As dear Erasmus said in De Civilitate, “It is safe to admit nothing that might embarrass one if repeated.” Gossip - Judith Martin

How do you do?” depending on the formality of the occasion, and whether you can count on the other person to understand that the answer to “How do you do?” is “How do you do?” even though that makes two questions in a row. (Etiquette opposes any declaration of being pleased to meet someone on the cynical grounds that it may not turn out to be a pleasure.) The

Miss Manners’ mother always told her to travel either first or third class, but never second, when crossing. (Not crossing class lines, silly; crossing the Atlantic Ocean, in the days when that was done properly, with bouillon at eleven on the promenade deck and tea at five in the salon.) In first class, in those days, you had luxury; in third class, you had fun. This is the proper distribution of the world’s blessings. In second class, you had neither. Naturally, then, someone invented the one-class ship, where the advantages of second class could be enjoyed by all, which is probably why we have those overanxious things called airplanes for crossings these days.

As dear Erasmus said, “It is part of the highest civility if, while never erring yourself, you ignore the errors of others.” Besides, it is a law of nature that he who corrects others will soon do something perfectly awful himself.