"With regard to the other element in punishment, its fluid element, its meaning, the idea of punishment in a very late stage of civilisation (for instance, contemporary Europe) is not content with manifesting merely one meaning, but manifests a whole synthesis "of meanings." The past general history of punishment, the history of its employment for the most diverse ends, crystallises eventually into a kind of unity, which is difficult to analyse into its parts, and which, it is necessary to emphasise, absolutely defies definition. (It is nowadays impossible to say definitely the precise reason for punishment: all ideas, in which a whole process is promiscuously comprehended, elude definition; it is only that which has no history, which can be defined.)"
— From The Genealogy of Morals, Second Essay, Section 13.
(Hat tip to John Budd for bringing this quote to my attention.)