“There is a traditional optimistic story that runs as follows. Our hero is a prisoner who has been sentenced to death by a tyrannical king, but gains a reprieve by promising to teach the king’s favourite horse to talk within a year. That night, a fellow prisoner asks what possessed him to make such a bargain. He replies, ‘A lot can happen in a year. The horse might die. The king might die. I might die. Or the horse might talk!”