Law of obligations is the most universal and timeless branch of civil law. Alongside with the commercial law it was the ﬁrst to be uniﬁed whenever harmonization of a private law occurred: during the 19th century in the United States, in Germany and in the Swiss Confederation as well as during the 20th century in the Nordic countries or in Poland. If uniﬁcation of the law of obligations in the European Union fails, chances for other branches of civil law will be even smaller. A European Code of Obligations, may be only as „optional instrument”, must fulﬁll the same subsidiary function in relation to national laws as the old ius commune did in relation to the local iura propria. However, the ius commune was completed only around 1400, i.e. three centuries after rediscovery of Justinian’s Digest. Glossators and commentators of today cannot accomplish a similar task within three decades.