Only some of us hear it. Some of you have a running monologue, words narrating the self all day. Others think in feeling, in image, in something that has no name yet. But if the format of thought is this different from person to person, what does that say about its source? Are we characters inside an observing world? And if so, do we even own our thoughts, or are we just the last ones to hear them, mistaking the echo for the voice? Who is the author, if there is one? Would they even know the...