The modern idea of a written constitution dates from the end of the eighteenth century. 1 This development has brought with it the almost inevitable question: what is a constitution? The posing of this question amounts to a search for the essence of a constitution in general, or for the essence of a particular constitution. The importance of the ‘what is’ question lies in the fact that the essence so found has a number of important implications, inter alia in relation to the question as to the continued existence of constituent power after its exercise (Chapter 3), the relation of the constitution to the state, that is, whether transnational constitutions or an international constitution is possible (Chapter 7), constitutional interpretation, the question of sovereignty (Chapter 3) and the limits or restrictions imposed in relation to constitutional amendments (CT 140–66). In constitutional theory one would usually speak in this respect of the ‘concept of the constitution’, and various such ‘concepts’ have been explored.