Impurities in Kelsen’s Pure Theory

Kelsen’s theory claims be precise and concrete, and to separate law from other concerns such as morality and sociology. I think that there are at least two ‘fudge factors’ that are imprecise, and allow these other disciplines to bleed back into the theory.


1) Effectiveness

According to Kelsen, all legal norms are either valid or invalid, and one of the conditions for validity is that the legal norm be ‘by and large effective.’ You need to take a middle path in terms of effectiveness: effectiveness must be taken into account, so that you don’t get absurd legal systems, but you also don’t need all the laws to be effective all of the time.

You definitely need effectiveness, because otherwise any hypothetical system of coercive norms can be law, and the legal scientist has to arbitrarily choose the ‘correct one.’ But effectiveness has problems.

Effectiveness is both imprecise and impure (in terms of the Pure theory). Kelsen does not explain how to determine whether a norm is effective, and such a process would need to answer various non-legal questions, such as:

  • Are some laws more ‘serious’ than others, i.e. is it more important that the law of murder be obeyed than the law of theft?
  • If we want to determine whether the law against speeding is effective with respect to a particular citizen, do we need to take into account how often she drives? What about her moral attitude towards speeding?
  • Effectiveness lies on a spectrum – where do we draw the line?

Effectiveness is looking like a necessary impurity in Kelsen’s theory.

This is also a problem in science: the various scientific disciplines describe one reality, but use different methodology. So they often make assumptions that seal each other off from each other – physics assumes lots of simplifying mathematical properties that might not be well defined, and biology assumes lots of physical properties that might not be well defined. This is a ‘flaw,’ but a flaw with practical benefits, because you get useful answers. People acknowledge, when they make such assumptions, that their model/theory will be no good if the assumptions turn out to be false.

In terms of Kelsen, maybe you could argue that the only way to make effectiveness precise would be to compromise the Pure Theory and bring in all the sociological and moral considerations. By refusing to elaborate on ‘by and large effective,’ Kelsen could be sealing off those considerations and keeping the theory Pure.

To seal off questions about effectiveness, you would need to make an assumption like ‘it is always clear whether a law is by and large effective’. In situations where effectiveness is not clear, such as when a society is unstable, Kelsen would have to concede that his theory had major problems.


2) Interpretation

A legal scientist can describe the possible interpretations of a legal norm, but only an authorised legal organ can choose which interpretation to actually implement. However, if a legal organ chooses an interpretation that the scientist thought was ‘impossible’, the scientist may not consider the resulting norm to be valid.  Legal interpretation can therefore affect the content of the Pure theory.

The theory definitely needs to allow legal scientists to interpret norms. Otherwise, a legal norm would be meaningless to a legal scientist, and they could only understand it by looking at its effects. However, legal interpretation uses things like ‘purpose’ that are beyond legal science. So these other disciplines have another way to bleed into the pure theory.

Kelsen sets a low standard here though: the scientist doesn’t need to choose the correct interpretation, they just need to identify all the ‘possible’ interpretations. This gives us an assumption that ‘seals off’ the politics of interpretation from the pure theory: it will always be clear whether an interpretation is possible.

You can easily think of hypothetical scenarios where this assumption is no good, for example, if a judge tries to prosecute a murderer with a law ‘Thieves should be punished,’ on the grounds that the murderer ‘stole’ life. I think it is not clear whether this interpretation is ‘possible.’ But in reality, such situations seem implausible, which makes the assumption seem pretty good. Kelsen would still have to admit there are some situations (such as a corrupt judge abusing their power) where this assumption could cause problems.


 Kelsen’s desire for rigour and precision is risky because the theory might begin to deviate from a reasonable understanding of law. The two fudge factors, effectiveness and interpretation, work well to keep Kelsen’s theory grounded in reality, but they also compromise its purity. If the questions ‘is this law effective?’ or ‘is this a possible interpretation?’ are difficult questions, then the Pure theory does not have the right machinery to analyse the law. I think this is therefore a flaw in the theory, though I don’t see an easy way of solving it.

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