Although harmonisation has been a topic of debate in the EU since its creation, and despite the abundance of academic publications on the topic over the years, there remains a lack of conceptual framework or overarching theory of harmonisation. This is problematic because the EU is an inherently complex machinery, whose functioning can be difficult to grasp for lay audiences. Undefined concepts lead to misconceptions which exacerbate the communication gap between 'Brussels' and its Member States. The lack of definitions of core principles and concepts of EU law, such as the word 'harmonisation' explains this poor understanding of the law-making process because it allows the word to be used at cross-purpose. The objective of the book is to debunk the idea that EU harmonisation measures are made in 'Brussels' behind closed doors and imposed top-down on the Member States. The book promotes the vision of the EU as an arena of dialectic law-making.