There is nothing more powerful than an idea whose time has come.

Often attributed to Hugo as a paraphrase of a similar idea in his Histore d'un Crime (1877): "One resists the invasion of armies; one does not resist the invasion of ideas", the wording of this famous statement actually more closely resembles a passage from the relatively obscure Les Francs-Tireurs (1861) by Gustave Aimard, p. 68

Il y a quelque chose de plus puissant que la force brutale des baïonnettes: c'est l'idée dont le temps est venu et l'heure est sonnée. | There is something more powerful than the brute force of bayonets: it is the idea whose time has come and hour struck. | Translated into English as The Freebooters : A Story of the Texan War (1861), p. 57, Ward & Lock edition