Combining Finnis with Kelsen

I have looked at two theories that define legal law, (1) the theory of Hans Kelsen, who argues that law is completely separate from morality, and (2) the theory of John Finnis, who argues that law is completely tied up in morality.

I think the two theories aren’t actually that hard to reconcile to form a big Finnis-Kelsen theory.


Kelsen’s theory creates a discipline legal science, which deals only with questions of law. Kelsen acknowledges that a judge/legislator/whoever will make decisions that deal with non-legal factors, but he excludes such factors from legal science. While Kelsen himself argues that there are no objective morals, his theory would still work if such morals did exist because the Pure Theory of Law exists only within legal science, and morals exist outside of legal science.

Meanwhile, Finnis proposes objective, basic goods that every human wants to participate in. The best way to do this is to coordinate as a society, and a very good way to coordinate is through law. However, Finnis grants that any decision that there are many equally valid moral decisions – any decision made in accordance with the seven basic goods and the nine requirements of practical reason is a morally acceptable decision. Therefore there are many ways to construct a legal system.

Additionally, Finnis distinguishes between legal validity (which is within legal science) and moral validity (beyond legal science). You can implement a legal system that does not fulfil the basic goods, and such a system will have legal validity, but not moral validity.

It seems to me that these theories are not actually opposing. Instead they slide by each other, dealing with different subject matter, and so we can put them together.
Finnis’s theory tells us how the law should be, while Kelsen’s tells us how it actually is. We can examine a particular law and asks questions of legal science, such as ‘is this law legally valid?’ or we can ask moral questions like ‘is this law morally valid?’ Since legal science is separate from morality, the two theories will not contradict, and any legal question that we ask will be answered by exactly one theory.

We can look at a society, and we can differentiate between that society’s underlying moral rules and its positively created legal rules. We can examine the first system using Finnis, and the second system using Kelsen. This allows us to answer questions like “How good is this legal system?” because we have precise definitions of (1) the legal system and (2) what it means to be good.

The one area of overlap is decision making – what factors will a judge (or some other legal organ) take into account when they make a legal decision? Such a decision takes into account both moral and legal considerations. However, both theories are incomplete in describing this legal process – Kelsen says that it is beyond legal science, while Finnis says that as long as you obey practical reason, you can do whatever you want. Neither theory explains or prescribes the thinking process of such a legal organ, so there is no contradiction here. You could admit however, that the Finnis-Kelsen theory is therefore not a comprehensive theory of law, and if that was what you wanted, you’d need to add even more stuff to it.


In the Pure Theory of Law, Kelsen argues that natural law is both wrong and incoherent, and so he would probably not be happy with a Finnis-Kelsen theory. However, as I have said, the Pure Theory does not fail if we allow the existence of natural law.

Kelsen’s specific arguments against natural law are not very effective against Finnis’s theory:

Kelsen first argues that natural law must be wrong, because there are no objective moral standards. He says that this is clear because no common morals can be found between societies. Finnis’s theory of basic goods expressly deals with this argument; his reply can be summarised as ‘Yeah, but people who don’t believe in the basic goods are wrong.’ More details can be found in my summary posts on Finnis.

Kelsen also argues that natural law is incoherent – any system of law is founded on a Grundnorm, which is arbitrarily chosen no matter what.
We can deal with this argument too. Firstly, natural law is distinctly different to positive law, and exists outside of legal science. Therefore it does not require a Grundnorm. However, natural law does need ‘moral validity,’ and the source of this validity must come from some moral form of a Grundnorm.  But the decision of which Grundnorm to adopt is not arbitrary – it must reflect the law that is actually followed. If we want to choose a moral Grundnorm that grants moral validity, it must reflect the morals that actually exist. Therefore the choice of moral Grundnorm is not arbitrary.

Therefore Kelsen’s arguments for moral relativism do not do well against Finnis’s theory, but this does not mean that the Pure Theory itself is weakened. Once Kelsen’s theory makes this concession, I think that it fits quite well with Finnis’ theory to create a Finnis-Kelsen theory that describes natural and positive law, and can discern relationships between the two.


I have spent this week learning about Finnis’ theory, and have not yet made a proper effort to compare natural law with scientific law. However, once we put Finnis and Kelsen together, I think we can formally justify a neat parallel:

The natural world is confusing and uncertain. We try to construct scientific theories that are logical and precise, which approximate the natural world. We have to make trade-offs between the logical completeness of the theory, and the theory’s ability to accurately describe nature. In the same way, the natural law is confusing and uncertain. We construct systems of positive law that are logical and precise, which approximate the natural law. We have to make trade-offs between the logical completeness of a legal system, and the legal system’s ability to accurately replicate the natural law.

I thought of this parallel during my introductory law courses at the start of 2014, and I don’t think it’s very insightful on its own. However, once you look at it in the context of the Finnis-Kelsen theory, it becomes a lot more precise and interesting. This is the kind of thing I want to look into in the last two weeks of the project.

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2 Responses to Combining Finnis with Kelsen

  1. Luís Guilherme Netto Andrade says:

    Dear Mr. McCarthy,

    I am writing because I have readen this article and I found it a great material to use. I am a lawyer from Brazil, and I’m researching material of natural law (more precisally John Finnis) for my own knowledgment and academic interest. Additionally, I would like to ask your permission to translate this article, and use it (make references to you) to write an article here in Brazil about it.

    If you have any questions, please don’t hesitate to contact me.

    Best regards,

    Luís Guilherme Netto Andrade


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