Language furnishes the best ...

Language furnishes the best proof that a law accepted by a community is a thing that is tolerated and not a rule to which all freely consent.
 Ferdinand de Saussure

Quotes from the same author

It is useful to the historian, among others, to be able to see the commonest forms of different phenomena, whether phonetic, morphological or other, and how language lives, carries on and changes over time.
 Ferdinand de Saussure
In general, the philological movement opened up countless sources relevant to linguistic issues, treating them in quite a different spirit from traditional grammar; for instance, the study of inscriptions and their language. But not yet in the spirit of linguistics.
 Ferdinand de Saussure