Imagine that this experience happened to you. What would you think as you struggled to cope? What would you think once your heart stopped pounding and the smell of the creature left your nostrils? Would you comfort yourself with the thought that the menacing black ﬁ gure wasn’t real at all and was only imagined? Or might you decide that it was an alien come to abduct you, or perhaps the ghost of someone who had died? Either way you face a problem. If the creature was real, why did the door remained closed and the bed covers undisturbed? Why did no one else see the creature coming through the house? Obviously it wasn’t real in that public sense. On the other hand if it was only imagined, how could it have such a powerful effect on you, and make your heart pound and your hands sweat? Obviously something happened to you, and the experience itself was real enough wasn’t it? Thinking this way can make us deeply confused about the difference between reality and imagination.