Ordinary language is, literally at every moment, subject to mutation. This takes many forms. New words enter as old words lapse. Grammatical conventions are changed under pressure of idiomatic use or by cultural ordinance. The spectrum of permissible expression as against that which is taboo shifts perpetually. At a deeper level, the relative dimensions and intensities of the spoken and the unspoken alter. This is an absolutely central but little-understood topic. Different civilizations, different epochs do not necessarily produce the same ‘speech mass’; certain cultures speak less than others; some modes of sensibility prize taciturnity and elision, others reward prolixity and semantic ornamentation. Inward discourse has its complex, probably unrecapturable history: both in amount and significant content, the divisions between what we say to ourselves and what we communicate to others have not been the same in all cultures or stages of linguistic development.
– George Steiner, After Babel: Aspects of Language and Translation (1975)