It falls to the lot of every teacher of Latin at some time to enunciate the rule, ‘If a question expects the answer “yes”, use nonne; if it expects “no”, use num’; and then, unless he is teaching a class of dummies, the trouble begins. ‘What if you don't expect any particular answer?’ ‘Why, if there are only two possible answers to a question, should there be three ways of asking one?’ ‘What if you don't get the answer you expect? Do you have to go back and amend the question?’