Inter-disciplinary in Law: Its Necessity & Challenges

– Régis Lanneau

When I started law school, a professor of a certain age was in charge of the welcoming speech. I remember perfectly his words: “Law is a mathematics of language”. An explanation followed on the virtues and the power of the famous legal syllogism, the myth of which persists among bachelor students and certain colleagues; I admit to being impressed by this “demonstration” which seemed to me of an impeccable logic. Law would be a perfectly autonomous discipline. The lawyer should be content to know the “mathematical” rules of law (including cases) while striving to apply them rigorously, penetrated by the wisdom of precedent and academic enlightenment. This vision would be reinforced by a supposed civil law tradition – I am French – making the judge the simple mouth of the law (with his theory on economic development perhaps one of the most beautiful heresy of Montesquieu), the executor of Parliament’s wills (supposed to represent the no less mythical general will). It does not matter that this representation is far removed from the inspirer of the Civil Code-Portalis; it will be enough to read his speech on the civil code to be convinced. It does not matter that the legal tradition does not name the thing – the syllogism – by its name, the modus ponens, and thus reveals that this mode of reasoning is above all one of the logical structures identified by Aristotle. Myths are hard, and believers are faithful to dogmas.

However, the simple fact of giving a history to the notion supposed to have found the autonomy of legal reasoning and thus, of the legal “discipline”, since the disciplines are defined today more by their methods than by their object, suggests that the law is merely, at least, borrowing from logic- one of its tools, thereby putting the idea of a seal between disciplines – or purity of the discipline – at the level of logical impossibility. To be content with an interdisciplinarity limited to logic would however still be far too charitable because, all things considered, legal disciplinesare defined more by their object than by their method. This approach allows both the autonomy of the discipline and interdisciplinarity to be saved. The latter would not in any way affect the autonomy of the discipline (defined as object). Better, it would broaden the scope of legal thinking to make jurists not mere performers but real actors in the evolution of legal norms.

Such an affirmation must, however, be “proven” (improper language if one understands by the proof the mathematical rigor) or at least prove convincing by using a quasi-logical structure and the tools of the traditional rhetoric. This article is itself interdisciplinary in its method, while being legal by its object.

To want autonomy of the discipline as a method does not resist long the analysis of the facts. If, as my former teacher said, law is a mathematics of language, the legal method (what can it be?) should be able to guide judges, lawyers, academics and more generally practitioners to identify, more or less easily but always with certainty, THE legal solution. Indeed, if this solution is not unique, the legal method would not be able to allow a strictly legal decision and it would then be necessary to appeal to an external element which is refused in principle. If we then consider that there are rules imposing the use of another discipline to “decide” between several solutions, these rules do not allow to remove the difficulty: they are indeed legal and if these rules cannot be pinpointed or can be challenged, the problem is only postponed one step further and the autonomy disappears again.

The myth of the unique solution is still widely taught … however, it does not seem logical. After all, the mere fact of using lawyers at a trial to “convince” a judge sufficiently reflects the absurdity of what would be a radical autonomy of law. Do we need three mathematicians to solve a mathematical problem? If the law is a mathematical language, why should we appeal to three entities (two lawyers and one judge)? Isn’t it possible to consider that the “mouth of the law” sufficient? It is indeed necessary here to be charitable, the error of inattention is certainly possible, but it is less frequent than the lawsuits. Lawyers can certainly be stupid and narrow-minded, but then you may wonder why they always find a few things to stay in the business. Would it not be possible to develop software to systematically determine “good” decisions?

Of course, the modus ponens is a structure of presentation that could give the illusion that the solution is “imposed” to the judge when he presents it – our Supreme Courts are experts in this art, which is not always subtle – but we should not confuse effective rhetorical structure with the autonomy of legal reasoning. After all, the field of law is that of the practical decision which is characterized by the fact that things can be other than what they are; mathematical rigor is not entitled to be mentioned in this order; the power of conviction replaces the proof and sometimes claims to be scientific when it is only the ars juris, which is not dishonorable, on the contrary.

Founding myths certainly have their virtues – and the autonomy of law is one – but they should not restrict our ability to think. The cycles and epicycles of Ptolemy were built on the dogma that the perfect movement can only be the circle; the elliptical movement probably does not agree with dogma but has given reasoning an ability to surpass itself. Interdisciplinarity in law is nothing else. The law wanted to think itself as scientific, mimicking mathematical reasoning and, by so doing, ignoring its own nature. It is indeed not interdisciplinarity which is a recent phenomenon, it is the interdisciplinary thought as interdisciplinarity (I). Is this to say, however, that interdisciplinarity must be adorned with all the virtues? As in physics everything depends on what you want to do. The geocentric model is enough to navigate; the model of Newton sufficient to explain many phenomena with some disturbing approximations (the perihelion movement of Mercury for example) but not always crippling; that of Einstein could certainly replace the previous while exceeding them… but remains more complex to handle; it remains the only one that allows the GPS to reach its accuracy. Choosing simplicity is sometimes more efficient for solving the problems of daily life. In other words, the complexity of the theories is not without generating costs (II) that must be taken into account to assess the relevance of a less confidential use of interdisciplinarity (or at least more standard) including, of course, law and economics.

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