The Primacy of Spoken Language
The idea that speech is the original and primal form of language, and writing a secondary imitation of speech, runs counter to the general popular accordance of greater prestige to writing. Yet the primacy of spoken overbecame embedded in in the early 19th century, doubtless in connection with the Romantic belief that embodied the national spirit more deeply than urban practices like writing, which were more subject to extreme influences.
The trend continued over the course of the 19th century as Linguistics moved away from philology and became increasingly concerned with the gathering of spoken forms from living dialects. By the turn of the 20th century few linguists would have disputed that the best source for determining the original form of anything in any language was to reconstruct it from its living descendant dialects, and not from written records surviving from intermediate stages.