The Libertarian Aquinas: Aquinas, Libertarianism, and the Definition of Law (Part 2)

Jonathan McIntosh (Ph.D., University of Dallas) is a Fellow of Humanities at New Saint Andrews College in Moscow, Idaho, where he teaches on the history of western political and economic thought, philosophical theology, natural law ethics, Aquinas, Anselm, and J.R.R. Tolkien. He is the author of The Flame Imperishable: Tolkien, St. Thomas, and the Metaphysics of Faërie, and blogs at The Natural Law Libertarian and The Flame Imperishable

In the first post in this series, I outlined some of the ways in which the influential political thought of St. Thomas Aquinas (1225-1274) both conflicts and comports with libertarianism. This post is the first in a series undertaking a closer examination, from a libertarian perspective, of Aquinas’s celebrated “Treatise on Law” from his most well-known and greatest work, the Summa Theologiae. In the opening chapter, or “question,” of his “Treatise on Law,” Aquinas sets out to define what law is by asking four fundamental questions: (1) what kind of thing is law? (2) what is the purpose or end-goal of law? (3) who can make and impose law? and (4) must law be promulgated? His answers to each of these questions comprise his famous, four-part definition of law: law is “an ordinance of reason, for the common good, made by one with care of the community, and promulgated.” Although Aquinas intends his definition of law to apply to far more than merely human law, including divine and natural law, in this post we will be considering each part of his definition of law specifically as it applies to the civil realm, along with what a libertarian response might be.

What is law? Aquinas argues that law is an “ordinance of reason,” meaning that it is something that reason itself orders, commands, or directs human beings to do (ST I-II.90.1). The idea here is that law regulates human action, but normally, in everyday life, the way in which human beings regulate their actions is by means of their reason. If law, therefore, is to accord and not conflict with our human nature as rational beings, then Aquinas’s point is that law must belong to that order of things that reason itself directs us to do.

While the libertarian might want to clarify precisely which commands of reason are to be made a matter of law (principally those prohibiting acts of aggression), the fact that law should be an ordinance of reason he would scarcely wish to disagree with. In contrast, for example, with the legal positivism dominating much jurisprudence today, according to which law is whatever rules have been established and enforced by those in political authority, for Aquinas, law is never merely law because of some government’s or ruler’s say-so, but is authoritative only so far as it may be seen to participate in an objective, rational order by which human actions are directed to recognizably human ends. The authority of law is, and must be, the authority of reason.

Where Aquinas and the libertarian begin to part ways is in his answer to his second question about law: what is the purpose of law (ST I-II.90.2)? Because all human action is directed by reason to man’s ultimate end of human happiness or flourishing, and law belongs to reason as a means of directing human action, Aquinas concludes from this that the end of law is not any individual’s private or particular good, but the common good of a community’s shared or “universal happiness.”

Taken by themselves, Aquinas’s view that all human action and hence law are ultimately ordered to happiness, and that the end of law is the common good, are not at all inconsistent with libertarianism. For the libertarian, after all, the end of law is the protection of individuals from acts of aggression, an end that is clearly a common good in Aquinas’s sense of the term, and one that he would certainly include as at least a part of the common good brought about by law. Where the libertarian would disagree, rather, is with Aquinas’s claim that the common good aimed at directly by law, giving it its immediate, proper, or distinguishing end, is specifically the community’s shared happiness or well-being. Why should this be assumed to be law’s defining goal? Significantly, Aquinas utterly fails to shows that this is the case, for from the premise that all human actions and law are ultimately ordered to the end of human happiness, it does not at all follow that law is, as he puts it, “chiefly and mainly” concerned with happiness. On the question of the defining purpose of law, then, the place where the libertarian breaks with Aquinas is precisely where Aquinas’s own argument breaks from reason.

Aquinas’s third question for law asks who is in a position to make law, with Aquinas’s answer being that only the whole community, or else its appointed representative, can make law (ST I-II.90.3). Here Aquinas implies something the libertarian would also affirm, namely that the authority to make law lies foundationally with the people, and that the only authority governments or rulers have to make law is an authority conferred upon them by the people. Unfortunately, what Aquinas doesn’t address is where the people themselves get their authority to make coercive law. For the libertarian, a people’s right to make coercive law is simply a consequence of its individual members’ right, in the absence of government, to use force to defend themselves or others. Something Aquinas does address, however, is the question of why individuals cannot make law, given that individuals are able to direct each other to the kind of virtue and hence happiness that law also aims at. Aquinas’s answer is that individuals do not have the right to use coercion to force people towards virtue the way that law does, a claim that the libertarian would not only strongly oppose, but which, as we shall see in subsequent posts, contradicts Aquinas’s own later express denial that law is an effective means of bringing about virtue (see ST I-II.95.1 and 96.2).

The fourth and final part of Aquinas’s definition of law is that it needs to be promulgated (ST I-II.90.4), a requirement that, on the one hand, rightly excludes such unjust and tyrannous practices as ex post facto laws (laws criminalizing and punishing behavior after the fact) and secret laws. On the other hand, the libertarian might rightly ask whether Aquinas’s promulgation requirement would be quite so necessary if law were properly limited by the non-aggression principle in the first place, a principle whose truth is (as Aquinas’s own understanding of the largely non-aggressive “law of nations” would suggest) already a matter of universal, natural-law “promulgation.”

Much more could be said, both pro and con, by way of a libertarian evaluation of Aquinas’s famous and influential definition of law, but the foregoing gives at least the broad outlines of where the two traditions stand with respect to each other. For the libertarian, as for Aquinas, law is an ordinance of reason, for the common good, made either by the community or its representatives, and promulgated. For each part of this definition, however, the libertarian would add important qualifications and, in places, even corrections: law is a command of reason, but a command of reason specifically as it concerns the use of coercion, something Aquinas omits from his definition here but includes in it elsewhere (ST I-II.96.5). Law, for the libertarian, is also ordered to the common good, but not the common good of a shared, “universal happiness,” which Aquinas himself fails to show, but the much more limited common good that is both morally and practically achievable by coercive means, namely the protection of persons and property from acts of aggression. Libertarian law is also law made by the community, but because the community is composed of individuals, the community has no right to make coercive laws that go beyond the coercive rights of its individual members. And law, finally, must be promulgated, but in keeping with Aquinas’s first point about law’s rationality, law also ought to be limited to that (non-aggression) principle which reason itself has already universally promulgated to all men.

In the next post, we will undertake a libertarian evaluation of the next section in Aquinas’s “Treatise on Law,” which contains his equally famous and influential division of law into its four principal kinds: eternal law, natural law, human law, and divine law.

LCI posts articles representing a broad range of views from authors who identify as both Christian and libertarian. Of course, not everyone will agree with every article, and not every article represents an official position from LCI. Please direct any inquiries regarding the specifics of the article to the author. 

Interested in Contributing? 

LCI accepts guest submissions by high-quality writers. If you are interested in submitting a guest post, click here to send us mail.

Don't Miss an Article! Sign up Today!

Whenever there’s a new article, you’ll get an email once a day! 

*by signing up, you also agree to get weekly updates to our newsletter

The Pandemic Bites

Libertarian Christian Answers to Questions about the Pandemic

Sign up for our new email series, and we’ll  share some bite-sized writings with you that discuss various aspects of the pandemic. We will address economics, science, politics, and ethics in accessible chunks with helpful references to learn more.

You’ll away having learned something new and useful as we continue to work past these difficult times together.*

*by signing up, you also agree to get weekly updates to our newsletter


Never Miss A Story

Get our Weekly recap with the latest news, articles and resources.

Current Events Analyzed by Libertarian Christians