Spoilers for Snow Crash follow.

Snow Crash posits that there is a natural language for human brains, akin to assembly code, and that the line between pre-historic and historic humanity comes from a singular event. That natural language is/was (pre)Sumerian, and well-formed sentences in that language are indistinguishable from internal thoughts: to speak is to command belief, to hear is to believe. The singular event is the nam-shub of Enki (http://namshub.com/enki.html) which established a virally propagating firewall that cut off the ability to understand pre-Sumerian and allowed/forced the development of other languages, none of which had the interiority of pre-Sumerian.

This is all codswallop, but it's entertaining.

I'd highly recommend Embassytown. The interpreter has to deal with a species that has two heads that communicate seemingly independently - bicameral mind indeed!