This contribution explores the leading principle in the comparative method of law: functionality of comparisons. The principle is defined, conditioned and analysed. In particular, the author wishes to maintain with this article the orthodox approach when it comes to understanding the principle of functionality for the comparative method. The article’s analysis proceeds with an examination of whether functionality is concerned with similarities and/or differences. The author suggests that it is possible that functionality can operate for the identification of differences and the identification of similarities, the stress being on the latter. The article then argues that functionality serves as a common, unifying and mutually intelligible den...