““The rules that society chooses to live by have always struck me as especially fascinating,” she said. “There are things one can do but not talk about, and there are things one can talk about but not do. There are things—not apparently gender-related—that men can do, but not women, and there are things women can do, but not men. We live in an invisible maze, and we have all learned where to turn and when, so as to find our way through.”
“Some of the rules are good, Mary, and many are necessary,” Lord Darcy said mildly.
“You misunderstood me, my dear,” Mary of Cumberland told him. “As in magic, where there are absolutely essential words to say and gestures to make or the spell won’t work; so in society there are absolutely essential words to say and gestures to make or we won’t understand each other or trust each other, and it will all come tumbling down around us. The problem is that the rules of society, unlike magic, have never been formalized mathematically, and we don’t know which words are essential to the spell and which are just silly words.””

Source: Ten Little Wizards (1988), Chapter 14 (p. 132)