"The EU legal order sits above a diverse mix of 27 national legal systems, with some 23 different languages. Amongst such diversity, how can the unity and coherence of the European legal system be guaranteed? Is there a common understanding between lawyers from different national backgrounds as to the meaning and application of EU law? In addressing these issues the idea of ‘common concepts’ has played a crucial role. It is argued that the unity of the system is guaranteed by the consistent application of certain core principles shaping the law. " (Quoted from page)