A common European private law does not simply exist uniquely through community law and international conventions, but also through the similarity of principles to be found in national legal Systems. These common legal principles form the basis for a creative interpretation of Community law by the European Court of Justice. Moreover they make it possible for lawyers of different European legal Systems to corne to an understanding in spite of the differences of rules, Systems and casuistry of their national law. On this basis, it is also possible to extend the conventional methods of interpretation. A comparative or harmonious approach to interpretation, aimed at bringing national private laws doser to each other and to the European Community avoids immanent interpretation of national laws. This essay deals with one discussion of this question in Germany, and seeks to contribute to an exchange of views between lawyers from different legal Systems in Europe on the common methodical and historical foundations of European private law, and on the « Europeanisation » of the doctrine of private law.