Scrooge doesn’t change because he’s frightened – he changes because he’s haunted. We can be frightened of gaining weight, but that alone probably won’t cause us to change our diet. Haunting is different. It makes us feel – makes us alive to – some fact about the world, some piece of information, that we’re trying to avoid. What knowledge is Scrooge trying to avoid? Scrooge doesn’t want to think about the death of his mother, the death of his sister, or the loss of his fiancée – he cannot bear the thought that love ends.
