Consider this: when you stand at the entry to a steel factory, you can make out through the smoke some men, some metal, the fires. The furnaces roar, the hammers crash; and the metalworkers who forge ingots, weapons, tools, and so on are completely ignorant of the real uses to which their products will be put. The workers can only refer to their products by conventional names. Well, that's where we all stand, all of us! Nobody can see the real character of what he creates because every knife blade may become a dagger, and the use to which an object is put changes both its name and its nature. Only our ignorance shields us from terrible responsibilities.