Transactions concerning commercial parties, for example the so-called ‘b2b’-contracts, are often dealt with by specific rules. But to what extent are these exceptions from general private law actually justified, and where should they have their place within a codified system? Civil law countries have traditionally assembled matters of commercial law in a commercial code; in some cases, such as Germany or Spain, the commercial code was enacted even before the civil code. However, since the beginning of the 20th century, a growing number of legal systems (e.g. Switzerland or Italy) have decided to put an end to this dichotomy and to deal with the whole of private law in just one body of law. The aim of this paper is to show that our perception of commercial law and its legislative treatment are often shaped by historical contingencies. To be aware of these is not only important in the national context, but also in the process of European or even worldwide harmonisation of contract law.