Chapter 1 sets the stage for the subsequent chapters by defining and discussing some key terms and situating the thesis of the book within the existing academic literature. It begins by putting forward a critique of one of the most established notions (especially among constitutional law scholars) of democratic transition, a notion mainly based on formal elements (the approval of the constitution), while arguing in favor of the concept of substantive transition, which encompasses elements of “law in action.” The second part of this chapter provides a brief overview of the origins of constitutional justice in Europe, from the Staatsgerichtsbarkeit to the setting up of the first constitutional courts in Czechoslovakia, Austria, and Spain. The analysis then turns to the reasons leading the European constitutional framers – in the period afterWorld War II – to set up constitutional courts, highlighting the fact that the establishment of these bodies is closely linked to the processes of transition to democracy.