Justin E. H. Smith in Aeon:
As the theorist Walter J Ong pointed out in Orality and Literacy: Technologizing the Word (1982), it is difficult, perhaps even impossible, now to imagine how differently language would have been experienced in a culture of ‘primary orality’. There would be nowhere to ‘look up a word’, no authoritative source telling us the shape the word ‘actually’ takes. There would be no way to affirm the word’s existence at all except by speaking it – and this necessary condition of survival is important for understanding the relatively repetitive nature of epic poetry. Say it over and over again, or it will slip away. In the absence of fixed, textual anchors for words, there would be a sharp sense that language is charged with power, almost magic: the idea that words, when spoken, can bring about new states of affairs in the world. They do not so much describe, as invoke.
As a consequence of the development of writing, first in the ancient Near East and soon after in Greece, old habits of thought began to die out, and certain other, previously latent, mental faculties began to express themselves. Words were now anchored and, though spellings could change from one generation to another, or one region to another, there were now physical traces that endured, which could be transmitted, consulted and pointed to in settling questions about the use or authority of spoken language.
Writing rapidly turned customs into laws, agreements into contracts, genealogical lore into history.