Momentary and Non-momentary Legal Systems

Raz made a fundamental step forward in the theoretical reconstruction of legal dynamics when he introduced the distinction between momentary and non-momentary legal systems. The former concept refers to all those norms that are valid at a particular time; the latter is a broader concept that refers to something like the legal history of a particular community. The distinction between momentary and non-momentary legal systems is designed to shed light on the interplay between the changing content of law and its continuity over time, because it helps us to understand the reason why a pair of norms which were valid at different times can be regarded as members of the same municipal law even if they never belonged to the same momentary system. Non-momentary legal systems – also called “legal systems” simpliciter by Raz – show how the legal history of a political community is mainly developed by means of the introduction and elimination of valid norms. In non-momentary legal systems, genetic relations play a fundamental role because they define normative hierarchies and conditions for exercising normative powers. For this reason, Raz stresses that in every legal system there are genetic relations between norms.

In the creation of norms, there is a genetic relation between a power-conferring norm and the new norms created by the exercise of such power. The relevance of such relations among norms seems to be obvious: unlike morality, law often changes by specific normative acts performed by legal authorities. In fact, a person (or organ) is a legal authority only to the extent that she is allowed to modify the deontic status of certain actions. Thus, authority and creation of norms are conceptually related, and any explanation of the nature of law would be defective if this characteristic of legal systems were not taken into consideration.

Throughout this book, we have attempted to show some of the possibilities that logical analysis offers for the study of legal systems. To do so, we have presented an introduction to the basic aspects of deontic logic and contrasted the attitudes of optimism and skepticism about the possibility of accepting logical relationships among norms. In the first chapters, we briefly reviewed the connections between propositional logic, predicate calculus, alethic modal logic, and deontic logic, and then offered a schematic outline of the different systems of deontic logic that constitute the conceptual basis that has generated the most important technical developments in deontic logic. Unlike philosophers who regard norms as a special type of propositions, we have emphasized the pragmatic aspects that characterize directive discourse, and defended the idea that the most promising way to justify the existence of a logic of norms is on the basis of an abstract notion of logical consequence, which allows the development of a genuine logic of norms without making the controversial assumption that norms have truth-values.

Paradoxes of Deontic Logic

Almost since its origins, deontic logic has been threatened by several paradoxes, elaborated by theorists to highlight different shortcomings that seem to derive from its fundamental axioms. The discovery of such paradoxes led some deontic logicians toward an attitude of general skepticism about the discipline, for as Rescher remarked, “it is…only fair to say that there is virtually no issue in the field upon which a settled consensus has been reached.”

However, no area of logic is free from paradoxes. One of the main impulses at the beginnings of alethic modal logic was a certain sort of discomfort with material implication – for example, the rather counterintuitive consequence that stems from tautologies such as (p→q) ∨ (q→p). But these new developments in modal logic did not generate a skeptical attitude toward it; instead, they were regarded as opportunities for clarifying the properties of logic itself. And in fact, the same goes for deontic logic: from a technical point of view, paradoxes provided a decisive impetus toward sharpening the basic concepts of deontic logic. Thus, even if some of these paradoxes expose serious obstacles for deontic systems, their discussion, as much as the answers that have been offered for each of them, made a significant contribution to the progress of this area of logic. As Russell rightly noticed, paradoxes and puzzles play a crucial role in testing a logical theory.

Normative Systems and the Existence of Norms

In the preceding chapter we pointed out the importance of distinguishing norms from norm-propositions. Although there are notable difficulties regarding the possibility of a genuine logic of norms, it is relatively uncontroversial that logic can be applied to norm-propositions, understood as propositions about the membership of a certain norm in a normative system. Concerning this last question, the problems are not so much about the very possibility of applying logic to norm-propositions, but rather about whether the logic of norm-propositions is something different from a genuine logic of norms, or whether the logic of norm-propositions is a special kind of logic or, by contrast, is no more than a fragment of classical logic.

One way to show the relevance of the logic of norm-propositions as something different from a logic of norms is through the analysis of the logical consequences of normative systems, particularly their logical properties, such as coherence and completeness. In what follows, we apply this analysis to a particular kind of normative systems: legal systems.

In The Critique of Pure Reason, Kant claims that from the time of Aristotle until his time, logic had been “unable to take a single step forward, and therefore seems to all appearance to be finished and complete.” Moreover, he adds that some alleged improvements were only minor changes or, even worse, confusing and full of misunderstandings. But contrary to this vision, the last two centuries have witnessed an extraordinary rebirth of logic. New approaches to classical problems, as well as new horizons opened to logical exploration (e.g., modal logic, the logic of relevance, the logic of action), have gained a legitimate reputation in contemporary philosophy.

One of these new logical domains is deontic logic, the branch of logic that offers a formal analysis of normative discourse. Law is one of the most important normative fields, and deontic logic constitutes an invaluable aid for legal scholars and philosophers in the analysis of fundamental legal concepts. More specifically – as we try to show – deontic logic can be regarded as an essential tool to understand both the systematic structure of law and its dynamic nature. Undoubtedly, deontic logic is also useful for the evaluation of moral discourse, but in this book we limit our attention to the legal domain, with very few and merely incidental remarks on morality.

Logic of Norms and Logic of Norm-propositions

So far we have been dealing with the problem of the foundations of deontic logic, particularly with the controversial relation between propositions and norms. And although the thesis that norms are proposition-like entities is highly controversial (we have, in fact, rejected that point of view), there is no disputing the propositional character of the discourse about norms. It is unreasonable to deny the possibility of formulating true or false descriptive statements about the norms that belong to a certain normative system.

The difference between genuine norms and statements about norms is quite apparent. However, as previously noticed, the problem is that the very same words (e.g., “Parking is not allowed here”) may be used, depending on the context, either to formulate a norm (when the speaker is a norm-authority) or to express a norm-proposition (about the norms issued by a certain authority). Perhaps this ambiguity helps to explain the unfortunate reason why, although the distinction with different names has been noticed by several authors, it has received little attention in the analysis of the logic of normative discourse.

Validity, Truth, and Logical Form

An argument can be defined as a set of statements of a given language in which the truth of one of them (the conclusion) is assured by the truth of the others (the premises). Logic has to do with the study of arguments, but it is not a discipline oriented to describe our actual practices of argumentation and reasoning. It does not purport to examine the actual psychological processes or states of mind of people. In particular, it is not an empirical task whose outcome varies with different universes of analysis (i.e., different human groups and times). Instead, logic is concerned with a critical evaluation of argumentation; with patterns of correct reasoning.

However, this is still inaccurate as a proper characterization of logic, because any critical assessment of argumentation depends on the implicit goals ascribed to it, and there is not one but a plurality of goals we may seek to accomplish in our argumentative practices. For example, if we intend to persuade an audience, arguments will be evaluated as good or bad according to their merits to the extent that the audience is actually persuaded by our words. That would be an example of a rhetorical assessment of argumentation.