It is assumed that there is a difference between sanity and madness, and a difference, which the theatrical illusion depends upon, between being mad and acting the part of a mad person. If we began to have the feeling that the people playing, as we say, Lear or the Macbeths were really as mad as they seem to be in their plays, being a member of the audience would become very much more disturbing. Of course there are good reasons why Goneril and Regan, or the Macbeths, are not going to harm us, but what terrorizes us about the mad is their unpredictability;
