In civilized life domestic hatred usually expresses itself by saying things which would appear quite harmless on paper (the words are not offensive) but in such a voice, or at such a moment, that they are not far short of a blow in the face. To keep this game up you and Glubose must see to it that each of these two fools has a sort of double standard. Your patient must demand that all his own utterances are to be taken at their face value and judged simply on the actual words, while at the same judging all his mother’s utterances with the fullest and most over-sensitive interpretation of the tone and the context and the suspected intention. She must be encouraged to do the same to him. Hence from every quarrel they can both go away convinced, or very nearly convinced, that they are quite innocent. You know the kind of thing: ‘I simply ask her what time dinner will be and she flies into a temper.’ Once this habit is well established you have the delightful situation of a human saying things with the express purpose of offending and yet having a grievance when offence is taken.
Screwtape (a senior devil) to his nephew Wormwood – C. S. Lewis, The Screwtape Letters