devised by human reason, are called human laws, provided the other essential conditions of law be observed.2

In other words, human law is natural law applied to local and various circumstances. Why must we have human laws, if the natural law is commonly known to all? Because “man has a natural aptitude for virtue; but the perfection of virtue must be acquired by man by means of some kind of training.” Not all have an equal disposition to do good. Some people need to be “habituated” towards virtue; if not at first by natural disposition, then at first by fear of punishment which will later do by natural habit. Thus, it is a practical necessity to enforce laws by punishment, as a means of education.

All (proper) human laws are rooted in natural law in some way; there are two main ways this may happen. The first is that human law is rooted in natural law by logical deduction. For example, a human law that prohibits killing is the logical conclusion of the natural law precept: “One should do harm to no man.” Other laws are derived from natural law by “determination,” (Brian Bix points out that this is not determination “in the sense of ‘finding out,’ but rather in the sense of making specific or concrete”3) which are not inevitable conclusions from natural law, but are rooted in natural law nonetheless. For example, while “the law of nature has it that the evil-doer should be punished; but that he be punished in this or that way, is a determination of the law of nature.”2 It is a specific application of natural law; a law created by men to fulfill the natural mandate that men must be punished, but which does not specify how. Thus, these laws may vary from nation to nation, from community; even though they are firmly rooted in, or developed in response to, a natural law which is the same for everyone. An example provided by Brain Bix is that of traffic laws: the natural law mandates that we ought to provide for the safety of others; in response to this mandate of natural law, we form traffic laws to regulate traffic. The natural law, however, says nothing of whether people should drive on the left or right side of the road.3 Thus, these practical applications may differ by locality, even though they are all in response to a universal mandate of natural law.

While human law is a tool to direct the individual towards virtue, Aquinas is clear that “human law does not prescribe concerning all the acts of every virtue: but only in regard to those that are ordainable to the common good.”2 Thus, the educative scope of human law is limited. He said,

Human law is framed for a number of human beings, the majority of whom are not perfect in virtue. Wherefore human laws do not forbid all vices, form which the virtuous abstain, but only the more grievous vices, from which it is possible for the majority to abstain; and chiefly those that are to the hurt of others, without the prohibition of which human society could not be maintained: thus human law prohibits murder, theft and such like.2

This limit appears to be practical; human law is limited because it is designed for the masses. If it were designed for a group of excessively virtuous people, it would prohibit more vices and encourage more virtues. As it is, it only prohibits those vices and encourages those virtues that the majority of people can habitually abide by. “The natural law is a participation in us of the eternal law: while human law falls short of natural law.”2

One of Aquinas’s central requirements of law is that it has to be promulgated. That is, it must be made known to those affected by it. Also, Aquinas believed the best form of government was a kind of monarchy. This is because laws are designed to unify the populace; monarchy leads to unity, while other forms of government may lead to multiplicity. What should we do if a lawgiver (such as a king) passes an unjust law? The only one who should dethrone a king or leader is the one who appointed him. The noblemen, electorate, etc., ought to rescind their appointment of the leader if the leader is destroying law. This is ideal, because Aquinas is cautious not to promote disobedience, because disobedience may lead to even worse tragedy (anarchy).

When is it justifiable to disregard human law? Only in rare instances, said Aquinas. Laws are just when they are “ordained to the common good,” when they do “not exceed the power of the lawgiver,” and when associated burdens are laid in the community equally.2 Likewise, they are unjust when they exceed the authority of the lawgiver, are not ordained for the common good, or when burdens are imposed on the community unequally. Such laws, Aquinas says, “are acts of violence rather than laws,” and “do not bind the conscience, except perhaps in order to avoid scandal or disturbance, for which cause a man should even yield his right.”2 Thus, even when laws are unjust, Aquinas is very careful to say that we ought (as in we are morally obligated to) to obey them if doing otherwise would create disorder and anarchy or, in other words, make things worse than they were under the unjust laws. The only time that we should unequivocally disregard human law is when they contradict divine law; “such are the laws of tyrants inducing to idolatry, or to anything else contrary to the Divine law: and laws of this kind must nowise be observed.”2

Divine Law

What is divine law? Simply this: the revealed mandates found in scripture. Divine law may prohibit or encourage many things untouched by human law. Aquinas explains:

Man can make laws in those matters of which he is competent to judge. But man is not competent to judge of interior movements, which are hidden, but only of exterior acts which appear: and yet for the perfection of virtue it is necessary for man to conduct himself aright in both kinds of acts. Consequently human law could not sufficiently curb and direct interior acts; and it was necessary for this purpose that a Divine law should supervene.2

Simply put: while human law forbids and punishes murder, divine law forbids and punishes hateful thoughts. This is an example of a vice that human law cannot address or punish, and is thus left to divine law. In this way, Aquinas recognizes the distinction Augustine made between divine instruction and human law. Aquinas points out that divine law is not necessarily homogenous across time and space, because they are God’s revealed mandates to particular people in particularcircumstances.


With these four categories of law, Aquinas demonstrates how he believes human law (positive law) can be rooted in natural law. He uses Aristotle’s belief in an orderly universe and his distinction between theoretical and practical reason to explain the relationship between the enactments of a legislature and the requirements of eternal law. Law, according to Aristotle, is an indispensable part of any polis, and is necessary to bring order to the actions of virtuous as well as rebellious citizens. Just as any ship needs a captain, any polis needs law.


1. Shirley Robin Letwin, On the History of the Idea of Law, (Cambridge: Camrbidge University Press, 2005).
2. Thomas Aquinas, Treatise on Law.
3. Brian Bix, Natural Law Theory.

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