Do you remember the last time you were talking to someone for more than a couple minutes? Maybe they were explaining something to you, or telling you a story. You might try to remember what they said later - you can’t hear it, but your brain kind of recreates the sensation of having been spoken to even though your ears aren’t receiving those sounds.

That’s what having an inner voice is like (to me, anyway) - it’s remembering a conversation that you never actually had.