This introductory chapter assesses whether there is a European constitution. When examined in the light of the broader historical tradition, the European Union has a constitution. And this view firmly corresponds to the self-understanding of the European legal order. The ‘real’ problem of the European Union is not whether there is a European constitution, but rather that there is ‘too much constitutional law’; the European Treaties alone contain 413 articles. Length is unfortunately not the only problem of the European constitution, for unlike more mature legal orders, the European constitutional order still struggles with its ‘vocabulary’. The semantic confusions are partly the result of the constant legal revolutions within the European Union. This book then aims to reflect the judicial and legislative practice of the Union as at October 31, 2020. It provides a guide through the most important theories and realities of the European Union law.