We all hear voices. Ordinary thinking is often a kind of conversation, filling our heads with speech: the voices of reason, of memory, of self-encouragement and rebuke, the inner dialogue that helps us with tough decisions or complicated problems. For others - voice-hearers, trauma-sufferers and prophets - the voices seem to come from outside: friendly voices, malicious ones, the voice of God or the Devil, the muses of art and literature. In The Voices...