The Greek philosopher Plato (c. 427–c. 348 bc) found an imaginative way of shining light on the dark side of the human heart. He told the story of a shepherd who innocently discovered a golden ring that had been hidden deep in the earth. One day a great earthquake opened up an ancient mountainside tomb and revealed the ring to the shepherd. By accident he also discovered that the ring had the magical ability to enable the wearer to become invisible at will. Thinking about invisibility, Plato raised this question: If people didn’t have to worry about being caught and…