A waiter sets down the plate and says enjoy your meal, and you say you too, and the waiter goes back to the kitchen, where there is no meal. Almost everyone has done it once and winced. But it isn’t a slip of meaning. A wish has come your way, and the answer to a wish is to send one back, and that answer is right so often, after have a good day and take care and see you soon, that it has been fastened to the turn in the conversation rather than to the words in it. The mouth answers the shape before the ears have checked what was inside. What makes it hard to stay embarrassed is that nothing unkind got through. Everything you meant arrived. It was just addressed to a meal that wasn’t there.