1 THE ITALIAN LAW JOURNAL NO. 2 (2015) Structured Error. Case Study on a Discourse Logic of Comparative Law by Bertram Lomfeld Taking legal reactions on errors in contract formation (the ‘law of errors’) as a paradigm, this case study outlines the method of a ‘discursive comparative law’. Following a critical view on the prevailing methods of comparative law (I), the essay explores the idea of ‘deliberative comparisons’ between legal cultures (II). A ‘discourse logic’ compares structures of legal argumentation in different jurisdictions and reveals its competing ethical and political reasons. From that perspective, contract law turns into a political battlefield of normative legal principles (III). A comparative discursive analysis of the ‘law of errors’ in Germany, France, Italy and England, however, shows amazingly similar argumentative structures (IV). A second stunning result is the discursive picture of European private law. The unifying European Common Frame of Reference pluralizes the field of normative reasons (V). Here, to structurally demonize legal harmonization per se would be in itself a ‘structured error’.