This book is the result of the teaching we provide to second-year law students in the introductory course on scientific research and legal methodology. It is addressed in particular to researchers in Law in the interdisciplinary sphere, it teaches the recipients how to proceed with method when it is a question of doing a research or to solve a specific problem in Law, the interpretation of a legal rule... the work wants to be at the same time a mirror of its practices and an invitation to rally to those of them which, either appear dominant, or bénéficient of the most convincing arguments. There remain, of course, a significant number of cases in which one must choose. The main merit and is it not decisive for a jurist? Of the selection proposed by the authors is that it has been collegially decided, after mature discussion. If one does not agree with it, while remaining convinced of the need to unite practices, it remains to engage with the authors in the dialogue to which they do not fail to invite their readers. This will also be a way of recognizing the value of their undertaking.