Pufendorf: On the Duty of Man and Citizen according to Natural Law

1. Everyone knows how useful, how simply necessary, an instrument of human society language [sermo] is. Indeed, it has often been argued, on the basis of this faculty alone, that man is intended by nature to live a social life. The legitimate and profitable use of language for human society is based upon this duty prescribed by natural law: no man should deceive another by language or by other signs which have been established to express the sense of his mind [sensa animi].

2. A more profound grasp of the nature of language requires a knowledge of the double Obligation incurred by using it whether in Speech or in writing. The first is that users of any given language [lingua] must employ the same words for the same objects following the usage of that language. For since neither sounds nor particular letter-shapes naturally signify anything (for if they did, all languages or forms of writing would necessarily converge), the use of a language would become meaningless if everyone could give an object any name he wanted. To prevent this, it is necessary for a tacit agreement to be made among users of the same language to denote each thing with one particular word and not another. For without an accord on the consistent employment of sounds, it is impossible to understand from what someone says the sense of his mind. By virtue of this agreement everyone is obliged to use words in his common discourse in the sense they bear in the accepted usage of that language. It follows from this too that, although the sense of a man's mind may be at variance with what he says, yet in the afFairs of human life everyone is assumed to have meant what his words indicate, even if it deviates perhaps from the inner intention of his mind. For we can know nothing of his mind except by signs; and therefore all use of language would be rendered futile if an internal mental reservation, which each man can form as he pleases, could undermine the usual force of signs in social life.