A language is not simply a collection of phonetic signs. It is an instrument of thinking and acting. Its vocabulary and grammar are adjusted to the mentality of the individuals whom it serves. A living language spoken, written, and read by living men—changes continually in conformity with changes occurring in the minds of those who use it. A language fallen into desuetude is dead because it no longer changes. It mirrors the mentality of people long since passed away. It is useless to the people of another age no matter whether these people are biologically the scions of those who once used it or merely believe themselves to be their descendants. The trouble is not with the terms signifying tangible things. Such terms could be supplemented by neologisms. It is the abstract terms that provide insoluble problems. The precipitate of a people's ideological controversies, of their ideas concerning issues of pure knowledge and religion, legal institutions, political organization, and economic activities, these terms reflect all the vicissitudes of their history. In learning the meaning the rising generation is initiated into the mental environment in which they have to live and to work. This meaning of the various words is in continual flux in response to changes in ideas and conditions.
Teoría e Historia, cap. 10, punto 6.