It is then that the foremost detective in the world—made so real by Arthur Conan Doyle—dishes out his famous theory about the mind being an ‘empty attic’ with no ‘elastic walls’: ‘A fool takes in all the lumber of every sort that he comes across, so that the knowledge which might be useful to him gets crowded out, or best is jumbled up with a lot of other things . . . for every addition of knowledge you forget something that you knew before. It is of the highest importance, therefore, not to have useless facts elbowing out the useful ones.’
