The idea of compiling a Dictionary of commonplaces has been present in Flaubert's mind since 1850. In his letter dated September 4, 1850, to Louis Bouihet, we read the following: “You are right to think about the Dictionary of commonplaces. Completely ready and equipped with a preface, which will supposedly emphasize that it was written to connect the public with tradition, order, established conventions, and structured in such a way that the reader will not realize whether we are mocking him or not, it may be a bizarre work, but also capable of succeeding, because it will be extremely timely.”

The Dictionary, like Bouvar and Pécuchet, with which it is closely linked, is born from the terror as well as the fascination that human folly exercised simultaneously. It gathers material for years, recording ridiculous, foolish phrases and ideas that he hears or reads in the books, newspapers, and magazines of his time, but he would not have time to complete its compilation.

Flaubert's ingenious strategy consists of the simple listing of the monstrosities that are said and written, without any commentary, criticism, or analysis on his part. He believed that mere recording of them would be enough to reveal the magnitude of folly in all its glory. The Dictionary is “an apology for human baseness,” as he notably states, a harsh indictment directed against the bourgeois society of his time, which passively accepts and eagerly adopts all these commonplaces, stereotypes, unexamined ideas, and opinions, an ironic accounting of the limited critical capacity of his contemporaries.