Legal Rules: Defeasible or Indefeasible?

The aforementioned proposition is an ascription of the feature of completeness to the rule LR in the context of a given case. The intuition that is behind the concept of the contextual completeness of legal rules is that, in a majority of cases, they are actually viewed as complete in the sense that there is no applicable legal argument that would lead to the conclusion that they are incomplete (in the language of indefeasibilism). If a legal rule is contextually complete in a given context, then there is no possibility of formulating a sound legal argument that would lead to their non-application.

A question arises: when can legal rules be considered contextually complete? The answer to this question is simple and complex at the same time: it depends on the context in which the rule is (re)constructed and applied. The factors that are important for establishing this context are, inter alia, the procedural norms governing a particular type of proceedings (rules of burden of proof, etc.), the active or passive attitude of the parties to the dispute concerning suggestions for answering the questions of law, the constraints stemming from the authority of higher courts, etc. In particular, the presence of controversial moral issues in a given case may raise the contextual standards of the ascription of truth to the contextual completeness statements.

Although it is not possible here to investigate in depth the concept of context that is relevant for establishing the contextual completeness of legal rules, a few comments are in order. The very criteria of identification of factors that are relevant of establishing the elements of this context may be very debatable not only in concrete cases, but also in general. There exist no fixed and uncontroversial theory that would determine the scope of types (and in consequence, of tokens) of these elements. In this connection, it might be claimed that the introduction of the notion of contextual completeness of legal rules simply moves the discussion of defeasibility of legal rules to a meta-level argumentation. This claim would be partially right, but with an important qualification. It may be claimed that if a legal theorist does not intend to assess the existing practice of application of law as generally misled, this practice may be a useful source of information as regards the types (and tokens) of factors that are actually employed for determining that a legal rule in question is contextually complete. What is more, the knowledge concerning this, perhaps to some extent vague, set of factors, will presumably constitute an important part of knowledge of any professional lawyer or judge in any jurisdiction. The topic of factors that are actually relevant for establishing contextual completeness of legal rules should be regarded as an important open question in contemporary legal theory. In our opinion, the topic does not belong to the theory of law itself, but to the theory of legal knowledge (see Guastini 2012, p. 192).

What are the consequences of the adoption of the concept of the contextual completeness of legal rules for the debate between the SDT and its negation in particular and between defeasibilism and indefeasibilism in general? In our opinion, the addition of a contextual completeness statement brings about the following results.

First, the rule-based argumentation scheme may be easily accounted for as a deductive one. This embraces important arguments raised by indefeasibilists. If a disputant argues for the non-application of a rule in question (we assume here that the argument is well formed and that its premises are true), he or she must first show that the rule in question is (contextually) incomplete. However, this does not alter the deductive character of the applied reasoning pattern. In addition, genuine normative conflicts are possible between contextually complete rules. These results give answers to questions raised by Rodriguez (2012) and Ratti (2013).

Second, the concept of contextually complete rules shows that it is possible to circumvent the SDT without adopting infinite, perfect conditional norms (cf. Sartor 1995).

Third, the applied concept of contextual completeness leaves open the question concerning the possibility of the use of novel types of reasons in the legal discourse (as advanced by the SDT). However, it moves this topic to another level of dispute, that is, to the level of elements of context that influence the standards concerning the ascription of the feature of completeness to a legal rule in question.

In summing up the above considerations, an answer to the main question concerning the soundness of the SDT should be formulated. Let us recall that, according to the SDT, a rule is defeasible when its application is contingent not only upon the non-occurrence of events specifiable in advance by particular or type but also by the non-occurrence of conditions specifiable in advance by neither particular nor type. The investigations in this paper lead to a negative answer to this question: the SDT is untenable. However, important intuitions that are encompassed in it should be embraced at another level of legal discourse: the level concerning the contextual completeness of legal rules.


This paper argues for a middle ground in the dispute between legal defeasibilism and indefeasibilism. The concept of the contextual completeness of legal rules was introduced to supply a traditional rule-based argument scheme to obtain two results: preservation of the deductive character of legal rule-based reasoning and embracing the openness and contextual sensitivity of legal discourse as advanced by the strong defeasibility thesis. The paper’s original import was preceded by a detailed review of the discussion of the concept of the defeasibility of legal rules in the literature of the subject. In particular, rules of translation were formulated concerning the account of certain problems in the application of law from the point of view of defeasibilism and indefeasibilism.

The concept of contextual completeness is obviously a controversial proposal, in part because it is based on the basic ideas of a contestable epistemological theory: epistemic contextualism. As for perspectives of further research on this issue, the elements of legal context that are relevant for the ascription of the feature of relative completeness to legal rules should be scrupulously investigated.


The author thanks Jaap Hage, Giovanni Battista Ratti, and Andrej Kristan for their valuable comments in connection with the presentation of this paper during the RULES 2013 (September 27–29) conference in Kraków.


Alexy, Robert. 1989. A theory of legal argumentation

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