Building on the theoretical insights of Kelsen, Hart and Ross, the paper agrees that there are neutral (or formal) criteria for identifying legal systems and for distinguishing these systems from other forms of normativity; which leads us to support the arguments developed by Brian Tamanaha and Baudouin Dupret against pluralist theories which find ‘law’ in all manner of social regulations. By contrast, the question of how to define the state has proved to be much more controversial. As is well known, in attempting this task, the jurist runs the risk of choosing a definition which is inadequate, in that it fails to take into account all the historical situations. Equally, the definition chosen may be too narrow, if it is created with the specific goal of accounting for a determined situation. To overcome these problems, we propose to combine the approaches of a legal historian (Jean-Louis Halpérin in the first part) with those of a legal theoretician (Pierre Brunet in the second part). They can be combined, as the first one focuses on the characterisation of the legal order and the second one on the set of doctrines that has conceptualised the state.