This is the twelfth book in the series The Common Core of European Private Law published within the Cambridge Studies in International and Comparative Law . The project was launched in 1993 under the auspices of the late Professor Rudolf B. Schlesinger. The methodology used in the project is still unparalleled. By making use of case studies it goes beyond mere description to detailed inquiry into how most European Union legal systems resolve specifi c legal questions in practice, and to thorough comparison between those systems. It is our hope that these volumes will provide scholars with a valuable tool for research in comparative law and in their own national legal systems. The collection of materials that the Common Core Project is offering to the scholarly community is already quite extensive and will become even more so when more volumes are published. The availability of materials attempting a genuine analysis of how things are is, in our opinion, a prerequisite for a fully-fl edged and critical discussion on how they should be. Perhaps in the future European private law will be authoritatively restated or even codifi ed. The analytical work carried on today by the almost 200 scholars involved in the Common Core Project is a precious asset of knowledge and legitimisation for any such normative enterprise.