The Languages of Pao is a science fiction novel by Jack Vance, first published in 1958, in which the Sapir–Whorf hypothesis is a central theme.
The planet Pao is a quiet backwater with a large, homogeneous, stolid population ruled by an absolute monarch: the Panarch. The current Panarch attempts to hire an offworld scientist, Lord Palafox from the Breakness Institute on the planet Breakness as a consultant in order to reform Pao. Before the deal can be concluded, however, the Panarch is assassinated by his brother Bustamonte, using mind-control over the Panarch's own son, Beran Panasper, to do so. Lord Palafox saves Beran Panasper and takes him to Breakness as a possible bargaining chip in his dealings with Pao.
Somewhat later, Pao is conquered by the Brumbo Clan from the planet Batmarsh and the Panarch Bustamonte is forced to pay heavy tribute. To rid himself of the Brumbos, he seeks the aid of Palafox, who has a plan to create warrior, technical and mercantile castes on Pao using customized languages and other means to shape the mindsets of each caste and to isolate them from each other and the general populace of Pao. To achieve this, each caste gets a special training area where it is completely segregated from any outside influence; the necessary land is confiscated from families, some of which had held it for countless generations—which creates some disaffection in the conservative Paonese population and earns Bustamonte the name of a tyrant.
In order to return with them to Pao incognito Beran Panasper infiltrates a corps of interpreters being trained on Breakness. Mostly to amuse themselves, some of the young people create a language they call "Pastiche", taking words and grammar from the three newly created languages, Valiant, Technicant and Cogitant, and from the original Paonese language and mixing them seemingly at random. Palafox looks upon this development with indulgency, failing to realize the tremendous long-term significance.
Beran returns to Pao under the name Ercolo Paraio and works for a few years as a translator at several locations. Once Beran Panasper reveals to the masses that he is still alive, his uncle Bustamonte's popular support melts virtually overnight and Panasper claims the title of Panarch that is rightfully his. The Brumbo Clan is repulsed by the warrior caste. For a few years, the castes of Pao are highly successful in their respective endeavors and the planet experiences a short golden age. However, Panasper is upset about the divisions in the populace of Pao caused by the Palafox program; the three new castes speak of the rest of the Paonese as "they" rather than "we" and regard them with contempt.
Beran attempts to return the planet to its previous state by re-integrating the castes into the general populace. Palafox opposes this move and is killed, but the warrior caste stages a coup and takes command of Pao. Panasper convinces them that they cannot rule the planet alone, since they share no common language with the rest of the population and can not rely on the cooperation of the other segments of the people of Pao, and they allow him to keep his office.
One interpretation of the end of the novel is that Beran Panasper is only in nominal charge of the planet, on the sufferance of the warrior caste, and that it is uncertain what will become of him and his plans of re-uniting the populace of Pao. Another way of seeing the ending is that Beran has outfoxed the warriors by getting them to agree to his decree that "every child of Pao, of whatever caste, must learn Pastiche even in preference to the language of his father". In the end, Beran looks ahead twenty years, to a future when all inhabitants of Pao will be Pastiche-speakers — i.e., will speak a language which mixes some attributes and mindsets appropriate to peasant cultivators, proud warriors, skilled technicians and smart merchants — which will presumably shape a highly fluid and socially-mobile society, composed of versatile and multi-skilled individuals.
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