Translated directly from French, “idée fixe” means “fixed idea.” With such a literal translation, it would seem straightforward, but the French term has had multiple applications. Composer Hector Berlioz used it in the early 1800s to describe a recurring theme in his symphonies. Nineteenth-century literary critics used the concept of the “idée fixe” to refer to the obsessive nature of Don Quixote and Captain Ahab, and Arthur Conan Doyle put the phrase in the mouth of Sherlock Holmes directly. But today, “idée fixe” has an almost exclusively psychological connotation to refer to an obsession that dominates an individual’s thoughts.