Let’s do an experiment. Try to remember what was going through your mind right before you began reading. Concentrate on whether your thoughts had the quality of spoken words. If so, what were they saying? Were they dithering over a work email? Shouting out a preference for dinner? I’ve made it difficult for you, of course, because now you’ve had to summon a new voice in order to read. But before you began reading, there might have been another voice coursing freely through your mind.

Inner speech seems to be an essential part of our experience. It pays court to our memories, deciphering our conscience and our desires. It murmurs and chants in the most elemental corridors of our minds. It may be rooted in the avid listening we did as children, an internalization of the conversation...